QEMU(1) QEMU QEMU(1)
NAME
qemu - QEMU User Documentation
SYNOPSIS
qemu-system-x86_64 [options] [disk_image]
DESCRIPTION
The QEMU PC System emulator simulates the following peripherals:
o i440FX host PCI bridge and PIIX3 PCI to ISA bridge
o Cirrus CLGD 5446 PCI VGA card or dummy VGA card with Bochs VESA
extensions (hardware level, including all non standard modes).
o PS/2 mouse and keyboard
o 2 PCI IDE interfaces with hard disk and CD-ROM support
o Floppy disk
o PCI and ISA network adapters
o Serial ports
o IPMI BMC, either and internal or external one
o Creative SoundBlaster 16 sound card
o ENSONIQ AudioPCI ES1370 sound card
o Intel 82801AA AC97 Audio compatible sound card
o Intel HD Audio Controller and HDA codec
o Adlib (OPL2) - Yamaha YM3812 compatible chip
o Gravis Ultrasound GF1 sound card
o CS4231A compatible sound card
o PC speaker
o PCI UHCI, OHCI, EHCI or XHCI USB controller and a virtual USB-1.1
hub.
SMP is supported with a large number of virtual CPUs (upper limit is
configuration dependent).
QEMU uses the PC BIOS from the Seabios project and the Plex86/Bochs
LGPL VGA BIOS.
QEMU uses YM3812 emulation by Tatsuyuki Satoh.
QEMU uses GUS emulation (GUSEMU32 )
by Tibor "TS" Schutz.
Note that, by default, GUS shares IRQ(7) with parallel ports and so
QEMU must be told to not have parallel ports to have working GUS.
qemu-system-x86_64 dos.img -device gus -parallel none
Alternatively:
qemu-system-x86_64 dos.img -device gus,irq=5
Or some other unclaimed IRQ.
CS4231A is the chip used in Windows Sound System and GUSMAX products
The PC speaker audio device can be configured using the pcspk-audiodev
machine property, i.e.
qemu-system-x86_64 some.img -audiodev ,id= -machine pcspk-audiodev=
Machine-specific options
It supports the following machine-specific options:
o x-south-bridge=PIIX3|piix4-isa (Experimental option to select a
particular south bridge. Default: PIIX3)
OPTIONS
disk_image is a raw hard disk image for IDE hard disk 0. Some targets
do not need a disk image.
When dealing with options parameters as arbitrary strings containing
commas, such as in "file=my,file" and "string=a,b", it's necessary to
double the commas. For instance,"-fw_cfg name=z,string=a,,b" will be
parsed as "-fw_cfg name=z,string=a,b".
Standard options
-h Display help and exit
-version
Display version information and exit
-machine [type=]name[,prop=value[,...]]
Select the emulated machine by name. Use -machine help to list
available machines.
For architectures which aim to support live migration
compatibility across releases, each release will introduce a new
versioned machine type. For example, the 2.8.0 release
introduced machine types "pc-i440fx-2.8" and "pc-q35-2.8" for
the x86_64/i686 architectures.
To allow live migration of guests from QEMU version 2.8.0, to
QEMU version 2.9.0, the 2.9.0 version must support the
"pc-i440fx-2.8" and "pc-q35-2.8" machines too. To allow users
live migrating VMs to skip multiple intermediate releases when
upgrading, new releases of QEMU will support machine types from
many previous versions.
Supported machine properties are:
accel=accels1[:accels2[:...]]
This is used to enable an accelerator. Depending on the
target architecture, kvm, xen, hvf, nitro, nvmm, whpx,
mshv or tcg can be available. By default, tcg is used. If
there is more than one accelerator specified, the next
one is used if the previous one fails to initialize.
vmport=on|off|auto
Enables emulation of VMWare IO port, for vmmouse etc.
auto says to select the value based on accel and i8042.
For accel=xen or i8042=off the default is off otherwise
the default is on.
dump-guest-core=on|off
Include guest memory in a core dump. The default is on.
mem-merge=on|off
Enables or disables memory merge support. This feature,
when supported by the host, de-duplicates identical
memory pages among VMs instances (enabled by default).
aes-key-wrap=on|off
Enables or disables AES key wrapping support on s390-ccw
hosts. This feature controls whether AES wrapping keys
will be created to allow execution of AES cryptographic
functions. The default is on.
dea-key-wrap=on|off
Enables or disables DEA key wrapping support on s390-ccw
hosts. This feature controls whether DEA wrapping keys
will be created to allow execution of DEA cryptographic
functions. The default is on.
nvdimm=on|off
Enables or disables NVDIMM support. The default is off.
memory-encryption=
Memory encryption object to use. The default is none.
hmat=on|off
Enables or disables ACPI Heterogeneous Memory Attribute
Table (HMAT) support. The default is off.
spcr=on|off
Enables or disables ACPI Serial Port Console Redirection
Table (SPCR) support. The default is on.
aux-ram-share=on|off
Allocate auxiliary guest RAM as an anonymous file that is
shareable with an external process. This option applies
to memory allocated as a side effect of creating various
devices. It does not apply to memory-backend-objects,
whether explicitly specified on the command line, or
implicitly created by the -m command line option. The
default is off.
To use the cpr-transfer migration mode, you must set
aux-ram-share=on.
memory-backend='id'
An alternative to legacy -mem-path and mem-prealloc
options. Allows to use a memory backend as main RAM.
For example:
-object memory-backend-file,id=pc.ram,size=512M,mem-path=/hugetlbfs,prealloc=on,share=on
-machine memory-backend=pc.ram
-m 512M
Migration compatibility note:
o as backend id one shall use value of 'default-ram-id',
advertised by machine type (available via
query-machines QMP command), if migration to/from old
QEMU (<5.0) is expected.
o for machine types 4.0 and older, user shall use
x-use-canonical-path-for-ramblock-id=off backend option
if migration to/from old QEMU (<5.0) is expected.
For example:
-object memory-backend-ram,id=pc.ram,size=512M,x-use-canonical-path-for-ramblock-id=off
-machine memory-backend=pc.ram
-m 512M
cxl-fmw.0.targets.0=firsttarget,cxl-fmw.0.targets.1=secondtarget,cxl-fmw.0.size=size[,cxl-fmw.0.interleave-granularity=granularity]
Define a CXL Fixed Memory Window (CFMW).
Described in the CXL 2.0 ECN: CEDT CFMWS & QTG _DSM.
They are regions of Host Physical Addresses (HPA) on a
system which may be interleaved across one or more CXL
host bridges. The system software will assign particular
devices into these windows and configure the downstream
Host-managed Device Memory (HDM) decoders in root ports,
switch ports and devices appropriately to meet the
interleave requirements before enabling the memory
devices.
targets.X=target provides the mapping to CXL host bridges
which may be identified by the id provided in the -device
entry. Multiple entries are needed to specify all the
targets when the fixed memory window represents
interleaved memory. X is the target index from 0.
size=size sets the size of the CFMW. This must be a
multiple of 256MiB. The region will be aligned to 256MiB
but the location is platform and configuration dependent.
interleave-granularity=granularity sets the granularity
of interleave. Default 256 (bytes). Only 256, 512, 1k,
2k, 4k, 8k and 16k granularities supported.
Example:
-machine cxl-fmw.0.targets.0=cxl.0,cxl-fmw.0.targets.1=cxl.1,cxl-fmw.0.size=128G,cxl-fmw.0.interleave-granularity=512
sgx-epc.0.memdev=,sgx-epc.0.node=
Define an SGX EPC section.
smp-cache.0.cache=cachename,smp-cache.0.topology=topologylevel
Define cache properties for SMP system.
cache=cachename specifies the cache that the properties
will be applied on. This field is the combination of
cache level and cache type. It supports l1d (L1 data
cache), l1i (L1 instruction cache), l2 (L2 unified cache)
and l3 (L3 unified cache).
topology=topologylevel sets the cache topology level. It
accepts CPU topology levels including core, module,
cluster, die, socket, book, drawer and a special value
default. If default is set, then the cache topology will
follow the architecture's default cache topology model.
If another topology level is set, the cache will be
shared at corresponding CPU topology level. For example,
topology=core makes the cache shared by all threads
within a core. The omitting cache will default to using
the default level.
The default cache topology model for an i386 PC machine
is as follows: l1d, l1i, and l2 caches are per core,
while the l3 cache is per die.
Example:
-machine smp-cache.0.cache=l1d,smp-cache.0.topology=core,smp-cache.1.cache=l1i,smp-cache.1.topology=core
-M as -machine.
-cpu model
Select CPU model (-cpu help for list and additional feature
selection)
-accel name[,prop=value[,...]]
This is used to enable an accelerator. Depending on the target
architecture, kvm, xen, hvf, nitro, nvmm, whpx, mshv or tcg can
be available. By default, tcg is used. If there is more than
one accelerator specified, the next one is used if the previous
one fails to initialize.
igd-passthru=on|off
When Xen is in use, this option controls whether Intel
integrated graphics devices can be passed through to the
guest (default=off)
kernel-irqchip=on|off|split
Controls KVM in-kernel irqchip support. The default is
full acceleration of the interrupt controllers. On x86,
split irqchip reduces the kernel attack surface, at a
performance cost for non-MSI interrupts. Disabling the
in-kernel irqchip completely is not recommended except
for debugging purposes.
kvm-shadow-mem=size
Defines the size of the KVM shadow MMU.
one-insn-per-tb=on|off
Makes the TCG accelerator put only one guest instruction
into each translation block. This slows down emulation a
lot, but can be useful in some situations, such as when
trying to analyse the logs produced by the -d option.
split-wx=on|off
Controls the use of split w^x mapping for the TCG code
generation buffer. Some operating systems require this to
be enabled, and in such a case this will default on. On
other operating systems, this will default off, but one
may enable this for testing or debugging.
tb-size=n
Controls the size (in MiB) of the TCG translation block
cache.
thread=single|multi
Controls number of TCG threads. When the TCG is
multi-threaded there will be one thread per vCPU
therefore taking advantage of additional host cores. The
default is to enable multi-threading where both the
back-end and front-ends support it and no incompatible
TCG features have been enabled (e.g. icount/replay).
dirty-ring-size=n
When the KVM accelerator is used, it controls the size of
the per-vCPU dirty page ring buffer (number of entries
for each vCPU). It should be a value that is power of
two, and it should be 1024 or bigger (but still less than
the maximum value that the kernel supports). 4096 could
be a good initial value if you have no idea which is the
best. Set this value to 0 to disable the feature. By
default, this feature is disabled (dirty-ring-size=0).
When enabled, KVM will instead record dirty pages in a
bitmap.
eager-split-size=n
KVM implements dirty page logging at the PAGE_SIZE
granularity and enabling dirty-logging on a huge-page
requires breaking it into PAGE_SIZE pages in the first
place. KVM on ARM does this splitting lazily by default.
There are performance benefits in doing huge-page split
eagerly, especially in situations where TLBI costs
associated with break-before-make sequences are
considerable and also if guest workloads are read
intensive. The size here specifies how many pages to
break at a time and needs to be a valid block size which
is 1GiB/2MiB/4KiB, 32MiB/16KiB and 512MiB/64KiB for
4KiB/16KiB/64KiB PAGE_SIZE respectively. Be wary of
specifying a higher size as it will have an impact on the
memory. By default, this feature is disabled
(eager-split-size=0).
notify-vmexit=run|internal-error|disable,notify-window=n
Enables or disables notify VM exit support on x86 host
and specify the corresponding notify window to trigger
the VM exit if enabled. run option enables the feature.
It does nothing and continue if the exit happens.
internal-error option enables the feature. It raises a
internal error. disable option doesn't enable the
feature. This feature can mitigate the CPU stuck issue
due to event windows don't open up for a specified of
time (i.e. notify-window). Default:
notify-vmexit=run,notify-window=0.
device=path
Sets the path to the KVM device node. Defaults to
/dev/kvm. This option can be used to pass the KVM device
to use via a file descriptor by setting the value to
/dev/fdset/NN.
hyperv=on|off|auto
For the WHPX backend, determines whether to enable
Hyper-V enlightenments. On x86_64, Hyper-V
enlightenments are on by default. On AArch64, they're off
by default.
-smp
[[cpus=]n][,maxcpus=maxcpus][,drawers=drawers][,books=books][,sockets=sockets][,dies=dies][,clusters=clusters][,modules=modules][,cores=cores][,threads=threads]
Simulate a SMP system with 'n' CPUs initially present on the
machine type board. On boards supporting CPU hotplug, the
optional 'maxcpus' parameter can be set to enable further CPUs
to be added at runtime. When both parameters are omitted, the
maximum number of CPUs will be calculated from the provided
topology members and the initial CPU count will match the
maximum number. When only one of them is given then the omitted
one will be set to its counterpart's value. Both parameters may
be specified, but the maximum number of CPUs must be equal to or
greater than the initial CPU count. Product of the CPU topology
hierarchy must be equal to the maximum number of CPUs. Both
parameters are subject to an upper limit that is determined by
the specific machine type chosen.
To control reporting of CPU topology information, values of the
topology parameters can be specified. Machines may only support
a subset of the parameters and different machines may have
different subsets supported which vary depending on capacity of
the corresponding CPU targets. So for a particular machine type
board, an expected topology hierarchy can be defined through the
supported sub-option. Unsupported parameters can also be
provided in addition to the sub-option, but their values must be
set as 1 in the purpose of correct parsing.
Either the initial CPU count, or at least one of the topology
parameters must be specified. The specified parameters must be
greater than zero, explicit configuration like "cpus=0" is not
allowed. Values for any omitted parameters will be computed from
those which are given.
For example, the following sub-option defines a CPU topology
hierarchy (2 sockets totally on the machine, 2 cores per socket,
2 threads per core) for a machine that only supports
sockets/cores/threads. Some members of the option can be
omitted but their values will be automatically computed:
-smp 8,sockets=2,cores=2,threads=2,maxcpus=8
The following sub-option defines a CPU topology hierarchy (2
sockets totally on the machine, 2 dies per socket, 2 modules per
die, 2 cores per module, 2 threads per core) for PC machines
which support sockets/dies /modules/cores/threads. Some members
of the option can be omitted but their values will be
automatically computed:
-smp 32,sockets=2,dies=2,modules=2,cores=2,threads=2,maxcpus=32
The following sub-option defines a CPU topology hierarchy (2
sockets totally on the machine, 2 clusters per socket, 2 cores
per cluster, 2 threads per core) for ARM virt machines which
support sockets/clusters /cores/threads. Some members of the
option can be omitted but their values will be automatically
computed:
-smp 16,sockets=2,clusters=2,cores=2,threads=2,maxcpus=16
Historically preference was given to the coarsest topology
parameters when computing missing values (ie sockets preferred
over cores, which were preferred over threads), however, this
behaviour is considered liable to change. Prior to 6.2 the
preference was sockets over cores over threads. Since 6.2 the
preference is cores over sockets over threads.
For example, the following option defines a machine board with 2
sockets of 1 core before 6.2 and 1 socket of 2 cores after 6.2:
-smp 2
Note: The cluster topology will only be generated in ACPI and
exposed to guest if it's explicitly specified in -smp.
-numa
node[,mem=size][,cpus=firstcpu[-lastcpu]][,nodeid=node][,initiator=initiator]
-numa
node[,memdev=id][,cpus=firstcpu[-lastcpu]][,nodeid=node][,initiator=initiator]
-numa dist,src=source,dst=destination,val=distance
-numa cpu,node-id=node[,socket-id=x][,core-id=y][,thread-id=z]
-numa
hmat-lb,initiator=node,target=node,hierarchy=hierarchy,data-type=type[,latency=lat][,bandwidth=bw]
-numa
hmat-cache,node-id=node,size=size,level=level[,associativity=str][,policy=str][,line=size]
Define a NUMA node and assign RAM and VCPUs to it. Set the NUMA
distance from a source node to a destination node. Set the ACPI
Heterogeneous Memory Attributes for the given nodes.
Legacy VCPU assignment uses 'cpus' option where firstcpu and
lastcpu are CPU indexes. Each 'cpus' option represent a
contiguous range of CPU indexes (or a single VCPU if lastcpu is
omitted). A non-contiguous set of VCPUs can be represented by
providing multiple 'cpus' options. If 'cpus' is omitted on all
nodes, VCPUs are automatically split between them.
For example, the following option assigns VCPUs 0, 1, 2 and 5 to
a NUMA node:
-numa node,cpus=0-2,cpus=5
'cpu' option is a new alternative to 'cpus' option which uses
'socket-id|core-id|thread-id' properties to assign CPU objects
to a node using topology layout properties of CPU. The set of
properties is machine specific, and depends on used machine
type/'smp' options. It could be queried with 'hotpluggable-cpus'
monitor command. 'node-id' property specifies node to which CPU
object will be assigned, it's required for node to be declared
with 'node' option before it's used with 'cpu' option.
For example:
-M pc \
-smp 1,sockets=2,maxcpus=2 \
-numa node,nodeid=0 -numa node,nodeid=1 \
-numa cpu,node-id=0,socket-id=0 -numa cpu,node-id=1,socket-id=1
'memdev' option assigns RAM from a given memory backend device
to a node. It is recommended to use 'memdev' option over legacy
'mem' option. This is because 'memdev' option provides better
performance and more control over the backend's RAM (e.g.
'prealloc' parameter of '-memory-backend-ram' allows memory
preallocation).
For compatibility reasons, legacy 'mem' option is supported in
5.0 and older machine types. Note that 'mem' and 'memdev' are
mutually exclusive. If one node uses 'memdev', the rest nodes
have to use 'memdev' option, and vice versa.
Users must specify memory for all NUMA nodes by 'memdev' (or
legacy 'mem' if available). In QEMU 5.2, the support for '-numa
node' without memory specified was removed.
'initiator' is an additional option that points to an initiator
NUMA node that has best performance (the lowest latency or
largest bandwidth) to this NUMA node. Note that this option can
be set only when the machine property 'hmat' is set to 'on'.
Following example creates a machine with 2 NUMA nodes, node 0
has CPU. node 1 has only memory, and its initiator is node 0.
Note that because node 0 has CPU, by default the initiator of
node 0 is itself and must be itself.
-machine hmat=on \
-m 2G,slots=2,maxmem=4G \
-object memory-backend-ram,size=1G,id=m0 \
-object memory-backend-ram,size=1G,id=m1 \
-numa node,nodeid=0,memdev=m0 \
-numa node,nodeid=1,memdev=m1,initiator=0 \
-smp 2,sockets=2,maxcpus=2 \
-numa cpu,node-id=0,socket-id=0 \
-numa cpu,node-id=0,socket-id=1
source and destination are NUMA node IDs. distance is the NUMA
distance from source to destination. The distance from a node to
itself is always 10. If any pair of nodes is given a distance,
then all pairs must be given distances. Although, when distances
are only given in one direction for each pair of nodes, then the
distances in the opposite directions are assumed to be the same.
If, however, an asymmetrical pair of distances is given for even
one node pair, then all node pairs must be provided distance
values for both directions, even when they are symmetrical. When
a node is unreachable from another node, set the pair's distance
to 255.
Note that the -numa option doesn't allocate any of the specified
resources, it just assigns existing resources to NUMA nodes.
This means that one still has to use the -m, -smp options to
allocate RAM and VCPUs respectively.
Use 'hmat-lb' to set System Locality Latency and Bandwidth
Information between initiator and target NUMA nodes in ACPI
Heterogeneous Attribute Memory Table (HMAT). Initiator NUMA node
can create memory requests, usually it has one or more
processors. Target NUMA node contains addressable memory.
In 'hmat-lb' option, node are NUMA node IDs. hierarchy is the
memory hierarchy of the target NUMA node: if hierarchy is
'memory', the structure represents the memory performance; if
hierarchy is 'first-level|second-level|third-level', this
structure represents aggregated performance of memory side
caches for each domain. type of 'data-type' is type of data
represented by this structure instance: if 'hierarchy' is
'memory', 'data-type' is 'access|read|write' latency or
'access|read|write' bandwidth of the target memory; if
'hierarchy' is 'first-level|second-level|third-level',
'data-type' is 'access|read|write' hit latency or
'access|read|write' hit bandwidth of the target memory side
cache.
lat is latency value in nanoseconds. bw is bandwidth value, the
possible value and units are NUM[M|G|T], mean that the bandwidth
value are NUM byte per second (or MiB/s, GiB/s or TiB/s
depending on used suffix). Note that if latency or bandwidth
value is 0, means the corresponding latency or bandwidth
information is not provided.
In 'hmat-cache' option, node-id is the NUMA-id of the memory
belongs. size is the size of memory side cache in bytes. level
is the cache level described in this structure, note that the
cache level 0 should not be used with 'hmat-cache' option.
associativity is the cache associativity, the possible value is
'none/direct(direct-mapped)/complex(complex cache indexing)'.
policy is the write policy. line is the cache Line size in
bytes.
For example, the following options describe 2 NUMA nodes. Node 0
has 2 cpus and a ram, node 1 has only a ram. The processors in
node 0 access memory in node 0 with access-latency 5
nanoseconds, access-bandwidth is 200 MiB/s; The processors in
NUMA node 0 access memory in NUMA node 1 with access-latency 10
nanoseconds, access-bandwidth is 100 MiB/s. And for memory side
cache information, NUMA node 0 and 1 both have 1 level memory
cache, size is 10KiB, policy is write-back, the cache Line size
is 8 bytes:
-machine hmat=on \
-m 2G \
-object memory-backend-ram,size=1G,id=m0 \
-object memory-backend-ram,size=1G,id=m1 \
-smp 2,sockets=2,maxcpus=2 \
-numa node,nodeid=0,memdev=m0 \
-numa node,nodeid=1,memdev=m1,initiator=0 \
-numa cpu,node-id=0,socket-id=0 \
-numa cpu,node-id=0,socket-id=1 \
-numa hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-latency,latency=5 \
-numa hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-bandwidth,bandwidth=200M \
-numa hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-latency,latency=10 \
-numa hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-bandwidth,bandwidth=100M \
-numa hmat-cache,node-id=0,size=10K,level=1,associativity=direct,policy=write-back,line=8 \
-numa hmat-cache,node-id=1,size=10K,level=1,associativity=direct,policy=write-back,line=8
-add-fd fd=fd,set=set[,opaque=opaque]
Add a file descriptor to an fd set. Valid options are:
fd=fd This option defines the file descriptor of which a
duplicate is added to fd set. The file descriptor cannot
be stdin, stdout, or stderr.
set=set
This option defines the ID of the fd set to add the file
descriptor to.
opaque=opaque
This option defines a free-form string that can be used
to describe fd.
You can open an image using pre-opened file descriptors from an
fd set:
qemu-system-x86_64 \
-add-fd fd=3,set=2,opaque="rdwr:/path/to/file" \
-add-fd fd=4,set=2,opaque="rdonly:/path/to/file" \
-drive file=/dev/fdset/2,index=0,media=disk
-set group.id.arg=value
Set parameter arg for item id of type group
-global driver.prop=value
-global driver=driver,property=property,value=value
Set default value of driver's property prop to value, e.g.:
qemu-system-x86_64 -global ide-hd.physical_block_size=4096 disk-image.img
In particular, you can use this to set driver properties for
devices which are created automatically by the machine model. To
create a device which is not created automatically and set
properties on it, use -device.
-global driver.prop=value is shorthand for -global
driver=driver,property=prop,value=value. The longhand syntax
works even when driver contains a dot.
-boot
[order=drives][,once=drives][,menu=on|off][,splash=sp_name][,splash-time=sp_time][,reboot-timeout=rb_timeout][,strict=on|off]
Specify boot order drives as a string of drive letters. Valid
drive letters depend on the target architecture. The x86 PC
uses: a, b (floppy 1 and 2), c (first hard disk), d (first
CD-ROM), n-p (Etherboot from network adapter 1-4), hard disk
boot is the default. To apply a particular boot order only on
the first startup, specify it via once. Note that the order or
once parameter should not be used together with the bootindex
property of devices, since the firmware implementations normally
do not support both at the same time.
Interactive boot menus/prompts can be enabled via menu=on as far
as firmware/BIOS supports them. The default is non-interactive
boot.
A splash picture could be passed to bios, enabling user to show
it as logo, when option splash=sp_name is given and menu=on, If
firmware/BIOS supports them. Currently Seabios for X86 system
support it. limitation: The splash file could be a jpeg file or
a BMP file in 24 BPP format(true color). The resolution should
be supported by the SVGA mode, so the recommended is 320x240,
640x480, 800x640.
A timeout could be passed to bios, guest will pause for
rb_timeout ms when boot failed, then reboot. If rb_timeout is
'-1', guest will not reboot, qemu passes '-1' to bios by
default. Currently Seabios for X86 system support it.
Do strict boot via strict=on as far as firmware/BIOS supports
it. This only effects when boot priority is changed by bootindex
options. The default is non-strict boot.
# try to boot from network first, then from hard disk
qemu-system-x86_64 -boot order=nc
# boot from CD-ROM first, switch back to default order after reboot
qemu-system-x86_64 -boot once=d
# boot with a splash picture for 5 seconds.
qemu-system-x86_64 -boot menu=on,splash=/root/boot.bmp,splash-time=5000
Note: The legacy format '-boot drives' is still supported but
its use is discouraged as it may be removed from future
versions.
-m [size=]megs[,slots=n,maxmem=size]
Sets guest startup RAM size to megs megabytes. Default is 128
MiB. Optionally, a suffix of "M" or "G" can be used to signify
a value in megabytes or gigabytes respectively. Optional pair
slots, maxmem could be used to set amount of hotpluggable memory
slots and maximum amount of memory. Note that maxmem must be
aligned to the page size.
For example, the following command-line sets the guest startup
RAM size to 1GiB, creates 3 slots to hotplug additional memory
and sets the maximum memory the guest can reach to 4GiB:
qemu-system-x86_64 -m 1G,slots=3,maxmem=4G
If slots and maxmem are not specified, memory hotplug won't be
enabled and the guest startup RAM will never increase.
-mem-path path
Allocate guest RAM from a temporarily created file in path.
-mem-prealloc
Preallocate memory when using -mem-path.
-k language
Use keyboard layout language (for example fr for French). This
option is only needed where it is not easy to get raw PC
keycodes (e.g. on Macs, with some X11 servers or with a VNC or
curses display). You don't normally need to use it on PC/Linux
or PC/Windows hosts.
The available layouts are:
ar de-ch es fo fr-ca hu ja mk no pt-br sv
da en-gb et fr fr-ch is lt nl pl ru th
de en-us fi fr-be hr it lv nl-be pt sl tr
The default is en-us.
-audio [driver=]driver[,model=value][,prop=value[,...]]
If the model option is specified, -audio is a shortcut for
configuring both the guest audio hardware and the host audio
backend in one go. The guest hardware model can be set with
model=modelname. Use model=help to list the available device
types.
The following two example do exactly the same, to show how
-audio can be used to shorten the command line length:
qemu-system-x86_64 -audiodev pa,id=pa -device sb16,audiodev=pa
qemu-system-x86_64 -audio pa,model=sb16
If the model option is not specified, -audio is used to
configure a default audio backend that will be used whenever the
audiodev property is not set on a device or machine. In
particular, -audio none ensures that no audio is produced even
for machines that have embedded sound hardware.
In both cases, the driver option is the same as with the
corresponding -audiodev option below. Use driver=help to list
the available drivers.
-audiodev [driver=]driver,id=id[,prop=value[,...]]
Adds a new audio backend driver identified by id.
If no audio backend is specified, QEMU will attempt to select a
default one. The -display option may influence which backend is
selected.
There are global and driver specific properties. Some values can
be set differently for input and output, they're marked with
in|out.. You can set the input's property with in.prop and the
output's property with out.prop. For example:
-audiodev alsa,id=example,in.frequency=44110,out.frequency=8000
-audiodev alsa,id=example,out.channels=1 # leaves in.channels unspecified
NOTE: parameter validation is known to be incomplete, in many
cases specifying an invalid option causes QEMU to print an error
message and continue emulation without sound.
Valid global options are:
id=identifier
Identifies the audio backend.
timer-period=period
Sets the timer period used by the audio subsystem in
microseconds. Default is 10000 (10 ms).
in|out.mixing-engine=on|off
Use QEMU's mixing engine to mix all streams inside QEMU
and convert audio formats when not supported by the
backend. When off, fixed-settings must be off too. Note
that disabling this option means that the selected
backend must support multiple streams and the audio
formats used by the virtual cards, otherwise you'll get
no sound. It's not recommended to disable this option
unless you want to use 5.1 or 7.1 audio, as mixing engine
only supports mono and stereo audio. Default is on.
in|out.fixed-settings=on|off
Use fixed settings for host audio. When off, it will
change based on how the guest opens the sound card. In
this case you must not specify frequency, channels or
format. Default is on.
in|out.frequency=frequency
Specify the frequency to use when using fixed-settings.
Default is 44100Hz.
in|out.channels=channels
Specify the number of channels to use when using
fixed-settings. Default is 2 (stereo).
in|out.format=format
Specify the sample format to use when using
fixed-settings. Valid values are: s8, s16, s32, u8, u16,
u32, f32. Default is s16.
in|out.voices=voices
Specify the number of voices to use. Default is 1.
in|out.buffer-length=usecs
Sets the size of the buffer in microseconds.
-audiodev none,id=id[,prop=value[,...]]
Creates a dummy backend that discards all outputs. This backend
has no backend specific properties.
-audiodev alsa,id=id[,prop=value[,...]]
Creates backend using the ALSA. This backend is only available
on Linux.
ALSA specific options are:
in|out.dev=device
Specify the ALSA device to use for input and/or output.
Default is default.
in|out.period-length=usecs
Sets the period length in microseconds.
in|out.try-poll=on|off
Attempt to use poll mode with the device. Default is off.
threshold=threshold
Threshold (in microseconds) when playback starts. Default
is 0.
-audiodev coreaudio,id=id[,prop=value[,...]]
Creates a backend using Apple's Core Audio. This backend is only
available on Mac OS and only supports playback.
Core Audio specific options are:
in|out.buffer-count=count
Sets the count of the buffers.
-audiodev dbus,id=id[,prop=value[,...]]
Creates a D-Bus backend. It must be associated with the display
(as -display dbus,audiodev=id). (Since 7.0)
D-Bus specific options are:
nsamples
Number of samples per read/write (default to 480, 10ms at
48kHz) (Since 10.0)
-audiodev dsound,id=id[,prop=value[,...]]
Creates a backend using Microsoft's DirectSound. This backend is
only available on Windows and only supports playback.
DirectSound specific options are:
latency=usecs
Add extra usecs microseconds latency to playback. Default
is 10000 (10 ms).
-audiodev oss,id=id[,prop=value[,...]]
Creates a backend using OSS. This backend is available on most
Unix-like systems.
OSS specific options are:
in|out.dev=device
Specify the file name of the OSS device to use. Default
is /dev/dsp.
in|out.buffer-count=count
Sets the count of the buffers.
in|out.try-poll=on|off
Attempt to use poll mode with the device. Default is on.
try-mmap=on|off
Try using memory mapped device access. Default is off.
exclusive=on|off
Open the device in exclusive mode (vmix won't work in
this case). Default is off.
dsp-policy=policy
Sets the timing policy (between 0 and 10, where smaller
number means smaller latency but higher CPU usage). Use
-1 to use buffer sizes specified by buffer and
buffer-count. This option is ignored if you do not have
OSS 4. Default is 5.
-audiodev pa,id=id[,prop=value[,...]]
Creates a backend using PulseAudio. This backend is available on
most systems.
PulseAudio specific options are:
server=server
Sets the PulseAudio server to connect to.
in|out.name=sink
Use the specified source/sink for recording/playback.
in|out.latency=usecs
Desired latency in microseconds. The PulseAudio server
will try to honor this value but actual latencies may be
lower or higher.
-audiodev pipewire,id=id[,prop=value[,...]]
Creates a backend using PipeWire. This backend is available on
most systems.
PipeWire specific options are:
in|out.latency=usecs
Desired latency in microseconds.
in|out.name=sink
Use the specified source/sink for recording/playback.
in|out.stream-name
Specify the name of pipewire stream.
-audiodev sdl,id=id[,prop=value[,...]]
Creates a backend using SDL. This backend is available on most
systems, but you should use your platform's native backend if
possible.
SDL specific options are:
in|out.buffer-count=count
Sets the count of the buffers.
-audiodev sndio,id=id[,prop=value[,...]]
Creates a backend using SNDIO. This backend is available on
OpenBSD and most other Unix-like systems.
Sndio specific options are:
in|out.dev=device
Specify the sndio device to use for input and/or output.
Default is default.
in|out.latency=usecs
Sets the desired period length in microseconds.
-audiodev spice,id=id[,prop=value[,...]]
Creates a backend that sends audio through SPICE. This backend
requires -spice and automatically selected in that case, so
usually you can ignore this option. This backend has no backend
specific properties.
-audiodev wav,id=id[,prop=value[,...]]
Creates a backend that writes audio to a WAV file.
Backend specific options are:
path=path
Write recorded audio into the specified file. Default is
qemu.wav.
-device driver[,prop=value[,...]]
Add device driver. prop=value sets driver properties. Valid
properties depend on the driver. To get help on possible drivers
and properties, use -device help and -device driver,help.
Some drivers are:
-device ipmi-bmc-sim,id=id[,prop=value[,...]]
Add an IPMI BMC. This is a simulation of a hardware management
interface processor that normally sits on a system. It provides
a watchdog and the ability to reset and power control the
system. You need to connect this to an IPMI interface to make it
useful
The IPMI slave address to use for the BMC. The default is 0x20.
This address is the BMC's address on the I2C network of
management controllers. If you don't know what this means, it is
safe to ignore it.
id=id The BMC id for interfaces to use this device.
slave_addr=val
Define slave address to use for the BMC. The default is
0x20.
sdrfile=file
file containing raw Sensor Data Records (SDR) data. The
default is none.
fruareasize=val
size of a Field Replaceable Unit (FRU) area. The default
is 1024.
frudatafile=file
file containing raw Field Replaceable Unit (FRU)
inventory data. The default is none.
guid=uuid
value for the GUID for the BMC, in standard UUID format.
If this is set, get "Get GUID" command to the BMC will
return it. Otherwise "Get GUID" will return an error.
lan.channel=val
channel number of the fake LAN channel. It can be 0 or
any integer from 0x1 to 0xb inclusive. If set to 0, the
LAN channel is disabled, otherwise the LAN channel is
enabled at the specified channel number. The default is
0.
lan.ipaddr=addr
the ipv4 address of the BMC LAN channel.
lan.ipsrc=val
the ipv4 address source of the BMC LAN channel. It can be
0 (unspecified source), 1 (static address), 2 (DHCP), 3
(BIOS or system software), or 4 (other source). The
default is 0.
lan.macaddr=mac
the mac address of the BMC LAN channel.
lan.netmask=mask
the ipv4 subnet mask for the BMC LAN channel.
lan.defgw_ipaddr=addr
the default gateway ipv4 address for the BMC LAN channel.
lan.defgw_macaddr=mac
the default gateway mac address for the BMC LAN channel.
-device ipmi-bmc-extern,id=id,chardev=id[,slave_addr=val]
Add a connection to an external IPMI BMC simulator. Instead of
locally emulating the BMC like the above item, instead connect
to an external entity that provides the IPMI services.
A connection is made to an external BMC simulator. If you do
this, it is strongly recommended that you use the
"reconnect-ms=" chardev option to reconnect to the simulator if
the connection is lost. Note that if this is not used carefully,
it can be a security issue, as the interface has the ability to
send resets, NMIs, and power off the VM. It's best if QEMU makes
a connection to an external simulator running on a secure port
on localhost, so neither the simulator nor QEMU is exposed to
any outside network.
See the "lanserv/README.vm" file in the OpenIPMI library for
more details on the external interface.
-device isa-ipmi-kcs,bmc=id[,ioport=val][,irq=val]
Add a KCS IPMI interface on the ISA bus. This also adds a
corresponding ACPI and SMBIOS entries, if appropriate.
bmc=id The BMC to connect to, one of ipmi-bmc-sim or
ipmi-bmc-extern above.
ioport=val
Define the I/O address of the interface. The default is
0xca0 for KCS.
irq=val
Define the interrupt to use. The default is 5. To disable
interrupts, set this to 0.
-device isa-ipmi-bt,bmc=id[,ioport=val][,irq=val]
Like the KCS interface, but defines a BT interface. The default
port is 0xe4 and the default interrupt is 5.
-device pci-ipmi-kcs,bmc=id
Add a KCS IPMI interface on the PCI bus.
bmc=id The BMC to connect to, one of ipmi-bmc-sim or
ipmi-bmc-extern above.
-device pci-ipmi-bt,bmc=id
Like the KCS interface, but defines a BT interface on the PCI
bus.
-device intel-iommu[,option=...]
This is only supported by -machine q35, which will enable Intel
VT-d emulation within the guest. It supports below options:
intremap=on|off (default: auto)
This enables interrupt remapping feature. It's required
to enable complete x2apic. Currently it only supports
kvm kernel-irqchip modes off or split, while full
kernel-irqchip is not yet supported. The default value
is "auto", which will be decided by the mode of
kernel-irqchip.
caching-mode=on|off (default: off)
This enables caching mode for the VT-d emulated device.
When caching-mode is enabled, each guest DMA buffer
mapping will generate an IOTLB invalidation from the
guest IOMMU driver to the vIOMMU device in a synchronous
way. It is required for -device vfio-pci to work with
the VT-d device, because host assigned devices requires
to setup the DMA mapping on the host before guest DMA
starts.
device-iotlb=on|off (default: off)
This enables device-iotlb capability for the emulated
VT-d device. So far virtio/vhost should be the only real
user for this parameter, paired with ats=on configured
for the device.
aw-bits=39|48 (default: 39)
This decides the address width of IOVA address space.
The address space has 39 bits width for 3-level IOMMU
page tables, and 48 bits for 4-level IOMMU page tables.
Please also refer to the wiki page for general scenarios of VT-d
emulation in QEMU: .
-device virtio-iommu-pci[,option=...]
This is only supported by -machine q35 (x86_64) and -machine
virt (ARM). It supports below options:
granule=val (possible values are 4k, 8k, 16k, 64k and host;
default: host)
This decides the default granule to be be exposed by the
virtio-iommu. If host, the granule matches the host page
size.
aw-bits=val (val between 32 and 64, default depends on machine)
This decides the address width of the IOVA address space.
-device arm-smmuv3,primary-bus=id[,option=...]
This is only supported by -machine virt (ARM).
primary-bus=id
Accepts either the default root complex (pcie.0) or a
pxb-pcie based root complex.
accel=on|off (default: off)
Enables guest to leverage host SMMUv3 features for
acceleration. Enabling accel configures the host
SMMUv3 in nested mode to support vfio-pci passthrough.
The following options are available when accel=on. Note:
'auto' mode is not currently supported.
ril=on|off (default: on)
Support for Range Invalidation, which allows the SMMUv3
driver to invalidate TLB entries for a range of IOVAs at
once instead of issuing separate commands to invalidate
each page. Must match with host SMMUv3 Range Invalidation
support.
ats=on|off (default: off)
Support for Address Translation Services, which enables
PCIe devices to cache address translations in their local
TLB and reduce latency. Host SMMUv3 must support ATS in
order to enable this feature for the vIOMMU.
oas=val (supported values are 44 and 48. default: 44)
Sets the Output Address Size in bits. The value set here
must be less than or equal to the host SMMUv3's supported
OAS, so that the intermediate physical addresses (IPA)
consumed by host SMMU for stage-2 translation do not
exceed the host's max supported IPA size.
ssidsize=val (val between 0 and 20. default: 0)
Sets the Substream ID size in bits. When set to a
non-zero value, PASID capability is advertised to the
vIOMMU and accelerated use cases such as Shared Virtual
Addressing (SVA) are supported.
-device amd-iommu[,option=...]
Enables emulation of an AMD-Vi I/O Memory Management Unit
(IOMMU). Only available with -machine q35, it supports the
following options:
dma-remap=on|off (default: off)
Support for DMA address translation and access permission
checking for guests attaching passthrough devices to
paging domains, using the AMD v1 I/O Page Table format.
This enables -device vfio-pci,... to work correctly with
a guest using the DMA remapping feature of the vIOMMU.
intremap=on|off (default: auto)
Generic x86 IOMMU functionality implemented by amd-iommu
device. Enables interrupt remapping feature in guests,
which is also required to enable x2apic support.
Currently only available with kernel-irqchip=off|split,
it is automatically enabled when either of those modes is
in use, and disabled with kernel-irqchip=on.
xtsup=on|off (default: off)
Interrupt remapping table supports x2apic mode, enabling
the use of 128-bit IRTE format with 32-bit destination
field by the guest. Required to support routing
interrupts to vCPUs with APIC IDs larger than 0xff.
-name name
Sets the name of the guest. This name will be displayed in the
SDL window caption. The name will also be used for the VNC
server. Also optionally set the top visible process name in
Linux. Naming of individual threads can also be enabled on Linux
to aid debugging.
-uuid uuid
Set system UUID.
Block device options
The QEMU block device handling options have a long history and have
gone through several iterations as the feature set and complexity of
the block layer have grown. Many online guides to QEMU often reference
older and deprecated options, which can lead to confusion.
The most explicit way to describe disks is to use a combination of
-device to specify the hardware device and -blockdev to describe the
backend. The device defines what the guest sees and the backend
describes how QEMU handles the data. It is the only guaranteed stable
interface for describing block devices and as such is recommended for
management tools and scripting.
The -drive option combines the device and backend into a single command
line option which is a more human friendly. There is however no
interface stability guarantee although some older board models still
need updating to work with the modern blockdev forms.
Older options like -hda are essentially macros which expand into -drive
options for various drive interfaces. The original forms bake in a lot
of assumptions from the days when QEMU was emulating a legacy PC, they
are not recommended for modern configurations.
-fda file
-fdb file
Use file as floppy disk 0/1 image (see the Disk Images <#disk-
images> chapter in the System Emulation Users Guide).
-hda file
-hdb file
-hdc file
-hdd file
Use file as hard disk 0, 1, 2 or 3 image on the default bus of
the emulated machine (this is for example the IDE bus on most
x86 machines, but it can also be SCSI, virtio or something else
on other target architectures). See also the Disk Images <#disk-
images> chapter in the System Emulation Users Guide.
-cdrom file
Use file as CD-ROM image on the default bus of the emulated
machine (which is IDE1 master on x86, so you cannot use -hdc and
-cdrom at the same time there). On systems that support it, you
can use the host CD-ROM by using /dev/cdrom as filename.
-blockdev option[,option[,option[,...]]]
Define a new block driver node. Some of the options apply to all
block drivers, other options are only accepted for a specific
block driver. See below for a list of generic options and
options for the most common block drivers.
Options that expect a reference to another node (e.g. file) can
be given in two ways. Either you specify the node name of an
already existing node (file=node-name), or you define a new node
inline, adding options for the referenced node after a dot
(file.filename=path,file.aio=native).
A block driver node created with -blockdev can be used for a
guest device by specifying its node name for the drive property
in a -device argument that defines a block device.
Valid options for any block driver node:
driver Specifies the block driver to use for the given
node.
node-name
This defines the name of the block driver node by
which it will be referenced later. The name must
be unique, i.e. it must not match the name of a
different block driver node, or (if you use -drive
as well) the ID of a drive.
If no node name is specified, it is automatically
generated. The generated node name is not
intended to be predictable and changes between
QEMU invocations. For the top level, an explicit
node name must be specified.
read-only
Open the node read-only. Guest write attempts will
fail.
Note that some block drivers support only
read-only access, either generally or in certain
configurations. In this case, the default value
read-only=off does not work and the option must be
specified explicitly.
auto-read-only
If auto-read-only=on is set, QEMU may fall back to
read-only usage even when read-only=off is
requested, or even switch between modes as needed,
e.g. depending on whether the image file is
writable or whether a writing user is attached to
the node.
force-share
Override the image locking system of QEMU by
forcing the node to utilize weaker shared access
for permissions where it would normally request
exclusive access. When there is the potential for
multiple instances to have the same file open
(whether this invocation of QEMU is the first or
the second instance), both instances must permit
shared access for the second instance to succeed
at opening the file.
Enabling force-share=on requires read-only=on.
cache.direct
The host page cache can be avoided with
cache.direct=on. This will attempt to do disk IO
directly to the guest's memory. QEMU may still
perform an internal copy of the data.
cache.no-flush
In case you don't care about data integrity over
host failures, you can use cache.no-flush=on. This
option tells QEMU that it never needs to write any
data to the disk but can instead keep things in
cache. If anything goes wrong, like your host
losing power, the disk storage getting
disconnected accidentally, etc. your image will
most probably be rendered unusable.
discard=discard
discard is one of "ignore" (or "off") or "unmap"
(or "on") and controls whether discard (also known
as trim or unmap) requests are ignored or passed
to the filesystem. Some machine types may not
support discard requests.
detect-zeroes=detect-zeroes
detect-zeroes is "off", "on" or "unmap" and
enables the automatic conversion of plain zero
writes by the OS to driver specific optimized zero
write commands. You may even choose "unmap" if
discard is set to "unmap" to allow a zero write to
be converted to an unmap operation.
Driver-specific options for file
This is the protocol-level block driver for accessing
regular files.
filename
The path to the image file in the local filesystem
aio Specifies the AIO backend
(threads/native/io_uring, default: threads)
locking
Specifies whether the image file is protected with
Linux OFD / POSIX locks. The default is to use the
Linux Open File Descriptor API if available,
otherwise no lock is applied. (auto/on/off,
default: auto)
Example:
-blockdev driver=file,node-name=disk,filename=disk.img
Driver-specific options for raw
This is the image format block driver for raw images. It
is usually stacked on top of a protocol level block
driver such as file.
file Reference to or definition of the data source
block driver node (e.g. a file driver node)
Example 1:
-blockdev driver=file,node-name=disk_file,filename=disk.img
-blockdev driver=raw,node-name=disk,file=disk_file
Example 2:
-blockdev driver=raw,node-name=disk,file.driver=file,file.filename=disk.img
Driver-specific options for qcow2
This is the image format block driver for qcow2 images.
It is usually stacked on top of a protocol level block
driver such as file.
file Reference to or definition of the data source
block driver node (e.g. a file driver node)
backing
Reference to or definition of the backing file
block device (default is taken from the image
file). It is allowed to pass null here in order to
disable the default backing file.
lazy-refcounts
Whether to enable the lazy refcounts feature
(on/off; default is taken from the image file)
cache-size
The maximum total size of the L2 table and
refcount block caches in bytes (default: the sum
of l2-cache-size and refcount-cache-size)
l2-cache-size
The maximum size of the L2 table cache in bytes
(default: if cache-size is not specified - 32M on
Linux platforms, and 8M on non-Linux platforms;
otherwise, as large as possible within the
cache-size, while permitting the requested or the
minimal refcount cache size)
refcount-cache-size
The maximum size of the refcount block cache in
bytes (default: 4 times the cluster size; or if
cache-size is specified, the part of it which is
not used for the L2 cache)
cache-clean-interval
Clean unused entries in the L2 and refcount
caches. The interval is in seconds. The default
value is 600 on supporting platforms, and 0 on
other platforms. Setting it to 0 disables this
feature.
pass-discard-request
Whether discard requests to the qcow2 device
should be forwarded to the data source (on/off;
default: on if discard=unmap is specified, off
otherwise)
pass-discard-snapshot
Whether discard requests for the data source
should be issued when a snapshot operation (e.g.
deleting a snapshot) frees clusters in the qcow2
file (on/off; default: on)
pass-discard-other
Whether discard requests for the data source
should be issued on other occasions where a
cluster gets freed (on/off; default: off)
discard-no-unref
When enabled, data clusters will remain
preallocated when they are no longer used, e.g.
because they are discarded or converted to zero
clusters. As usual, whether the old data is
discarded or kept on the protocol level (i.e. in
the image file) depends on the setting of the
pass-discard-request option. Keeping the clusters
preallocated prevents qcow2 fragmentation that
would otherwise be caused by freeing and
re-allocating them later. Besides potential
performance degradation, such fragmentation can
lead to increased allocation of clusters past the
end of the image file, resulting in image files
whose file length can grow much larger than their
guest disk size would suggest. If image file
length is of concern (e.g. when storing qcow2
images directly on block devices), you should
consider enabling this option.
overlap-check
Which overlap checks to perform for writes to the
image (none/constant/cached/all; default: cached).
For details or finer granularity control refer to
the QAPI documentation of blockdev-add.
Example 1:
-blockdev driver=file,node-name=my_file,filename=/tmp/disk.qcow2
-blockdev driver=qcow2,node-name=hda,file=my_file,overlap-check=none,cache-size=16777216
Example 2:
-blockdev driver=qcow2,node-name=disk,file.driver=http,file.filename=http://example.com/image.qcow2
Driver-specific options for other drivers
Please refer to the QAPI documentation of the
blockdev-add QMP command.
-drive option[,option[,option[,...]]]
Define a new drive. This includes creating a block driver node
(the backend) as well as a guest device, and is mostly a
shortcut for defining the corresponding -blockdev and -device
options.
-drive accepts all options that are accepted by -blockdev. In
addition, it knows the following options:
file=file
This option defines which disk image (see the Disk Images
<#disk-images> chapter in the System Emulation Users
Guide) to use with this drive. If the filename contains
comma, you must double it (for instance, "file=my,,file"
to use file "my,file").
Special files such as iSCSI devices can be specified
using protocol specific URLs. See the section for "Device
URL Syntax" for more information.
if=interface
This option defines on which type on interface the drive
is connected. Available types are: ide, scsi, sd, mtd,
floppy, pflash, virtio, none.
bus=bus,unit=unit
These options define where is connected the drive by
defining the bus number and the unit id.
index=index
This option defines where the drive is connected by using
an index in the list of available connectors of a given
interface type.
media=media
This option defines the type of the media: disk or cdrom.
snapshot=snapshot
snapshot is "on" or "off" and controls snapshot mode for
the given drive (see -snapshot).
cache=cache
cache is "none", "writeback", "unsafe", "directsync" or
"writethrough" and controls how the host cache is used to
access block data. This is a shortcut that sets the
cache.direct and cache.no-flush options (as in
-blockdev), and additionally cache.writeback, which
provides a default for the write-cache option of block
guest devices (as in -device). The modes correspond to
the following settings:
+-------------+-----------------+--------------+----------------+
| | cache.writeback | cache.direct | cache.no-flush |
+-------------+-----------------+--------------+----------------+
|writeback | on | off | off |
+-------------+-----------------+--------------+----------------+
|none | on | on | off |
+-------------+-----------------+--------------+----------------+
|writethrough | off | off | off |
+-------------+-----------------+--------------+----------------+
|directsync | off | on | off |
+-------------+-----------------+--------------+----------------+
|unsafe | on | off | on |
+-------------+-----------------+--------------+----------------+
The default mode is cache=writeback.
aio=aio
aio is "threads", "native", or "io_uring" and selects
between pthread based disk I/O, native Linux AIO, or
Linux io_uring API.
format=format
Specify which disk format will be used rather than
detecting the format. Can be used to specify format=raw
to avoid interpreting an untrusted format header.
werror=action,rerror=action
Specify which action to take on write and read errors.
Valid actions are: "ignore" (ignore the error and try to
continue), "stop" (pause QEMU), "report" (report the
error to the guest), "enospc" (pause QEMU only if the
host disk is full; report the error to the guest
otherwise). The default setting is werror=enospc and
rerror=report.
copy-on-read=copy-on-read
copy-on-read is "on" or "off" and enables whether to copy
read backing file sectors into the image file.
bps=b,bps_rd=r,bps_wr=w
Specify bandwidth throttling limits in bytes per second,
either for all request types or for reads or writes only.
Small values can lead to timeouts or hangs inside the
guest. A safe minimum for disks is 2 MiB/s.
bps_max=bm,bps_rd_max=rm,bps_wr_max=wm
Specify bursts in bytes per second, either for all
request types or for reads or writes only. Bursts allow
the guest I/O to spike above the limit temporarily.
iops=i,iops_rd=r,iops_wr=w
Specify request rate limits in requests per second,
either for all request types or for reads or writes only.
iops_max=bm,iops_rd_max=rm,iops_wr_max=wm
Specify bursts in requests per second, either for all
request types or for reads or writes only. Bursts allow
the guest I/O to spike above the limit temporarily.
iops_size=is
Let every is bytes of a request count as a new request
for iops throttling purposes. Use this option to prevent
guests from circumventing iops limits by sending fewer
but larger requests.
group=g
Join a throttling quota group with given name g. All
drives that are members of the same group are accounted
for together. Use this option to prevent guests from
circumventing throttling limits by using many small disks
instead of a single larger disk.
By default, the cache.writeback=on mode is used. It will report
data writes as completed as soon as the data is present in the
host page cache. This is safe as long as your guest OS makes
sure to correctly flush disk caches where needed. If your guest
OS does not handle volatile disk write caches correctly and your
host crashes or loses power, then the guest may experience data
corruption.
For such guests, you should consider using cache.writeback=off.
This means that the host page cache will be used to read and
write data, but write notification will be sent to the guest
only after QEMU has made sure to flush each write to the disk.
Be aware that this has a major impact on performance.
When using the -snapshot option, unsafe caching is always used.
Copy-on-read avoids accessing the same backing file sectors
repeatedly and is useful when the backing file is over a slow
network. By default copy-on-read is off.
Instead of -cdrom you can use:
qemu-system-x86_64 -drive file=file,index=2,media=cdrom
Instead of -hda, -hdb, -hdc, -hdd, you can use:
qemu-system-x86_64 -drive file=file,index=0,media=disk
qemu-system-x86_64 -drive file=file,index=1,media=disk
qemu-system-x86_64 -drive file=file,index=2,media=disk
qemu-system-x86_64 -drive file=file,index=3,media=disk
You can open an image using pre-opened file descriptors from an
fd set:
qemu-system-x86_64 \
-add-fd fd=3,set=2,opaque="rdwr:/path/to/file" \
-add-fd fd=4,set=2,opaque="rdonly:/path/to/file" \
-drive file=/dev/fdset/2,index=0,media=disk
You can connect a CDROM to the slave of ide0:
qemu-system-x86_64 -drive file=file,if=ide,index=1,media=cdrom
If you don't specify the "file=" argument, you define an empty
drive:
qemu-system-x86_64 -drive if=ide,index=1,media=cdrom
Instead of -fda, -fdb, you can use:
qemu-system-x86_64 -drive file=file,index=0,if=floppy
qemu-system-x86_64 -drive file=file,index=1,if=floppy
By default, interface is "ide" and index is automatically
incremented:
qemu-system-x86_64 -drive file=a -drive file=b
is interpreted like:
qemu-system-x86_64 -hda a -hdb b
-mtdblock file
Use file as on-board Flash memory image.
-sd file
Use file as SecureDigital card image.
-snapshot
Write to temporary files instead of disk image files. In this
case, the raw disk image you use is not written back. You can
however force the write back by pressing C-a s (see the Disk
Images <#disk-images> chapter in the System Emulation Users
Guide).
Warning:
snapshot is incompatible with -blockdev (instead use qemu-img
to manually create snapshot images to attach to your
blockdev). If you have mixed -blockdev and -drive
declarations you can use the 'snapshot' property on your
drive declarations instead of this global option.
-fsdev local,id=id,path=path,security_model=security_model
[,writeout=writeout][,readonly=on][,fmode=fmode][,dmode=dmode]
[,throttling.option=value[,throttling.option=value[,...]]]
-fsdev synth,id=id[,readonly=on]
Define a new file system device. Valid options are:
local Accesses to the filesystem are done by QEMU.
synth Synthetic filesystem, only used by QTests.
id=id Specifies identifier for this device.
path=path
Specifies the export path for the file system device.
Files under this path will be available to the 9p client
on the guest.
security_model=security_model
Specifies the security model to be used for this export
path. Supported security models are "passthrough",
"mapped-xattr", "mapped-file" and "none". In
"passthrough" security model, files are stored using the
same credentials as they are created on the guest. This
requires QEMU to run as root. In "mapped-xattr" security
model, some of the file attributes like uid, gid, mode
bits and link target are stored as file attributes. For
"mapped-file" these attributes are stored in the hidden
.virtfs_metadata directory. Directories exported by this
security model cannot interact with other unix tools.
"none" security model is same as passthrough except the
sever won't report failures if it fails to set file
attributes like ownership. Security model is mandatory
only for local fsdriver.
writeout=writeout
This is an optional argument. The only supported value is
"immediate". This means that host page cache will be used
to read and write data but write notification will be
sent to the guest only when the data has been reported as
written by the storage subsystem.
readonly=on
Enables exporting 9p share as a readonly mount for
guests. By default read-write access is given.
fmode=fmode
Specifies the default mode for newly created files on the
host. Works only with security models "mapped-xattr" and
"mapped-file".
dmode=dmode
Specifies the default mode for newly created directories
on the host. Works only with security models
"mapped-xattr" and "mapped-file".
throttling.bps-total=b,throttling.bps-read=r,throttling.bps-write=w
Specify bandwidth throttling limits in bytes per second,
either for all request types or for reads or writes only.
throttling.bps-total-max=bm,bps-read-max=rm,bps-write-max=wm
Specify bursts in bytes per second, either for all
request types or for reads or writes only. Bursts allow
the guest I/O to spike above the limit temporarily.
throttling.iops-total=i,throttling.iops-read=r,
throttling.iops-write=w
Specify request rate limits in requests per second,
either for all request types or for reads or writes only.
throttling.iops-total-max=im,throttling.iops-read-max=irm,
throttling.iops-write-max=iwm
Specify bursts in requests per second, either for all
request types or for reads or writes only. Bursts allow
the guest I/O to spike above the limit temporarily.
throttling.iops-size=is
Let every is bytes of a request count as a new request
for iops throttling purposes.
-fsdev option is used along with -device driver "virtio-9p-...".
-device virtio-9p-type,fsdev=id,mount_tag=mount_tag
Options for virtio-9p-... driver are:
type Specifies the variant to be used. Supported values are
"pci", "ccw" or "device", depending on the machine type.
fsdev=id
Specifies the id value specified along with -fsdev
option.
mount_tag=mount_tag
Specifies the tag name to be used by the guest to mount
this export point.
-virtfs local,path=path,mount_tag=mount_tag
,security_model=security_model[,writeout=writeout][,readonly=on]
[,fmode=fmode][,dmode=dmode][,multidevs=multidevs]
-virtfs synth,mount_tag=mount_tag
Define a new virtual filesystem device and expose it to the
guest using a virtio-9p-device (a.k.a. 9pfs), which essentially
means that a certain directory on host is made directly
accessible by guest as a pass-through file system by using the
9P network protocol for communication between host and guests,
if desired even accessible, shared by several guests
simultaneously.
Note that -virtfs is actually just a convenience shortcut for
its generalized form -fsdev -device virtio-9p-pci.
The general form of pass-through file system options are:
local Accesses to the filesystem are done by QEMU.
synth Synthetic filesystem, only used by QTests.
id=id Specifies identifier for the filesystem device
path=path
Specifies the export path for the file system device.
Files under this path will be available to the 9p client
on the guest.
security_model=security_model
Specifies the security model to be used for this export
path. Supported security models are "passthrough",
"mapped-xattr", "mapped-file" and "none". In
"passthrough" security model, files are stored using the
same credentials as they are created on the guest. This
requires QEMU to run as root. In "mapped-xattr" security
model, some of the file attributes like uid, gid, mode
bits and link target are stored as file attributes. For
"mapped-file" these attributes are stored in the hidden
.virtfs_metadata directory. Directories exported by this
security model cannot interact with other unix tools.
"none" security model is same as passthrough except the
sever won't report failures if it fails to set file
attributes like ownership. Security model is mandatory
only for local fsdriver.
writeout=writeout
This is an optional argument. The only supported value is
"immediate". This means that host page cache will be used
to read and write data but write notification will be
sent to the guest only when the data has been reported as
written by the storage subsystem.
readonly=on
Enables exporting 9p share as a readonly mount for
guests. By default read-write access is given.
fmode=fmode
Specifies the default mode for newly created files on the
host. Works only with security models "mapped-xattr" and
"mapped-file".
dmode=dmode
Specifies the default mode for newly created directories
on the host. Works only with security models
"mapped-xattr" and "mapped-file".
mount_tag=mount_tag
Specifies the tag name to be used by the guest to mount
this export point.
multidevs=remap|forbid|warn
Specifies how to deal with multiple devices being shared
with the same 9p export in order to avoid file ID
collisions on guest. Supported behaviours are either
"remap" (default), "forbid" or "warn".
remap : assumes the possibility that more than one device
is shared with the same 9p export. Therefore inode
numbers from host are remapped for guest in a way that
would prevent file ID collisions on guest. Remapping
inodes in such cases is required because the original
device IDs from host are never passed and exposed on
guest. Instead all files of an export shared with virtfs
always share the same device ID on guest. So two files
with identical inode numbers but from actually different
devices on host would otherwise cause a file ID collision
and hence potential severe misbehaviours on guest.
warn : virtfs 9p expects only one device to be shared
with the same export. If however more than one device is
shared and accessed via the same 9p export then only a
warning message is logged (once) by qemu on host side. No
further action is performed in this case that would
prevent file ID collisions on guest. This could thus lead
to severe misbehaviours in this case like wrong files
being accessed and data corruption on the exported tree.
forbid : assumes like "warn" that only one device is
shared by the same 9p export, however it will not only
log a warning message but also deny access to additional
devices on guest. Note though that "forbid" does
currently not block all possible file access operations
(e.g. readdir() would still return entries from other
devices).
-iscsi Configure iSCSI session parameters.
USB convenience options
-usb Enable USB emulation on machine types with an on-board USB host
controller (if not enabled by default). Note that on-board USB
host controllers may not support USB 3.0. In this case -device
qemu-xhci can be used instead on machines with PCI.
-usbdevice devname
Add the USB device devname, and enable an on-board USB
controller if possible and necessary (just like it can be done
via -machine usb=on). Note that this option is mainly intended
for the user's convenience only. More fine-grained control can
be achieved by selecting a USB host controller (if necessary)
and the desired USB device via the -device option instead. For
example, instead of using -usbdevice mouse it is possible to use
-device qemu-xhci -device usb-mouse to connect the USB mouse to
a USB 3.0 controller instead (at least on machines that support
PCI and do not have an USB controller enabled by default yet).
For more details, see the chapter about Connecting USB devices
<#connecting-usb-devices> in the System Emulation Users Guide.
Possible devices for devname are:
braille
Braille device. This will use BrlAPI to display the
braille output on a real or fake device (i.e. it also
creates a corresponding braille chardev automatically
beside the usb-braille USB device).
keyboard
Standard USB keyboard. Will override the PS/2 keyboard
(if present).
mouse Virtual Mouse. This will override the PS/2 mouse
emulation when activated.
tablet Pointer device that uses absolute coordinates (like a
touchscreen). This means QEMU is able to report the mouse
position without having to grab the mouse. Also overrides
the PS/2 mouse emulation when activated.
wacom-tablet
Wacom PenPartner USB tablet.
Display options
-display type
Select type of display to use. This may also influence the
default audio backend selection.
Use -display help to list the available display types. Valid
values for type are
spice-app[,gl=on|off]
Start QEMU as a Spice server and launch the default Spice
client application. The Spice server will redirect the
serial consoles and QEMU monitors. (Since 4.0)
dbus Export the display over D-Bus interfaces. (Since 7.0)
If no audio backend is specified and the dbus display
backend is specified, the dbus audio backend is used by
default.
The connection is registered with the "org.qemu" name
(and queued when already owned).
addr= : D-Bus bus address to connect to.
p2p=yes|no : Use peer-to-peer connection, accepted via
QMP add_client.
gl=on|off|core|es : Use OpenGL for rendering (the D-Bus
interface will share framebuffers with DMABUF file
descriptors).
sdl Display video output via SDL (usually in a separate
graphics window; see the SDL documentation for other
possibilities). Valid parameters are:
grab-mod= : Used to select the modifier keys for
toggling the mouse grabbing in conjunction with the "g"
key. can be either lshift-lctrl-lalt or rctrl.
gl=on|off|core|es : Use OpenGL for displaying
show-cursor=on|off : Force showing the mouse cursor
window-close=on|off : Allow to quit qemu with window
close button
gtk Display video output in a GTK window. This interface
provides drop-down menus and other UI elements to
configure and control the VM during runtime. Valid
parameters are:
full-screen=on|off : Start in fullscreen mode
gl=on|off : Use OpenGL for displaying
grab-on-hover=on|off : Grab keyboard input on mouse hover
show-tabs=on|off (Display the tab bar for switching
between the)
various graphical interfaces (e.g. VGA and virtual
console character devices) by default.
show-cursor=on|off : Force showing the mouse cursor
window-close=on|off : Allow to quit qemu with window
close button
show-menubar=on|off : Display the main window menubar,
defaults to "on"
zoom-to-fit=on|off (Expand video output to the window
size,) defaults to "off"
curses[,charset=]
Display video output via curses. For graphics device
models which support a text mode, QEMU can display this
output using a curses/ncurses interface. Nothing is
displayed when the graphics device is in graphical mode
or if the graphics device does not support a text mode.
Generally only the VGA device models support text mode.
The font charset used by the guest can be specified with
the charset option, for example charset=CP850 for IBM
CP850 encoding. The default is CP437.
cocoa Display video output in a Cocoa window. Mac only. This
interface provides drop-down menus and other UI elements
to configure and control the VM during runtime. Valid
parameters are:
full-grab=on|off (Capture all key presses, including
system combos.)
This requires accessibility permissions, since it
performs a global grab on key events. (default:
off) See
swap-opt-cmd=on|off (Swap the Option and Command keys so
that their)
key codes match their position on non-Mac
keyboards and you can use Meta/Super and Alt where
you expect them. (default: off)
show-cursor=on|off : Force showing the mouse cursor
left-command-key=on|off : Disable forwarding left command
key to host
full-screen=on|off : Start in fullscreen mode
zoom-to-fit=on|off (Expand video output to the window
size,) defaults to "off"
egl-headless[,rendernode=]
Offload all OpenGL operations to a local DRI device. For
any graphical display, this display needs to be paired
with either VNC or SPICE displays.
vnc=
Start a VNC server on display
none Do not display video output. The guest will still see an
emulated graphics card, but its output will not be
displayed to the QEMU user. This option differs from the
-nographic option in that it only affects what is done
with video output; -nographic also changes the
destination of the serial and parallel port data.
-nographic
Normally, if QEMU is compiled with graphical window support, it
displays output such as guest graphics, guest console, and the
QEMU monitor in a window. With this option, you can totally
disable graphical output so that QEMU is a simple command line
application. The emulated serial port is redirected on the
console and muxed with the monitor (unless redirected elsewhere
explicitly). Therefore, you can still use QEMU to debug a Linux
kernel with a serial console. Use C-a h for help on switching
between the console and monitor.
-spice option[,option[,...]]
Enable the spice remote desktop protocol. Valid options are
port=
Set the TCP port spice is listening on for plaintext
channels.
addr=
Set the IP address spice is listening on. Default is any
address.
ipv4=on|off; ipv6=on|off; unix=on|off
Force using the specified IP version.
password-secret=
Set the ID of the secret object containing the password
you need to authenticate.
sasl=on|off
Require that the client use SASL to authenticate with the
spice. The exact choice of authentication method used is
controlled from the system / user's SASL configuration
file for the 'qemu' service. This is typically found in
/etc/sasl2/qemu.conf. If running QEMU as an unprivileged
user, an environment variable SASL_CONF_PATH can be used
to make it search alternate locations for the service
config. While some SASL auth methods can also provide
data encryption (eg GSSAPI), it is recommended that SASL
always be combined with the 'tls' and 'x509' settings to
enable use of SSL and server certificates. This ensures a
data encryption preventing compromise of authentication
credentials.
disable-ticketing=on|off
Allow client connects without authentication.
disable-copy-paste=on|off
Disable copy paste between the client and the guest.
disable-agent-file-xfer=on|off
Disable spice-vdagent based file-xfer between the client
and the guest.
tls-port=
Set the TCP port spice is listening on for encrypted
channels.
x509-dir=
Set the x509 file directory. Expects same filenames as
-vnc $display,x509=$dir
x509-key-file=; x509-key-password=;
x509-cert-file=; x509-cacert-file=;
x509-dh-key-file=
The x509 file names can also be configured individually.
tls-ciphers=
Specify which ciphers to use.
tls-channel=main|display|cursor|inputs|record|playback;
plaintext-channel=main|display|cursor|inputs|record|playback
Force specific channel to be used with or without TLS
encryption. The options can be specified multiple times
to configure multiple channels. The special name
"default" can be used to set the default mode. For
channels which are not explicitly forced into one mode
the spice client is allowed to pick tls/plaintext as he
pleases.
image-compression=auto_glz|auto_lz|quic|glz|lz|off
Configure image compression (lossless). Default is
auto_glz.
jpeg-wan-compression=auto|never|always;
zlib-glz-wan-compression=auto|never|always
Configure wan image compression (lossy for slow links).
Default is auto.
streaming-video=off|all|filter
Configure video stream detection. Default is off.
agent-mouse=on|off
Enable/disable passing mouse events via vdagent. Default
is on.
playback-compression=on|off
Enable/disable audio stream compression (using celt
0.5.1). Default is on.
seamless-migration=on|off
Enable/disable spice seamless migration. Default is off.
video-codec=
Provide the preferred codec the Spice server should use
with the Gstreamer encoder. This option is only relevant
when gl=on is specified. If no codec is provided, then
the codec gstreamer:h264 would be used as default. And,
for the case where gl=off, the default codec to be used
is determined by the Spice server.
max-refresh-rate=rate
Provide the maximum refresh rate (or FPS) at which the
encoding requests should be sent to the Spice server.
Default would be 30.
gl=on|off
Enable/disable OpenGL context. Default is off.
rendernode=
DRM render node for OpenGL rendering. If not specified,
it will pick the first available. (Since 2.9)
-vga type
Select type of VGA card to emulate. Valid values for type are
cirrus Cirrus Logic GD5446 Video card. All Windows versions
starting from Windows 95 should recognize and use this
graphic card. For optimal performances, use 16 bit color
depth in the guest and the host OS. (This card was the
default before QEMU 2.2)
std Standard VGA card with Bochs VBE extensions. If your
guest OS supports the VESA 2.0 VBE extensions (e.g.
Windows XP) and if you want to use high resolution modes
(>= 1280x1024x16) then you should use this option. (This
card is the default since QEMU 2.2)
vmware VMWare SVGA-II compatible adapter. Use it if you have
sufficiently recent XFree86/XOrg server or Windows guest
with a driver for this card.
qxl QXL paravirtual graphic card. It is VGA compatible
(including VESA 2.0 VBE support). Works best with qxl
guest drivers installed though. Recommended choice when
using the spice protocol.
tcx (sun4m only) Sun TCX framebuffer. This is the default
framebuffer for sun4m machines and offers both 8-bit and
24-bit colour depths at a fixed resolution of 1024x768.
cg3 (sun4m only) Sun cgthree framebuffer. This is a simple
8-bit framebuffer for sun4m machines available in both
1024x768 (OpenBIOS) and 1152x900 (OBP) resolutions aimed
at people wishing to run older Solaris versions.
virtio Virtio VGA card.
none Disable VGA card.
-full-screen
Start in full screen.
-g widthxheight[xdepth]
Set the initial graphical resolution and depth (PPC, SPARC
only).
For PPC the default is 800x600x32.
For SPARC with the TCX graphics device, the default is
1024x768x8 with the option of 1024x768x24. For cgthree, the
default is 1024x768x8 with the option of 1152x900x8 for people
who wish to use OBP.
-vnc display[,option[,option[,...]]]
Normally, if QEMU is compiled with graphical window support, it
displays output such as guest graphics, guest console, and the
QEMU monitor in a window. With this option, you can have QEMU
listen on VNC display display and redirect the VGA display over
the VNC session. It is very useful to enable the usb tablet
device when using this option (option -device usb-tablet). When
using the VNC display, you must use the -k parameter to set the
keyboard layout if you are not using en-us. Valid syntax for the
display is
to=L With this option, QEMU will try next available VNC
displays, until the number L, if the originally defined
"-vnc display" is not available, e.g. port 5900+display
is already used by another application. By default, to=0.
host:d TCP connections will only be allowed from host on display
d. By convention the TCP port is 5900+d. Optionally, host
can be omitted in which case the server will accept
connections from any host.
unix:path
Connections will be allowed over UNIX domain sockets
where path is the location of a unix socket to listen for
connections on.
none VNC is initialized but not started. The monitor change
command can be used to later start the VNC server.
Following the display value there may be one or more option
flags separated by commas. Valid options are
reverse=on|off
Connect to a listening VNC client via a "reverse"
connection. The client is specified by the display. For
reverse network connections (host:d,``reverse``), the d
argument is a TCP port number, not a display number.
websocket=on|off
Opens an additional TCP listening port dedicated to VNC
Websocket connections. If a bare websocket option is
given, the Websocket port is 5700+display. An alternative
port can be specified with the syntax websocket=port.
If host is specified connections will only be allowed
from this host. It is possible to control the websocket
listen address independently, using the syntax
websocket=host:port.
Websocket could be allowed over UNIX domain socket, using
the syntax websocket=unix:path, where path is the
location of a unix socket to listen for connections on.
If no TLS credentials are provided, the websocket
connection runs in unencrypted mode. If TLS credentials
are provided, the websocket connection requires encrypted
client connections.
password=on|off
Require that password based authentication is used for
client connections.
The password must be set separately using the
set_password command in the QEMU Monitor <#qemu-monitor>.
The syntax to change your password is: set_password
where could be either
"vnc" or "spice".
If you would like to change password
expiration, you should use expire_password
where expiration time could be one of
the following options: now, never, +seconds or UNIX time
of expiration, e.g. +60 to make password expire in 60
seconds, or 1335196800 to make password expire on "Mon
Apr 23 12:00:00 EDT 2012" (UNIX time for this date and
time).
You can also use keywords "now" or "never" for the
expiration time to allow password to expire
immediately or never expire.
password-secret=
Require that password based authentication is used for
client connections, using the password provided by the
secret object identified by secret-id.
tls-creds=ID
Provides the ID of a set of TLS credentials to use to
secure the VNC server. They will apply to both the normal
VNC server socket and the websocket socket (if enabled).
Setting TLS credentials will cause the VNC server socket
to enable the VeNCrypt auth mechanism. The credentials
should have been previously created using the -object
tls-creds argument.
tls-authz=ID
Provides the ID of the QAuthZ authorization object
against which the client's x509 distinguished name will
validated. This object is only resolved at time of use,
so can be deleted and recreated on the fly while the VNC
server is active. If missing, it will default to denying
access.
sasl=on|off
Require that the client use SASL to authenticate with the
VNC server. The exact choice of authentication method
used is controlled from the system / user's SASL
configuration file for the 'qemu' service. This is
typically found in /etc/sasl2/qemu.conf. If running QEMU
as an unprivileged user, an environment variable
SASL_CONF_PATH can be used to make it search alternate
locations for the service config. While some SASL auth
methods can also provide data encryption (eg GSSAPI), it
is recommended that SASL always be combined with the
'tls' and 'x509' settings to enable use of SSL and server
certificates. This ensures a data encryption preventing
compromise of authentication credentials. See the VNC
security <#vnc-security> section in the System Emulation
Users Guide for details on using SASL authentication.
sasl-authz=ID
Provides the ID of the QAuthZ authorization object
against which the client's SASL username will validated.
This object is only resolved at time of use, so can be
deleted and recreated on the fly while the VNC server is
active. If missing, it will default to denying access.
acl=on|off
Legacy method for enabling authorization of clients
against the x509 distinguished name and SASL username. It
results in the creation of two authz-list objects with
IDs of vnc.username and vnc.x509dname. The rules for
these objects must be configured with the HMP ACL
commands.
This option is deprecated and should no longer be used.
The new sasl-authz and tls-authz options are a
replacement.
lossy=on|off
Enable lossy compression methods (gradient, JPEG, ...).
If this option is set, VNC client may receive lossy
framebuffer updates depending on its encoding settings.
Enabling this option can save a lot of bandwidth at the
expense of quality.
non-adaptive=on|off
Disable adaptive encodings. Adaptive encodings are
enabled by default. An adaptive encoding will try to
detect frequently updated screen regions, and send
updates in these regions using a lossy encoding (like
JPEG). This can be really helpful to save bandwidth when
playing videos. Disabling adaptive encodings restores the
original static behavior of encodings like Tight.
share=allow-exclusive|force-shared|ignore
Set display sharing policy. 'allow-exclusive' allows
clients to ask for exclusive access. As suggested by the
rfb spec this is implemented by dropping other
connections. Connecting multiple clients in parallel
requires all clients asking for a shared session
(vncviewer: -shared switch). This is the default.
'force-shared' disables exclusive client access. Useful
for shared desktop sessions, where you don't want someone
forgetting specify -shared disconnect everybody else.
'ignore' completely ignores the shared flag and allows
everybody connect unconditionally. Doesn't conform to the
rfb spec but is traditional QEMU behavior.
key-delay-ms
Set keyboard delay, for key down and key up events, in
milliseconds. Default is 10. Keyboards are low-bandwidth
devices, so this slowdown can help the device and guest
to keep up and not lose events in case events are
arriving in bulk. Possible causes for the latter are
flaky network connections, or scripts for automated
testing.
audiodev=audiodev
Use the specified audiodev when the VNC client requests
audio transmission. When not using an -audiodev argument,
this option must be omitted, otherwise is must be present
and specify a valid audiodev.
power-control=on|off
Permit the remote client to issue shutdown, reboot or
reset power control requests.
i386 target only
-win2k-hack
Use it when installing Windows 2000 to avoid a disk full bug.
After Windows 2000 is installed, you no longer need this option
(this option slows down the IDE transfers). Synonym of -global
ide-device.win2k-install-hack=on.
-no-fd-bootchk
Disable boot signature checking for floppy disks in BIOS. May be
needed to boot from old floppy disks. Synonym of -m
fd-bootchk=off.
-acpitable
[sig=str][,rev=n][,oem_id=str][,oem_table_id=str][,oem_rev=n]
[,asl_compiler_id=str][,asl_compiler_rev=n][,data=file1[:file2]...]
Add ACPI table with specified header fields and context from
specified files. For file=, take whole ACPI table from the
specified files, including all ACPI headers (possible overridden
by other options). For data=, only data portion of the table is
used, all header information is specified in the command line.
If a SLIC table is supplied to QEMU, then the SLIC's oem_id and
oem_table_id fields will override the same in the RSDT and the
FADT (a.k.a. FACP), in order to ensure the field matches
required by the Microsoft SLIC spec and the ACPI spec.
-smbios file=binary
Load SMBIOS entry from binary file.
-smbios
type=0[,vendor=str][,version=str][,date=str][,release=%d.%d][,uefi=on|off]
Specify SMBIOS type 0 fields
-smbios
type=1[,manufacturer=str][,product=str][,version=str][,serial=str][,uuid=uuid][,sku=str][,family=str]
Specify SMBIOS type 1 fields
-smbios
type=2[,manufacturer=str][,product=str][,version=str][,serial=str][,asset=str][,location=str]
Specify SMBIOS type 2 fields
-smbios
type=3[,manufacturer=str][,version=str][,serial=str][,asset=str][,sku=str]
Specify SMBIOS type 3 fields
-smbios
type=4[,sock_pfx=str][,manufacturer=str][,version=str][,serial=str][,asset=str][,part=str][,processor-family=%d][,processor-id=%d]
Specify SMBIOS type 4 fields
-smbios
type=9[,slot_designation=str][,slot_type=%d][,slot_data_bus_width=%d][,current_usage=%d][,slot_length=%d][,slot_id=%d][,slot_characteristics1=%d][,slot_characteristics12=%d][,pci_device=str]
Specify SMBIOS type 9 fields
-smbios type=11[,value=str][,path=filename]
Specify SMBIOS type 11 fields
This argument can be repeated multiple times, and values are
added in the order they are parsed. Applications intending to
use OEM strings data are encouraged to use their application
name as a prefix for the value string. This facilitates passing
information for multiple applications concurrently.
The value=str syntax provides the string data inline, while the
path=filename syntax loads data from a file on disk. Note that
the file is not permitted to contain any NUL bytes.
Both the value and path options can be repeated multiple times
and will be added to the SMBIOS table in the order in which they
appear.
Note that on the x86 architecture, the total size of all SMBIOS
tables is limited to 65535 bytes. Thus the OEM strings data is
not suitable for passing large amounts of data into the guest.
Instead it should be used as a indicator to inform the guest
where to locate the real data set, for example, by specifying
the serial ID of a block device.
An example passing three strings is
-smbios type=11,value=cloud-init:ds=nocloud-net;s=http://10.10.0.1:8000/,\
value=anaconda:method=http://dl.fedoraproject.org/pub/fedora/linux/releases/25/x86_64/os,\
path=/some/file/with/oemstringsdata.txt
In the guest OS this is visible with the dmidecode command
$ dmidecode -t 11
Handle 0x0E00, DMI type 11, 5 bytes
OEM Strings
String 1: cloud-init:ds=nocloud-net;s=http://10.10.0.1:8000/
String 2: anaconda:method=http://dl.fedoraproject.org/pub/fedora/linux/releases/25/x86_64/os
String 3: myapp:some extra data
-smbios
type=17[,loc_pfx=str][,bank=str][,manufacturer=str][,serial=str][,asset=str][,part=str][,speed=%d]
Specify SMBIOS type 17 fields
-smbios type=41[,designation=str][,kind=str][,instance=%d][,pcidev=str]
Specify SMBIOS type 41 fields
This argument can be repeated multiple times. Its main use is
to allow network interfaces be created as enoX on Linux, with X
being the instance number, instead of the name depending on the
interface position on the PCI bus.
Here is an example of use:
-netdev user,id=internet \
-device virtio-net-pci,mac=50:54:00:00:00:42,netdev=internet,id=internet-dev \
-smbios type=41,designation='Onboard LAN',instance=1,kind=ethernet,pcidev=internet-dev
In the guest OS, the device should then appear as eno1:
..parsed-literal:
$ ip -brief l
lo UNKNOWN 00:00:00:00:00:00
eno1 UP 50:54:00:00:00:42
Currently, the PCI device has to be attached to the root bus.
Network options
-nic
[tap|passt|bridge|user|l2tpv3|vde|netmap|af-xdp|vhost-user|socket][,...][,mac=macaddr][,model=mn]
This option is a shortcut for configuring both the on-board
(default) guest NIC hardware and the host network backend in one
go. The host backend options are the same as with the
corresponding -netdev options below. The guest NIC model can be
set with model=modelname. Use model=help to list the available
device types. The hardware MAC address can be set with
mac=macaddr.
The following two example do exactly the same, to show how -nic
can be used to shorten the command line length:
qemu-system-x86_64 -netdev user,id=n1,ipv6=off -device e1000,netdev=n1,mac=52:54:98:76:54:32
qemu-system-x86_64 -nic user,ipv6=off,model=e1000,mac=52:54:98:76:54:32
-nic none
Indicate that no network devices should be configured. It is
used to override the default configuration (default NIC with
"user" host network backend) which is activated if no other
networking options are provided.
-netdev passt,id=str[,option][,...]
Configure a passt network backend which requires no
administrator privilege to run. Valid options are:
id=id Assign symbolic name for use in monitor commands.
path=file
Filename of the passt program to run. If it is not
provided, passt command will be started with the help of
the PATH environment variable.
quiet=on|off
By default, quiet=on to disable informational message
from passt. quiet=on is passed as --quiet to passt.
vhost-user=on|off
By default, vhost-user=off and QEMU uses the stream
network backend to communicate with passt. If
vhost-user=on, passt is started with --vhost-user and
QEMU uses the vhost-user network backend to communicate
with passt.
@mtu Assign MTU via DHCP/NDP
address
IPv4 or IPv6 address
netmask
IPv4 mask
mac source MAC address
gateway
IPv4 or IPv6 address as gateway
interface
Interface for addresses and routes
outbound
Bind to address as outbound source
outbound-if4
Bind to outbound interface for IPv4
outbound-if6
Bind to outbound interface for IPv6
dns IPv4 or IPv6 address as DNS
search Search domains
fqdn FQDN to configure client with
dhcp-dns
Enable/disable DNS list in DHCP/DHCPv6/NDP
dhcp-search
Enable/disable list in DHCP/DHCPv6/NDP
map-host-loopback
Address to refer to host
map-guest-addr
Addr to translate to guest's address
dns-forward
Forward DNS queries sent to
dns-host
Host nameserver to direct queries to
tcp Enable/disable TCP
udp Enable/disable UDP
icmp Enable/disable ICMP
dhcp Enable/disable DHCP
ndp Enable/disable NDP
dhcpv6 Enable/disable DHCPv6
ra Enable/disable route advertisements
freebind
Bind to any address for forwarding
ipv4 Enable/disable IPv4
ipv6 Enable/disable IPv6
tcp-ports
TCP ports to forward
udp-ports
UDP ports to forward
param=string
string will be passed to passt as a command line
parameter, we can have multiple occurrences of the param
parameter to pass multiple parameters to passt.
For instance, to pass --trace --log=trace.log:
qemu-system-x86_64 -nic passt,param=--trace,param=--log=trace.log
-netdev user,id=id[,option][,option][,...]
Configure user mode host network backend which requires no
administrator privilege to run. Valid options are:
id=id Assign symbolic name for use in monitor commands.
ipv4=on|off and ipv6=on|off
Specify that either IPv4 or IPv6 must be enabled. If
neither is specified both protocols are enabled.
net=addr[/mask]
Set IP network address the guest will see. Optionally
specify the netmask, either in the form a.b.c.d or as
number of valid top-most bits. Default is 10.0.2.0/24.
host=addr
Specify the guest-visible address of the host. Default is
the 2nd IP in the guest network, i.e. x.x.x.2.
ipv6-net=addr[/int]
Set IPv6 network address the guest will see (default is
fec0::/64). The network prefix is given in the usual
hexadecimal IPv6 address notation. The prefix size is
optional, and is given as the number of valid top-most
bits (default is 64).
ipv6-host=addr
Specify the guest-visible IPv6 address of the host.
Default is the 2nd IPv6 in the guest network, i.e.
xxxx::2.
restrict=on|off
If this option is enabled, the guest will be isolated,
i.e. it will not be able to contact the host and no guest
IP packets will be routed over the host to the outside.
This option does not affect any explicitly set forwarding
rules.
hostname=name
Specifies the client hostname reported by the built-in
DHCP server.
dhcpstart=addr
Specify the first of the 16 IPs the built-in DHCP server
can assign. Default is the 15th to 31st IP in the guest
network, i.e. x.x.x.15 to x.x.x.31.
dns=addr
Specify the guest-visible address of the virtual
nameserver. The address must be different from the host
address. Default is the 3rd IP in the guest network, i.e.
x.x.x.3.
ipv6-dns=addr
Specify the guest-visible address of the IPv6 virtual
nameserver. The address must be different from the host
address. Default is the 3rd IP in the guest network,
i.e. xxxx::3.
dnssearch=domain
Provides an entry for the domain-search list sent by the
built-in DHCP server. More than one domain suffix can be
transmitted by specifying this option multiple times. If
supported, this will cause the guest to automatically try
to append the given domain suffix(es) in case a domain
name can not be resolved.
Example:
qemu-system-x86_64 -nic user,dnssearch=mgmt.example.org,dnssearch=example.org
domainname=domain
Specifies the client domain name reported by the built-in
DHCP server.
tftp=dir
When using the user mode network stack, activate a
built-in TFTP server. The files in dir will be exposed as
the root of a TFTP server. The TFTP client on the guest
must be configured in binary mode (use the command bin of
the Unix TFTP client). The built-in TFTP server is
read-only; it does not implement any command for writing
files. QEMU will not write to this directory.
tftp-server-name=name
In BOOTP reply, broadcast name as the "TFTP server name"
(RFC2132 option 66). This can be used to advise the guest
to load boot files or configurations from a different
server than the host address.
bootfile=file
When using the user mode network stack, broadcast file as
the BOOTP filename. In conjunction with tftp, this can be
used to network boot a guest from a local directory.
Example (using pxelinux):
qemu-system-x86_64 -hda linux.img -boot n -device e1000,netdev=n1 \
-netdev user,id=n1,tftp=/path/to/tftp/files,bootfile=/pxelinux.0
smb=dir[,smbserver=addr]
When using the user mode network stack, activate a
built-in SMB server so that Windows OSes can access to
the host files in dir transparently. The IP address of
the SMB server can be set to addr. By default the 4th IP
in the guest network is used, i.e. x.x.x.4.
In the guest Windows OS, the line:
10.0.2.4 smbserver
must be added in the file C:\WINDOWS\LMHOSTS (for windows
9x/Me) or C:\WINNT\SYSTEM32\DRIVERS\ETC\LMHOSTS (Windows
NT/2000).
Then dir can be accessed in \\smbserver\qemu.
Note that a SAMBA server must be installed on the host
OS.
hostfwd=[tcp|udp|unix]:[[hostaddr]:hostport|hostpath]-[guestaddr]:guestport
Redirect incoming TCP, UDP or UNIX connections to the
host port hostport to the guest IP address guestaddr on
guest port guestport. If guestaddr is not specified, its
value is x.x.x.15 (default first address given by the
built-in DHCP server). By specifying hostaddr, the rule
can be bound to a specific host interface. If no
connection type is set, TCP is used. This option can be
given multiple times.
For example, to redirect host X11 connection from screen
1 to guest screen 0, use the following:
# on the host
qemu-system-x86_64 -nic user,hostfwd=tcp:127.0.0.1:6001-:6000
# this host xterm should open in the guest X11 server
xterm -display :1
To redirect telnet connections from host port 5555 to
telnet port on the guest, use the following:
# on the host
qemu-system-x86_64 -nic user,hostfwd=tcp::5555-:23
telnet localhost 5555
Then when you use on the host telnet localhost 5555, you
connect to the guest telnet server.
To redirect host unix socket /tmp/vm to guest tcp socket
23 use following:
# on the host
qemu-system-x86_64 -nic user,hostfwd=unix:/tmp/vm-:23
guestfwd=[tcp]:server:port-dev;
guestfwd=[tcp]:server:port-cmd:command
Forward guest TCP connections to the IP address server on
port port to the character device dev or to a program
executed by cmd:command which gets spawned for each
connection. This option can be given multiple times.
You can either use a chardev directly and have that one
used throughout QEMU's lifetime, like in the following
example:
# open 10.10.1.1:4321 on bootup, connect 10.0.2.100:1234 to it whenever
# the guest accesses it
qemu-system-x86_64 -nic user,guestfwd=tcp:10.0.2.100:1234-
Or you can execute a command on every TCP connection
established by the guest, so that QEMU behaves similar to
an inetd process for that virtual server:
# call "netcat 10.10.1.1 4321" on every TCP connection to 10.0.2.100:1234
# and connect the TCP stream to its stdin/stdout
qemu-system-x86_64 -nic 'user,id=n1,guestfwd=tcp:10.0.2.100:1234-cmd:netcat 10.10.1.1 4321'
-netdev
tap,id=id[,fd=h][,ifname=name][,script=file][,downscript=dfile][,br=bridge][,helper=helper]
Configure a host TAP network backend with ID id.
Use the network script file to configure it and the network
script dfile to deconfigure it. If name is not provided, the OS
automatically provides one. The default network configure script
is /etc/qemu-ifup and the default network deconfigure script is
/etc/qemu-ifdown. Use script=no or downscript=no to disable
script execution.
If running QEMU as an unprivileged user, use the network helper
to configure the TAP interface and attach it to the bridge. The
default network helper executable is /path/to/qemu-bridge-helper
and the default bridge device is br0.
fd=h can be used to specify the handle of an already opened host
TAP interface.
Examples:
#launch a QEMU instance with the default network script
qemu-system-x86_64 linux.img -nic tap
#launch a QEMU instance with two NICs, each one connected
#to a TAP device
qemu-system-x86_64 linux.img \
-netdev tap,id=nd0,ifname=tap0 -device e1000,netdev=nd0 \
-netdev tap,id=nd1,ifname=tap1 -device rtl8139,netdev=nd1
#launch a QEMU instance with the default network helper to
#connect a TAP device to bridge br0
qemu-system-x86_64 linux.img -device virtio-net-pci,netdev=n1 \
-netdev tap,id=n1,"helper=/path/to/qemu-bridge-helper"
-netdev bridge,id=id[,br=bridge][,helper=helper]
Connect a host TAP network interface to a host bridge device.
Use the network helper helper to configure the TAP interface and
attach it to the bridge. The default network helper executable
is /path/to/qemu-bridge-helper and the default bridge device is
br0.
Examples:
#launch a QEMU instance with the default network helper to
#connect a TAP device to bridge br0
qemu-system-x86_64 linux.img -netdev bridge,id=n1 -device virtio-net,netdev=n1
#launch a QEMU instance with the default network helper to
#connect a TAP device to bridge qemubr0
qemu-system-x86_64 linux.img -netdev bridge,br=qemubr0,id=n1 -device virtio-net,netdev=n1
-netdev socket,id=id[,fd=h][,listen=[host]:port][,connect=host:port]
This host network backend can be used to connect the guest's
network to another QEMU virtual machine using a TCP socket
connection. If listen is specified, QEMU waits for incoming
connections on port (host is optional). connect is used to
connect to another QEMU instance using the listen option. fd=h
specifies an already opened TCP socket.
Example:
# launch a first QEMU instance
qemu-system-x86_64 linux.img \
-device e1000,netdev=n1,mac=52:54:00:12:34:56 \
-netdev socket,id=n1,listen=:1234
# connect the network of this instance to the network of the first instance
qemu-system-x86_64 linux.img \
-device e1000,netdev=n2,mac=52:54:00:12:34:57 \
-netdev socket,id=n2,connect=127.0.0.1:1234
-netdev socket,id=id[,fd=h][,mcast=maddr:port[,localaddr=addr]]
Configure a socket host network backend to share the guest's
network traffic with another QEMU virtual machines using a UDP
multicast socket, effectively making a bus for every QEMU with
same multicast address maddr and port. NOTES:
1. Several QEMU can be running on different hosts and share same
bus (assuming correct multicast setup for these hosts).
2. mcast support is compatible with User Mode Linux (argument
ethN=mcast), see .
3. Use fd=h to specify an already opened UDP multicast socket.
Example:
# launch one QEMU instance
qemu-system-x86_64 linux.img \
-device e1000,netdev=n1,mac=52:54:00:12:34:56 \
-netdev socket,id=n1,mcast=230.0.0.1:1234
# launch another QEMU instance on same "bus"
qemu-system-x86_64 linux.img \
-device e1000,netdev=n2,mac=52:54:00:12:34:57 \
-netdev socket,id=n2,mcast=230.0.0.1:1234
# launch yet another QEMU instance on same "bus"
qemu-system-x86_64 linux.img \
-device e1000,netdev=n3,mac=52:54:00:12:34:58 \
-netdev socket,id=n3,mcast=230.0.0.1:1234
Example (User Mode Linux compat.):
# launch QEMU instance (note mcast address selected is UML's default)
qemu-system-x86_64 linux.img \
-device e1000,netdev=n1,mac=52:54:00:12:34:56 \
-netdev socket,id=n1,mcast=239.192.168.1:1102
# launch UML
/path/to/linux ubd0=/path/to/root_fs eth0=mcast
Example (send packets from host's 1.2.3.4):
qemu-system-x86_64 linux.img \
-device e1000,netdev=n1,mac=52:54:00:12:34:56 \
-netdev socket,id=n1,mcast=239.192.168.1:1102,localaddr=1.2.3.4
-netdev
stream,id=str[,server=on|off],addr.type=inet,addr.host=host,addr.port=port[,to=maxport][,numeric=on|off][,keep-alive=on|off][,mptcp=on|off][,addr.ipv4=on|off][,addr.ipv6=on|off][,reconnect-ms=milliseconds]
Configure a network backend to connect to another QEMU virtual
machine or a proxy using a TCP/IP socket.
server=on|off
if on create a server socket
addr.host=host,addr.port=port
socket address to listen on (server=on) or connect to
(server=off)
to=maxport
if present, this is range of possible addresses, with
port between port and maxport.
numeric=on|off
if on host and port are guaranteed to be numeric,
otherwise a name resolution should be attempted (default:
off)
keep-alive=on|off
enable keep-alive when connecting to this socket. Not
supported for passive sockets.
mptcp=on|off
enable multipath TCP
ipv4=on|off
whether to accept IPv4 addresses, default to try both
IPv4 and IPv6
ipv6=on|off
whether to accept IPv6 addresses, default to try both
IPv4 and IPv6
reconnect-ms=milliseconds
for a client socket, if a socket is disconnected, then
attempt a reconnect after the given number of
milliseconds. Setting this to zero disables this
function. (default: 0)
Example (two guests connected using a TCP/IP socket):
# first VM
qemu-system-x86_64 linux.img \
-device virtio-net,netdev=net0,mac=52:54:00:12:34:56 \
-netdev stream,id=net0,server=on,addr.type=inet,addr.host=localhost,addr.port=1234
# second VM
qemu-system-x86_64 linux.img \
-device virtio-net,netdev=net0,mac=52:54:00:12:34:57 \
-netdev stream,id=net0,server=off,addr.type=inet,addr.host=localhost,addr.port=1234,reconnect-ms=5000
-netdev
stream,id=str[,server=on|off],addr.type=unix,addr.path=path[,abstract=on|off][,tight=on|off][,reconnect-ms=milliseconds]
Configure a network backend to connect to another QEMU virtual
machine or a proxy using a stream oriented unix domain socket.
server=on|off
if on create a server socket
addr.path=path
filesystem path to use
abstract=on|off
if on, this is a Linux abstract socket address.
tight=on|off
if false, pad an abstract socket address with enough null
bytes to make it fill struct sockaddr_un member sun_path.
reconnect-ms=milliseconds
for a client socket, if a socket is disconnected, then
attempt a reconnect after the given number of
milliseconds. Setting this to zero disables this
function. (default: 0)
Example (using passt as a replacement of -netdev user):
# start passt server as a non privileged user
passt
UNIX domain socket bound at /tmp/passt_1.socket
# start QEMU to connect to passt
qemu-system-x86_64 linux.img \
-device virtio-net,netdev=net0 \
-netdev stream,id=net0,server=off,addr.type=unix,addr.path=/tmp/passt_1.socket
Example (two guests connected using a stream oriented unix
domain socket):
# first VM
qemu-system-x86_64 linux.img \
-device virtio-net,netdev=net0,mac=52:54:00:12:34:56 \
netdev stream,id=net0,server=on,addr.type=unix,addr.path=/tmp/qemu0
# second VM
qemu-system-x86_64 linux.img \
-device virtio-net,netdev=net0,mac=52:54:00:12:34:57 \
-netdev stream,id=net0,server=off,addr.type=unix,addr.path=/tmp/qemu0,reconnect-ms=5000
-netdev
stream,id=str[,server=on|off],addr.type=fd,addr.str=file-descriptor[,reconnect-ms=milliseconds]
Configure a network backend to connect to another QEMU virtual
machine or a proxy using a stream oriented socket file
descriptor.
server=on|off
if on create a server socket
addr.str=file-descriptor
file descriptor number to use as a socket
reconnect-ms=milliseconds
for a client socket, if a socket is disconnected, then
attempt a reconnect after the given number of
milliseconds. Setting this to zero disables this
function. (default: 0)
-netdev
dgram,id=str,remote.type=inet,remote.host=maddr,remote.port=port[,local.type=inet,local.host=addr]
Configure a network backend to connect to a multicast address.
remote.host=maddr,remote.port=port
multicast address
local.host=addr
specify the host address to send packets from
Example:
# launch one QEMU instance
qemu-system-x86_64 linux.img \
-device virtio-net,netdev=net0,mac=52:54:00:12:34:56 \
-netdev dgram,id=net0,remote.type=inet,remote.host=224.0.0.1,remote.port=1234
# launch another QEMU instance on same "bus"
qemu-system-x86_64 linux.img \
-device virtio-net,netdev=net0,mac=52:54:00:12:34:57 \
-netdev dgram,id=net0,remote.type=inet,remote.host=224.0.0.1,remote.port=1234
# launch yet another QEMU instance on same "bus"
qemu-system-x86_64 linux.img \
-device virtio-net,netdev=net0,mac=52:54:00:12:34:58 \
-netdev dgram,id=net0,remote.type=inet,remote.host=224.0.0.1,remote.port=1234
-netdev
dgram,id=str,remote.type=inet,remote.host=maddr,remote.port=port[,local.type=fd,local.str=file-descriptor]
Configure a network backend to connect to a multicast address
using a UDP socket file descriptor.
remote.host=maddr,remote.port=port
multicast address
local.str=file-descriptor
File descriptor to use to send packets
-netdev
dgram,id=str,local.type=inet,local.host=addr,local.port=port[,remote.type=inet,remote.host=addr,remote.port=port]
Configure a network backend to connect to another QEMU virtual
machine or a proxy using a datagram oriented unix domain socket.
local.host=addr,local.port=port
IP address to use to send the packets from
remote.host=addr,remote.port=port
Destination IP address
Example (two guests connected using an UDP/IP socket):
# first VM
qemu-system-x86_64 linux.img \
-device virtio-net,netdev=net0,mac=52:54:00:12:34:56 \
-netdev dgram,id=net0,local.type=inet,local.host=localhost,local.port=1234,remote.type=inet,remote.host=localhost,remote.port=1235
# second VM
qemu-system-x86_64 linux.img \
-device virtio-net,netdev=net0,mac=52:54:00:12:34:56 \
-netdev dgram,id=net0,local.type=inet,local.host=localhost,local.port=1235,remote.type=inet,remote.host=localhost,remote.port=1234
-netdev
dgram,id=str,local.type=unix,local.path=path[,remote.type=unix,remote.path=path]
Configure a network backend to connect to another QEMU virtual
machine or a proxy using a datagram oriented unix socket.
local.path=path
filesystem path to use to bind the socket
remote.path=path
filesystem path to use as a destination (see sendto(2))
Example (two guests connected using an UDP/UNIX socket):
# first VM
qemu-system-x86_64 linux.img \
-device virtio-net,netdev=net0,mac=52:54:00:12:34:56 \
-netdev dgram,id=net0,local.type=unix,local.path=/tmp/qemu0,remote.type=unix,remote.path=/tmp/qemu1
# second VM
qemu-system-x86_64 linux.img \
-device virtio-net,netdev=net0,mac=52:54:00:12:34:57 \
-netdev dgram,id=net0,local.type=unix,local.path=/tmp/qemu1,remote.type=unix,remote.path=/tmp/qemu0
-netdev dgram,id=str,local.type=fd,local.str=file-descriptor
Configure a network backend to connect to another QEMU virtual
machine or a proxy using a datagram oriented socket file
descriptor.
local.str=file-descriptor
File descriptor to use to send packets
-netdev
l2tpv3,id=id,src=srcaddr,dst=dstaddr[,srcport=srcport][,dstport=dstport],txsession=txsession[,rxsession=rxsession][,ipv6=on|off][,udp=on|off][,cookie64=on|off][,counter=on|off][,pincounter=on|off][,txcookie=txcookie][,rxcookie=rxcookie][,offset=offset]
Configure a L2TPv3 pseudowire host network backend. L2TPv3
(RFC3931) is a popular protocol to transport Ethernet (and other
Layer 2) data frames between two systems. It is present in
routers, firewalls and the Linux kernel (from version 3.3
onwards).
This transport allows a VM to communicate to another VM, router
or firewall directly.
src=srcaddr
source address (mandatory)
dst=dstaddr
destination address (mandatory)
udp=on select udp encapsulation (default is ip).
srcport=srcport
source udp port.
dstport=dstport
destination udp port.
ipv6=on
force v6, otherwise defaults to v4.
rxcookie=rxcookie; txcookie=txcookie
Cookies are a weak form of security in the l2tpv3
specification. Their function is mostly to prevent
misconfiguration. By default they are 32 bit.
cookie64=on
Set cookie size to 64 bit instead of the default 32
counter=off
Force a 'cut-down' L2TPv3 with no counter as in
draft-mkonstan-l2tpext-keyed-ipv6-tunnel-00
pincounter=on
Work around broken counter handling in peer. This may
also help on networks which have packet reorder.
offset=offset
Add an extra offset between header and data
For example, to attach a VM running on host 4.3.2.1 via L2TPv3
to the bridge br-lan on the remote Linux host 1.2.3.4:
# Setup tunnel on linux host using raw ip as encapsulation
# on 1.2.3.4
ip l2tp add tunnel remote 4.3.2.1 local 1.2.3.4 tunnel_id 1 peer_tunnel_id 1 \
encap udp udp_sport 16384 udp_dport 16384
ip l2tp add session tunnel_id 1 name vmtunnel0 session_id \
0xFFFFFFFF peer_session_id 0xFFFFFFFF
ifconfig vmtunnel0 mtu 1500
ifconfig vmtunnel0 up
brctl addif br-lan vmtunnel0
# on 4.3.2.1
# launch QEMU instance - if your network has reorder or is very lossy add ,pincounter
qemu-system-x86_64 linux.img -device e1000,netdev=n1 \
-netdev l2tpv3,id=n1,src=4.2.3.1,dst=1.2.3.4,udp=on,srcport=16384,dstport=16384,rxsession=0xffffffff,txsession=0xffffffff,counter=on
-netdev
vde,id=id[,sock=socketpath][,port=n][,group=groupname][,mode=octalmode]
Configure VDE backend to connect to PORT n of a vde switch
running on host and listening for incoming connections on
socketpath. Use GROUP groupname and MODE octalmode to change
default ownership and permissions for communication port. This
option is only available if QEMU has been compiled with vde
support enabled.
Example:
# launch vde switch
vde_switch -F -sock /tmp/myswitch
# launch QEMU instance
qemu-system-x86_64 linux.img -nic vde,sock=/tmp/myswitch
-netdev
af-xdp,id=str,ifname=name[,mode=native|skb][,force-copy=on|off][,queues=n][,start-queue=m][,inhibit=on|off][,sock-fds=x:y:...:z][,map-path=/path/to/socket/map][,map-start-index=i]
Configure AF_XDP backend to connect to a network interface
'name' using AF_XDP socket. A specific program attach mode for
a default XDP program can be forced with 'mode', defaults to
best-effort, where the likely most performant mode will be in
use. Number of queues 'n' should generally match the number or
queues in the interface, defaults to 1. Traffic arriving on
non-configured device queues will not be delivered to the
network backend.
# set number of queues to 4
ethtool -L eth0 combined 4
# launch QEMU instance
qemu-system-x86_64 linux.img -device virtio-net-pci,netdev=n1 \
-netdev af-xdp,id=n1,ifname=eth0,queues=4
'start-queue' option can be specified if a particular range of
queues [m, m + n] should be in use. For example, this is may be
necessary in order to use certain NICs in native mode. Kernel
allows the driver to create a separate set of XDP queues on top
of regular ones, and only these queues can be used for AF_XDP
sockets. NICs that work this way may also require an additional
traffic redirection with ethtool to these special queues.
# set number of queues to 1
ethtool -L eth0 combined 1
# redirect all the traffic to the second queue (id: 1)
# note: drivers may require non-empty key/mask pair.
ethtool -N eth0 flow-type ether \
dst 00:00:00:00:00:00 m FF:FF:FF:FF:FF:FE action 1
ethtool -N eth0 flow-type ether \
dst 00:00:00:00:00:01 m FF:FF:FF:FF:FF:FE action 1
# launch QEMU instance
qemu-system-x86_64 linux.img -device virtio-net-pci,netdev=n1 \
-netdev af-xdp,id=n1,ifname=eth0,queues=1,start-queue=1
XDP program can also be loaded externally. In this case
'inhibit' option should be set to 'on'. Either 'sock-fds' or
'map-path' can be used with 'inhibit' enabled. 'sock-fds' can
be provided with file descriptors for already open but not bound
XDP sockets already added to a socket map for corresponding
queues. One socket per queue.
qemu-system-x86_64 linux.img -device virtio-net-pci,netdev=n1 \
-netdev af-xdp,id=n1,ifname=eth0,queues=3,inhibit=on,sock-fds=15:16:17
For the 'inhibit' option set to 'on' used together with
'map-path' it is expected that the XDP program with the socket
map is already loaded on the networking device and the map
pinned into BPF file system. The path to the pinned map is then
passed to QEMU which then creates the file descriptors and
inserts them into the existing socket map.
qemu-system-x86_64 linux.img -device virtio-net-pci,netdev=n1 \
-netdev af-xdp,id=n1,ifname=eth0,queues=2,inhibit=on,map-path=/sys/fs/bpf/xsks_map
Additionally, 'map-start-index' can be used to specify the start
offset for insertion into the socket map. The combination of
'map-path' and 'sock-fds' together is not supported.
-netdev vhost-user,chardev=id[,vhostforce=on|off][,queues=n]
Establish a vhost-user netdev, backed by a chardev id. The
chardev should be a unix domain socket backed one. The
vhost-user uses a specifically defined protocol to pass vhost
ioctl replacement messages to an application on the other end of
the socket. On non-MSIX guests, the feature can be forced with
vhostforce. Use 'queues=n' to specify the number of queues to be
created for multiqueue vhost-user.
Example:
qemu -m 512 -object memory-backend-file,id=mem,size=512M,mem-path=/hugetlbfs,share=on \
-numa node,memdev=mem \
-chardev socket,id=chr0,path=/path/to/socket \
-netdev type=vhost-user,id=net0,chardev=chr0 \
-device virtio-net-pci,netdev=net0
-netdev vhost-vdpa[,vhostdev=/path/to/dev][,vhostfd=h]
Establish a vhost-vdpa netdev.
vDPA device is a device that uses a datapath which complies with
the virtio specifications with a vendor specific control path.
vDPA devices can be both physically located on the hardware or
emulated by software.
-netdev hubport,id=id,hubid=hubid[,netdev=nd]
Create a hub port on the emulated hub with ID hubid.
The hubport netdev lets you connect a NIC to a QEMU emulated hub
instead of a single netdev. Alternatively, you can also connect
the hubport to another netdev with ID nd by using the netdev=nd
option.
-net nic[,netdev=nd][,macaddr=mac][,model=type]
[,name=name][,addr=addr][,vectors=v]
Legacy option to configure or create an on-board (or machine
default) Network Interface Card(NIC) and connect it either to
the emulated hub with ID 0 (i.e. the default hub), or to the
netdev nd. If model is omitted, then the default NIC model
associated with the machine type is used. Note that the default
NIC model may change in future QEMU releases, so it is highly
recommended to always specify a model. Optionally, the MAC
address can be changed to mac, the device address set to addr
(PCI cards only), and a name can be assigned for use in monitor
commands. Optionally, for PCI cards, you can specify the number
v of MSI-X vectors that the card should have; this option
currently only affects virtio cards; set v = 0 to disable MSI-X.
If no -net option is specified, a single NIC is created. QEMU
can emulate several different models of network card. Use -net
nic,model=help for a list of available devices for your target.
-net user|passt|tap|bridge|socket|l2tpv3|vde[,...][,name=name]
Configure a host network backend (with the options corresponding
to the same -netdev option) and connect it to the emulated hub 0
(the default hub). Use name to specify the name of the hub port.
Character device options
The general form of a character device option is:
-chardev backend,id=id[,mux=on|off][,options]
Backend is one of: null, socket, udp, msmouse, hub, vc, ringbuf,
file, pipe, console, serial, pty, stdio, braille, parallel,
spicevmc, spiceport. The specific backend will determine the
applicable options.
Use -chardev help to print all available chardev backend types.
All devices must have an id, which can be any string up to 127
characters long. It is used to uniquely identify this device in
other command line directives.
A character device may be used in multiplexing mode by multiple
front-ends. Specify mux=on to enable this mode. A multiplexer is
a "1:N" device, and here the "1" end is your specified chardev
backend, and the "N" end is the various parts of QEMU that can
talk to a chardev. If you create a chardev with id=myid and
mux=on, QEMU will create a multiplexer with your specified ID,
and you can then configure multiple front ends to use that
chardev ID for their input/output. Up to four different front
ends can be connected to a single multiplexed chardev. (Without
multiplexing enabled, a chardev can only be used by a single
front end.) For instance you could use this to allow a single
stdio chardev to be used by two serial ports and the QEMU
monitor:
-chardev stdio,mux=on,id=char0 \
-mon chardev=char0,mode=readline \
-serial chardev:char0 \
-serial chardev:char0
You can have more than one multiplexer in a system
configuration; for instance you could have a TCP port
multiplexed between UART 0 and UART 1, and stdio multiplexed
between the QEMU monitor and a parallel port:
-chardev stdio,mux=on,id=char0 \
-mon chardev=char0,mode=readline \
-parallel chardev:char0 \
-chardev tcp,...,mux=on,id=char1 \
-serial chardev:char1 \
-serial chardev:char1
When you're using a multiplexed character device, some escape
sequences are interpreted in the input. See the chapter about
Keys in the character backend multiplexer <#keys-in-the-
character-backend-multiplexer> in the System Emulation Users
Guide for more details.
Note that some other command line options may implicitly create
multiplexed character backends; for instance -serial mon:stdio
creates a multiplexed stdio backend connected to the serial port
and the QEMU monitor, and -nographic also multiplexes the
console and the monitor to stdio.
If you need to aggregate data in the opposite direction (where
one QEMU frontend interface receives input and output from
multiple backend chardev devices), please refer to the paragraph
below regarding chardev hub aggregator device configuration.
Every backend supports the logfile option, which supplies the
path to a file to record all data transmitted via the backend.
The logappend option controls whether the log file will be
truncated or appended to when opened.
The available backends are:
-chardev null,id=id
A void device. This device will not emit any data, and will drop
any data it receives. The null backend does not take any
options.
-chardev socket,id=id[,TCP options or unix
options][,server=on|off][,wait=on|off][,telnet=on|off][,websocket=on|off][,reconnect-ms=milliseconds][,tls-creds=id][,tls-authz=id]
Create a two-way stream socket, which can be either a TCP or a
unix socket. A unix socket will be created if path is specified.
Behaviour is undefined if TCP options are specified for a unix
socket.
server=on|off specifies that the socket shall be a listening
socket.
wait=on|off specifies that QEMU should not block waiting for a
client to connect to a listening socket.
telnet=on|off specifies that traffic on the socket should
interpret telnet escape sequences.
websocket=on|off specifies that the socket uses WebSocket
protocol for communication.
reconnect-ms sets the timeout for reconnecting on non-server
sockets when the remote end goes away. qemu will delay this many
milliseconds and then attempt to reconnect. Zero disables
reconnecting, and is the default.
tls-creds requests enablement of the TLS protocol for
encryption, and specifies the id of the TLS credentials to use
for the handshake. The credentials must be previously created
with the -object tls-creds argument.
tls-auth provides the ID of the QAuthZ authorization object
against which the client's x509 distinguished name will be
validated. This object is only resolved at time of use, so can
be deleted and recreated on the fly while the chardev server is
active. If missing, it will default to denying access.
TCP and unix socket options are given below:
TCP options:
port=port[,host=host][,to=to][,ipv4=on|off][,ipv6=on|off][,nodelay=on|off]
host for a listening socket specifies the local address
to be bound. For a connecting socket species the remote
host to connect to. host is optional for listening
sockets. If not specified it defaults to 0.0.0.0.
port for a listening socket specifies the local port to
be bound. For a connecting socket specifies the port on
the remote host to connect to. port can be given as
either a port number or a service name. port is required.
to is only relevant to listening sockets. If it is
specified, and port cannot be bound, QEMU will attempt to
bind to subsequent ports up to and including to until it
succeeds. to must be specified as a port number.
ipv4=on|off and ipv6=on|off specify that either IPv4 or
IPv6 must be used. If neither is specified the socket may
use either protocol.
nodelay=on|off disables the Nagle algorithm.
unix options: path=path[,abstract=on|off][,tight=on|off]
path specifies the local path of the unix socket. path is
required. abstract=on|off specifies the use of the
abstract socket namespace, rather than the filesystem.
Optional, defaults to false. tight=on|off sets the
socket length of abstract sockets to their minimum,
rather than the full sun_path length. Optional, defaults
to true.
-chardev
udp,id=id[,host=host],port=port[,localaddr=localaddr][,localport=localport][,ipv4=on|off][,ipv6=on|off]
Sends all traffic from the guest to a remote host over UDP.
host specifies the remote host to connect to. If not specified
it defaults to localhost.
port specifies the port on the remote host to connect to. port
is required.
localaddr specifies the local address to bind to. If not
specified it defaults to 0.0.0.0.
localport specifies the local port to bind to. If not specified
any available local port will be used.
ipv4=on|off and ipv6=on|off specify that either IPv4 or IPv6
must be used. If neither is specified the device may use either
protocol.
-chardev msmouse,id=id
Forward QEMU's emulated msmouse events to the guest. msmouse
does not take any options.
-chardev hub,id=id,chardevs.0=id[,chardevs.N=id]
Explicitly create chardev backend hub device with the
possibility to aggregate input from multiple backend devices and
forward it to a single frontend device. Additionally, hub device
takes the output from the frontend device and sends it back to
all the connected backend devices. This allows for seamless
interaction between different backend devices and a single
frontend interface. Aggregation supported for up to 4 chardev
devices. (Since 10.0)
For example, the following is a use case of 2 backend devices:
virtual console vc0 and a pseudo TTY pty0 connected to a single
virtio hvc console frontend device with a hub hub0 help. Virtual
console renders text to an image, which can be shared over the
VNC protocol. In turn, pty backend provides bidirectional
communication to the virtio hvc console over the pseudo TTY
file. The example configuration can be as follows:
-chardev pty,path=/tmp/pty,id=pty0 \
-chardev vc,id=vc0 \
-chardev hub,id=hub0,chardevs.0=pty0,chardevs.1=vc0 \
-device virtconsole,chardev=hub0 \
-vnc 0.0.0.0:0
Once QEMU starts VNC client and any TTY emulator can be used to
control a single hvc console:
# Start TTY emulator
tio /tmp/pty
# Start VNC client and switch to virtual console Ctrl-Alt-2
vncviewer :0
Several frontend devices is not supported. Stacking of
multiplexers and hub devices is not supported as well.
-chardev
vc,id=id[[,width=width][,height=height]][[,cols=cols][,rows=rows]]
Connect to a QEMU text console. vc may optionally be given a
specific size.
width and height specify the width and height respectively of
the console, in pixels.
cols and rows specify that the console be sized to fit a text
console with the given dimensions.
-chardev ringbuf,id=id[,size=size]
Create a ring buffer with fixed size size. size must be a power
of two and defaults to 64K.
-chardev file,id=id,path=path[,input-path=input-path]
Log all traffic received from the guest to a file.
path specifies the path of the file to be opened. This file will
be created if it does not already exist, and overwritten if it
does. path is required.
If input-path is specified, this is the path of a second file
which will be used for input. If input-path is not specified, no
input will be available from the chardev.
Note that input-path is not supported on Windows hosts.
-chardev pipe,id=id,path=path
Create a two-way connection to the guest. The behaviour differs
slightly between Windows hosts and other hosts:
On Windows, a single duplex pipe will be created at
\\.pipe\path.
On other hosts, 2 pipes will be created called path.in and
path.out. Data written to path.in will be received by the guest.
Data written by the guest can be read from path.out. QEMU will
not create these fifos, and requires them to be present.
path forms part of the pipe path as described above. path is
required.
-chardev console,id=id
Send traffic from the guest to QEMU's standard output. console
does not take any options.
console is only available on Windows hosts.
-chardev serial,id=id,path=path
Send traffic from the guest to a serial device on the host.
On Unix hosts serial will actually accept any tty device, not
only serial lines.
path specifies the name of the serial device to open.
-chardev pty,id=id[,path=path]
Create a new pseudo-terminal on the host and connect to it.
pty is not available on Windows hosts.
If path is specified, QEMU will create a symbolic link at that
location which points to the new PTY device.
This avoids having to make QMP or HMP monitor queries to find
out what the new PTY device path is.
Note that while QEMU will remove the symlink when it exits
gracefully, it will not do so in case of crashes or on certain
startup errors. It is recommended that the user checks and
removes the symlink after QEMU terminates to account for this.
-chardev stdio,id=id[,signal=on|off]
Connect to standard input and standard output of the QEMU
process.
signal controls if signals are enabled on the terminal, that
includes exiting QEMU with the key sequence Control-c. This
option is enabled by default, use signal=off to disable it.
-chardev braille,id=id
Connect to a local BrlAPI server. braille does not take any
options.
-chardev parallel,id=id,path=path
parallel is only available on Linux, FreeBSD and DragonFlyBSD
hosts.
Connect to a local parallel port.
path specifies the path to the parallel port device. path
is required.
-chardev spicevmc,id=id,debug=debug,name=name
spicevmc is only available when spice support is built in.
debug debug level for spicevmc
name name of spice channel to connect to
Connect to a spice virtual machine channel, such as vdiport.
-chardev spiceport,id=id,debug=debug,name=name
spiceport is only available when spice support is built in.
debug debug level for spicevmc
name name of spice port to connect to
Connect to a spice port, allowing a Spice client to handle the
traffic identified by a name (preferably a fqdn).
TPM device options
The general form of a TPM device option is:
-tpmdev backend,id=id[,options]
The specific backend type will determine the applicable options.
The -tpmdev option creates the TPM backend and requires a
-device option that specifies the TPM frontend interface model.
Use -tpmdev help to print all available TPM backend types.
The available backends are:
-tpmdev passthrough,id=id,path=path,cancel-path=cancel-path
(Linux-host only) Enable access to the host's TPM using the
passthrough driver.
path specifies the path to the host's TPM device, i.e., on a
Linux host this would be /dev/tpm0. path is optional and by
default /dev/tpm0 is used.
cancel-path specifies the path to the host TPM device's sysfs
entry allowing for cancellation of an ongoing TPM command.
cancel-path is optional and by default QEMU will search for the
sysfs entry to use.
Some notes about using the host's TPM with the passthrough
driver:
The TPM device accessed by the passthrough driver must not be
used by any other application on the host.
Since the host's firmware (BIOS/UEFI) has already initialized
the TPM, the VM's firmware (BIOS/UEFI) will not be able to
initialize the TPM again and may therefore not show a
TPM-specific menu that would otherwise allow the user to
configure the TPM, e.g., allow the user to enable/disable or
activate/deactivate the TPM. Further, if TPM ownership is
released from within a VM then the host's TPM will get disabled
and deactivated. To enable and activate the TPM again
afterwards, the host has to be rebooted and the user is required
to enter the firmware's menu to enable and activate the TPM. If
the TPM is left disabled and/or deactivated most TPM commands
will fail.
To create a passthrough TPM use the following two options:
-tpmdev passthrough,id=tpm0 -device tpm-tis,tpmdev=tpm0
Note that the -tpmdev id is tpm0 and is referenced by
tpmdev=tpm0 in the device option.
-tpmdev emulator,id=id,chardev=dev
(Linux-host only) Enable access to a TPM emulator using Unix
domain socket based chardev backend.
chardev specifies the unique ID of a character device backend
that provides connection to the software TPM server.
To create a TPM emulator backend device with chardev socket
backend:
-chardev socket,id=chrtpm,path=/tmp/swtpm-sock -tpmdev emulator,id=tpm0,chardev=chrtpm -device tpm-tis,tpmdev=tpm0
Boot Image or Kernel specific
There are broadly 4 ways you can boot a system with QEMU.
o specify a firmware and let it control finding a kernel
o specify a firmware and pass a hint to the kernel to boot
o direct kernel image boot
o manually load files into the guest's address space
The third method is useful for quickly testing kernels but as there is
no firmware to pass configuration information to the kernel the
hardware must either be probeable, the kernel built for the exact
configuration or passed some configuration data (e.g. a DTB blob) which
tells the kernel what drivers it needs. This exact details are often
hardware specific.
The final method is the most generic way of loading images into the
guest address space and used mostly for bare metal type development
where the reset vectors of the processor are taken into account.
For x86 machines and some other architectures -bios will generally do
the right thing with whatever it is given. For other machines the more
strict -pflash option needs an image that is sized for the flash device
for the given machine type.
Please see the QEMU System Emulator Targets <#system-targets-ref>
section of the manual for more detailed documentation.
-bios file
Set the filename for the BIOS.
-pflash file
Use file as a parallel flash image.
The kernel options were designed to work with Linux kernels although
other things (like hypervisors) can be packaged up as a kernel
executable image. The exact format of a executable image is usually
architecture specific.
The way in which the kernel is started (what address it is loaded at,
what if any information is passed to it via CPU registers, the state of
the hardware when it is started, and so on) is also architecture
specific. Typically it follows the specification laid down by the Linux
kernel for how kernels for that architecture must be started.
-kernel bzImage
Use bzImage as kernel image. The kernel can be either a Linux
kernel or in multiboot format.
-shim shim.efi
Use 'shim.efi' to boot the kernel
-append cmdline
Use cmdline as kernel command line
-initrd file
Use file as initial ram disk.
-initrd "file1 arg=foo,file2"
This syntax is only available with multiboot.
Use file1 and file2 as modules and pass arg=foo as parameter to
the first module. Commas can be provided in module parameters by
doubling them on the command line to escape them:
-initrd "bzImage earlyprintk=xen,,keep root=/dev/xvda1,initrd.img"
Multiboot only. Use bzImage as the first module with
"earlyprintk=xen,keep root=/dev/xvda1" as its command line, and
initrd.img as the second module.
-dtb file
Use file as a device tree binary (dtb) image and pass it to the
kernel on boot.
Finally you can also manually load images directly into the address
space of the guest. This is most useful for developers who already know
the layout of their guest and take care to ensure something sane will
happen when the reset vector executes.
The generic loader can be invoked by using the loader device:
-device
loader,addr=,data=,data-len=[,data-be=][,cpu-num=]
there is also the guest loader which operates in a similar way but
tweaks the DTB so a hypervisor loaded via -kernel can find where the
guest image is:
-device
guest-loader,addr=[,kernel=,[bootargs=]][,initrd=]
Debug/Expert options
-compat
[deprecated-input=][,deprecated-output=]
Set policy for handling deprecated management interfaces
(experimental):
deprecated-input=accept (default)
Accept deprecated commands and arguments
deprecated-input=reject
Reject deprecated commands and arguments
deprecated-input=crash
Crash on deprecated commands and arguments
deprecated-output=accept (default)
Emit deprecated command results and events
deprecated-output=hide
Suppress deprecated command results and events
Limitation: covers only syntactic aspects of QMP.
-compat
[unstable-input=][,unstable-output=]
Set policy for handling unstable management interfaces
(experimental):
unstable-input=accept (default)
Accept unstable commands and arguments
unstable-input=reject
Reject unstable commands and arguments
unstable-input=crash
Crash on unstable commands and arguments
unstable-output=accept (default)
Emit unstable command results and events
unstable-output=hide
Suppress unstable command results and events
Limitation: covers only syntactic aspects of QMP.
-fw_cfg [name=]name,file=file
Add named fw_cfg entry with contents from file file. If the
filename contains comma, you must double it (for instance,
"file=my,,file" to use file "my,file").
-fw_cfg [name=]name,string=str
Add named fw_cfg entry with contents from string str. If the
string contains comma, you must double it (for instance,
"string=my,,string" to use file "my,string").
The terminating NUL character of the contents of str will not be
included as part of the fw_cfg item data. To insert contents
with embedded NUL characters, you have to use the file
parameter.
The fw_cfg entries are passed by QEMU through to the guest.
Example:
-fw_cfg name=opt/com.mycompany/blob,file=./my_blob.bin
creates an fw_cfg entry named opt/com.mycompany/blob with
contents from ./my_blob.bin.
-serial dev
Redirect the virtual serial port to host character device dev.
The default device is vc in graphical mode and stdio in non
graphical mode.
This option can be used several times to simulate multiple
serial ports.
You can use -serial none to suppress the creation of default
serial devices.
Available character devices are:
vc[:WxH]
Virtual console. Optionally, a width and height can be
given in pixel with
vc:800x600
It is also possible to specify width or height in
characters:
vc:80Cx24C
pty[:path]
[Linux only] Pseudo TTY (a new PTY is automatically
allocated).
If path is specified, QEMU will create a symbolic link at
that location which points to the new PTY device.
This avoids having to make QMP or HMP monitor queries to
find out what the new PTY device path is.
Note that while QEMU will remove the symlink when it
exits gracefully, it will not do so in case of crashes or
on certain startup errors. It is recommended that the
user checks and removes the symlink after QEMU terminates
to account for this.
none No device is allocated. Note that for machine types which
emulate systems where a serial device is always present
in real hardware, this may be equivalent to the null
option, in that the serial device is still present but
all output is discarded. For boards where the number of
serial ports is truly variable, this suppresses the
creation of the device.
null A guest will see the UART or serial device as present in
the machine, but all output is discarded, and there is no
input. Conceptually equivalent to redirecting the output
to /dev/null.
chardev:id
Use a named character device defined with the -chardev
option.
/dev/XXX
[Linux only] Use host tty, e.g. /dev/ttyS0. The host
serial port parameters are set according to the emulated
ones.
/dev/parportN
[Linux only, parallel port only] Use host parallel port
N. Currently SPP and EPP parallel port features can be
used.
file:filename
Write output to filename. No character can be read.
stdio [Unix only] standard input/output
pipe:filename
name pipe filename
COMn [Windows only] Use host serial port n
udp:[remote_host]:remote_port[@[src_ip]:src_port]
This implements UDP Net Console. When remote_host or
src_ip are not specified they default to 0.0.0.0. When
not using a specified src_port a random port is
automatically chosen.
If you just want a simple readonly console you can use
netcat or nc, by starting QEMU with: -serial udp::4555
and nc as: nc -u -l -p 4555. Any time QEMU writes
something to that port it will appear in the netconsole
session.
If you plan to send characters back via netconsole or you
want to stop and start QEMU a lot of times, you should
have QEMU use the same source port each time by using
something like -serial udp::4555@:4556 to QEMU. Another
approach is to use a patched version of netcat which can
listen to a TCP port and send and receive characters via
udp. If you have a patched version of netcat which
activates telnet remote echo and single char transfer,
then you can use the following options to set up a netcat
redirector to allow telnet on port 5555 to access the
QEMU port.
QEMU Options:
-serial udp::4555@:4556
netcat options:
-u -P 4555 -L 0.0.0.0:4556 -t -p 5555 -I -T
telnet options:
localhost 5555
tcp:[host]:port[,server=on|off][,wait=on|off][,nodelay=on|off][,reconnect-ms=milliseconds]
The TCP Net Console has two modes of operation. It can
send the serial I/O to a location or wait for a
connection from a location. By default the TCP Net
Console is sent to host at the port. If you use the
server=on option QEMU will wait for a client socket
application to connect to the port before continuing,
unless the wait=on|off option was specified. The
nodelay=on|off option disables the Nagle buffering
algorithm. The reconnect-ms option only applies if
server=no is set, if the connection goes down it will
attempt to reconnect at the given interval. If host is
omitted, 0.0.0.0 is assumed. Only one TCP connection at a
time is accepted. You can use telnet=on to connect to the
corresponding character device.
Example to send tcp console to 192.168.0.2 port 4444
-serial
Example to listen and wait on port 4444 for connection
-serial
Example to not wait and listen on ip 192.168.0.100 port
4444 -serial
telnet:host:port[,server=on|off][,wait=on|off][,nodelay=on|off]
The telnet protocol is used instead of raw tcp sockets.
The options work the same as if you had specified -serial
tcp. The difference is that the port acts like a telnet
server or client using telnet option negotiation. This
will also allow you to send the MAGIC_SYSRQ sequence if
you use a telnet that supports sending the break
sequence. Typically in unix telnet you do it with
Control-] and then type "send break" followed by pressing
the enter key.
websocket:host:port,server=on[,wait=on|off][,nodelay=on|off]
The WebSocket protocol is used instead of raw tcp socket.
The port acts as a WebSocket server. Client mode is not
supported.
unix:path[,server=on|off][,wait=on|off][,reconnect-ms=milliseconds]
A unix domain socket is used instead of a tcp socket. The
option works the same as if you had specified -serial tcp
except the unix domain socket path is used for
connections.
mon:dev_string
This is a special option to allow the monitor to be
multiplexed onto another serial port. The monitor is
accessed with key sequence of Control-a and then pressing
c. dev_string should be any one of the serial devices
specified above. An example to multiplex the monitor onto
a telnet server listening on port 4444 would be:
-serial mon:telnet::4444,server=on,wait=off
When the monitor is multiplexed to stdio in this way,
Ctrl+C will not terminate QEMU any more but will be
passed to the guest instead.
braille
Braille device. This will use BrlAPI to display the
braille output on a real or fake device.
msmouse
Three button serial mouse. Configure the guest to use
Microsoft protocol.
-parallel dev
Redirect the virtual parallel port to host device dev (same
devices as the serial port). On Linux hosts, /dev/parportN can
be used to use hardware devices connected on the corresponding
host parallel port.
This option can be used several times to simulate up to 3
parallel ports.
Use -parallel none to disable all parallel ports.
-monitor dev
Redirect the monitor to host device dev (same devices as the
serial port). The default device is vc in graphical mode and
stdio in non graphical mode. Use -monitor none to disable the
default monitor.
-qmp dev
Like -monitor but opens in 'control' mode. For example, to make
QMP available on localhost port 4444:
-qmp tcp:localhost:4444,server=on,wait=off
Not all options are configurable via this syntax; for maximum
flexibility use the -mon option and an accompanying -chardev.
-qmp-pretty dev
Like -qmp but uses pretty JSON formatting.
-mon [chardev=]name[,mode=readline|control][,pretty=on|off]
Set up a monitor connected to the chardev name. QEMU supports
two monitors: the Human Monitor Protocol (HMP; for human
interaction), and the QEMU Monitor Protocol (QMP; a JSON
RPC-style protocol). The default is HMP; mode=control selects
QMP instead. pretty is only valid when mode=control, turning on
JSON pretty printing to ease human reading and debugging.
For example:
-chardev socket,id=mon1,host=localhost,port=4444,server=on,wait=off \
-mon chardev=mon1,mode=control,pretty=on
enables the QMP monitor on localhost port 4444 with
pretty-printing.
-debugcon dev
Redirect the debug console to host device dev (same devices as
the serial port). The debug console is an I/O port which is
typically port 0xe9; writing to that I/O port sends output to
this device. The default device is vc in graphical mode and
stdio in non graphical mode.
-pidfile file
Store the QEMU process PID in file. It is useful if you launch
QEMU from a script.
--preconfig
Pause QEMU for interactive configuration before the machine is
created, which allows querying and configuring properties that
will affect machine initialization. Use QMP command
'x-exit-preconfig' to exit the preconfig state and move to the
next state (i.e. run guest if -S isn't used or pause the second
time if -S is used). This option is experimental.
-S Do not start CPU at startup (you must type 'c' in the monitor).
-overcommit mem-lock=on|off|on-fault
-overcommit cpu-pm=on|off
Run qemu with hints about host resource overcommit. The default
is to assume that host overcommits all resources.
Locking qemu and guest memory can be enabled via mem-lock=on or
mem-lock=on-fault (disabled by default). This works when host
memory is not overcommitted and reduces the worst-case latency
for guest. The on-fault option is better for reducing the memory
footprint since it makes allocations lazy, but the pages still
get locked in place once faulted by the guest or QEMU. Note that
the two options are mutually exclusive.
Guest ability to manage power state of host cpus (increasing
latency for other processes on the same host cpu, but decreasing
latency for guest) can be enabled via cpu-pm=on (disabled by
default). This works best when host CPU is not overcommitted.
When used, host estimates of CPU cycle and power utilization
will be incorrect, not taking into account guest idle time.
-gdb dev
Accept a gdb connection on device dev (see the GDB usage <#gdb-
usage> chapter in the System Emulation Users Guide). Note that
this option does not pause QEMU execution -- if you want QEMU to
not start the guest until you connect with gdb and issue a
continue command, you will need to also pass the -S option to
QEMU.
The most usual configuration is to listen on a local TCP socket:
-gdb tcp::3117
but you can specify other backends; UDP, pseudo TTY, or even
stdio are all reasonable use cases. For example, a stdio
connection allows you to start QEMU from within gdb and
establish the connection via a pipe:
(gdb) target remote | exec qemu-system-x86_64 -gdb stdio ...
-s Shorthand for -gdb , i.e. open a gdbserver on TCP
port 1234 (see the GDB usage <#gdb-usage> chapter in the System
Emulation Users Guide).
-d item1[,...]
Enable logging of specified items. Use '-d help' for a list of
log items.
-D logfile
Output log in logfile instead of to stderr
-dfilter range1[,...]
Filter debug output to that relevant to a range of target
addresses. The filter spec can be either start+size, start-size
or start..end where start end and size are the addresses and
sizes required. For example:
-dfilter 0x8000..0x8fff,0xffffffc000080000+0x200,0xffffffc000060000-0x1000
Will dump output for any code in the 0x1000 sized block starting
at 0x8000 and the 0x200 sized block starting at
0xffffffc000080000 and another 0x1000 sized block starting at
0xffffffc00005f000.
-seed number
Force the guest to use a deterministic pseudo-random number
generator, seeded with number. This does not affect crypto
routines within the host.
-L path
Set the directory for the BIOS, VGA BIOS and keymaps.
To list all the data directories, use -L help.
-enable-kvm
Enable KVM full virtualization support. This option is only
available if KVM support is enabled when compiling.
-xen-domid id
Specify xen guest domain id (XEN only).
-xen-attach
Attach to existing xen domain. libxl will use this when starting
QEMU (XEN only). Restrict set of available xen operations to
specified domain id (XEN only).
-no-reboot
Exit instead of rebooting.
-no-shutdown
Don't exit QEMU on guest shutdown, but instead only stop the
emulation. This allows for instance switching to monitor to
commit changes to the disk image.
-action event=action
The action parameter serves to modify QEMU's default behavior
when certain guest events occur. It provides a generic method
for specifying the same behaviors that are modified by the
-no-reboot and -no-shutdown parameters.
Examples:
-action panic=none -action reboot=shutdown,shutdown=pause
-device i6300esb -action watchdog=pause
-loadvm file
Start right away with a saved state (loadvm in monitor)
-daemonize
Daemonize the QEMU process after initialization. QEMU will not
detach from standard IO until it is ready to receive connections
on any of its devices. This option is a useful way for external
programs to launch QEMU without having to cope with
initialization race conditions.
-option-rom file
Load the contents of file as an option ROM. This option is
useful to load things like EtherBoot.
-rtc
[base=utc|localtime|datetime][,clock=host|rt|vm][,driftfix=none|slew]
Specify base as utc or localtime to let the RTC start at the
current UTC or local time, respectively. localtime is required
for correct date in MS-DOS or Windows. To start at a specific
point in time, provide datetime in the format
2006-06-17T16:01:21 or 2006-06-17. The default base is UTC.
By default the RTC is driven by the host system time. This
allows using of the RTC as accurate reference clock inside the
guest, specifically if the host time is smoothly following an
accurate external reference clock, e.g. via NTP. If you want to
isolate the guest time from the host, you can set clock to rt
instead, which provides a host monotonic clock if host support
it. To even prevent the RTC from progressing during suspension,
you can set clock to vm (virtual clock). 'clock=vm' is
recommended especially in icount mode in order to preserve
determinism; however, note that in icount mode the speed of the
virtual clock is variable and can in general differ from the
host clock.
Enable driftfix (i386 targets only) if you experience time drift
problems, specifically with Windows' ACPI HAL. This option will
try to figure out how many timer interrupts were not processed
by the Windows guest and will re-inject them.
-icount
[shift=N|auto][,align=on|off][,sleep=on|off][,rr=record|replay,rrfile=filename[,rrsnapshot=snapshot]]
Enable virtual instruction counter. The virtual cpu will execute
one instruction every 2^N ns of virtual time. If auto is
specified then the virtual cpu speed will be automatically
adjusted to keep virtual time within a few seconds of real time.
Note that while this option can give deterministic behavior, it
does not provide cycle accurate emulation. Modern CPUs contain
superscalar out of order cores with complex cache hierarchies.
The number of instructions executed often has little or no
correlation with actual performance.
When the virtual cpu is sleeping, the virtual time will advance
at default speed unless sleep=off is specified. With sleep=off,
the virtual time will jump to the next timer deadline instantly
whenever the virtual cpu goes to sleep mode and will not advance
if no timer is enabled. This behavior gives deterministic
execution times from the guest point of view. The default if
icount is enabled is sleep=on. sleep=off cannot be used
together with either shift=auto or align=on.
align=on will activate the delay algorithm which will try to
synchronise the host clock and the virtual clock. The goal is to
have a guest running at the real frequency imposed by the shift
option. Whenever the guest clock is behind the host clock and if
align=on is specified then we print a message to the user to
inform about the delay. Currently this option does not work when
shift is auto. Note: The sync algorithm will work for those
shift values for which the guest clock runs ahead of the host
clock. Typically this happens when the shift value is high (how
high depends on the host machine). The default if icount is
enabled is align=off.
When the rr option is specified deterministic record/replay is
enabled. The rrfile= option must also be provided to specify the
path to the replay log. In record mode data is written to this
file, and in replay mode it is read back. If the rrsnapshot
option is given then it specifies a VM snapshot name. In record
mode, a new VM snapshot with the given name is created at the
start of execution recording. In replay mode this option
specifies the snapshot name used to load the initial VM state.
-watchdog-action action
The action controls what QEMU will do when the watchdog timer
expires. The default is reset (forcefully reset the guest).
Other possible actions are: shutdown (attempt to gracefully
shutdown the guest), poweroff (forcefully poweroff the guest),
inject-nmi (inject a NMI into the guest), pause (pause the
guest), debug (print a debug message and continue), or none (do
nothing).
Note that the shutdown action requires that the guest responds
to ACPI signals, which it may not be able to do in the sort of
situations where the watchdog would have expired, and thus
-watchdog-action shutdown is not recommended for production use.
Examples:
-device i6300esb -watchdog-action pause
-echr numeric_ascii_value
Change the escape character used for switching to the monitor
when using monitor and serial sharing. The default is 0x01 when
using the -nographic option. 0x01 is equal to pressing
Control-a. You can select a different character from the ascii
control keys where 1 through 26 map to Control-a through
Control-z. For instance you could use the either of the
following to change the escape character to Control-t.
-echr 0x14; -echr 20
The -incoming option specifies the migration channel for an incoming
migration. It may be used multiple times to specify multiple migration
channel types. The channel type is specified in , or is
'main' for all other forms of -incoming. If multiple -incoming options
are specified for a channel type, the last one takes precedence.
-incoming tcp:[host]:port[,to=maxport][,ipv4=on|off][,ipv6=on|off]
-incoming rdma:host:port[,ipv4=on|off][,ipv6=on|off]
Prepare for incoming migration, listen on a given tcp port.
-incoming unix:socketpath
Prepare for incoming migration, listen on a given unix socket.
-incoming fd:fd
Accept incoming migration from a given file descriptor.
-incoming file:filename[,offset=offset]
Accept incoming migration from a given file starting at offset.
offset allows the common size suffixes, or a 0x prefix, but not
both.
-incoming exec:cmdline
Accept incoming migration as an output from specified external
command.
-incoming
Accept incoming migration on the migration channel. For the
syntax of , see the QAPI documentation of
MigrationChannel. Examples:
-incoming '{"channel-type": "main",
"addr": { "transport": "socket",
"type": "unix",
"path": "my.sock" }}'
-incoming main,addr.transport=socket,addr.type=unix,addr.path=my.sock
-incoming defer
Wait for the URI to be specified via migrate_incoming. The
monitor can be used to change settings (such as migration
parameters) prior to issuing the migrate_incoming to allow the
migration to begin.
-only-migratable
Only allow migratable devices. Devices will not be allowed to
enter an unmigratable state.
-nodefaults
Don't create default devices. Normally, QEMU sets the default
devices like serial port, parallel port, virtual console,
monitor device, VGA adapter, floppy and CD-ROM drive and others.
The -nodefaults option will disable all those default devices.
-prom-env variable=value
Set OpenBIOS nvram variable to given value (PPC, SPARC only).
qemu-system-sparc -prom-env 'auto-boot?=false' \
-prom-env 'boot-device=sd(0,2,0):d' -prom-env 'boot-args=linux single'
qemu-system-ppc -prom-env 'auto-boot?=false' \
-prom-env 'boot-device=hd:2,\yaboot' \
-prom-env 'boot-args=conf=hd:2,\yaboot.conf'
-semihosting
Enable Semihosting <#semihosting> mode (ARM, M68K, Xtensa, MIPS,
RISC-V only).
Warning:
Note that this allows guest direct access to the host
filesystem, so should only be used with a trusted guest OS.
See the -semihosting-config option documentation for further
information about the facilities this enables.
-semihosting-config
[enable=on|off][,target=native|gdb|auto][,chardev=id][,userspace=on|off][,arg=str[,...]]
Enable and configure Semihosting <#semihosting> (ARM, M68K,
Xtensa, MIPS, RISC-V only).
Warning:
Note that this allows guest direct access to the host
filesystem, so should only be used with a trusted guest OS.
target=native|gdb|auto
Defines where the semihosting calls will be addressed, to
QEMU (native) or to GDB (gdb). The default is auto, which
means gdb during debug sessions and native otherwise.
chardev=str1
Send the output to a chardev backend output for native or
auto output when not in gdb
userspace=on|off
Allows code running in guest userspace to access the
semihosting interface. The default is that only
privileged guest code can make semihosting calls. Note
that setting userspace=on should only be used if all
guest code is trusted (for example, in bare-metal test
case code).
arg=str1,arg=str2,...
Allows the user to pass input arguments, and can be used
multiple times to build up a list. The old-style
-kernel/-append method of passing a command line is still
supported for backward compatibility. If both the
--semihosting-config arg and the -kernel/-append are
specified, the former is passed to semihosting as it
always takes precedence.
-sandbox
arg[,obsolete=string][,elevateprivileges=string][,spawn=string][,resourcecontrol=string]
Enable Seccomp mode 2 system call filter. 'on' will enable
syscall filtering and 'off' will disable it. The default is
'off'.
obsolete=string
Enable Obsolete system calls
elevateprivileges=string
Disable set*uid|gid system calls
spawn=string
Disable *fork and execve
resourcecontrol=string
Disable process affinity and schedular priority
-readconfig file
Read device configuration from file. This approach is useful
when you want to spawn QEMU process with many command line
options but you don't want to exceed the command line character
limit.
-no-user-config
The -no-user-config option makes QEMU not load any of the
user-provided config files on sysconfdir.
-trace [[enable=]pattern][,events=file][,file=file]
Specify tracing options.
[enable=]PATTERN
Immediately enable events matching PATTERN (either event name
or a globbing pattern). This option is only available if
QEMU has been compiled with the simple, log or ftrace tracing
backend. To specify multiple events or patterns, specify the
-trace option multiple times.
Use -trace help to print a list of names of trace points.
events=FILE
Immediately enable events listed in FILE. The file must
contain one event name (as listed in the trace-events-all
file) per line; globbing patterns are accepted too. This
option is only available if QEMU has been compiled with the
simple, log or ftrace tracing backend.
file=FILE
Log output traces to FILE. This option is only available if
QEMU has been compiled with the simple tracing backend.
-plugin file=file[,argname=argvalue]
Load a plugin.
file=file
Load the given plugin from a shared library file.
argname=argvalue
Argument passed to the plugin. (Can be given multiple
times.)
-run-with
[async-teardown=on|off][,chroot=dir][,exit-with-parent=on|off][,user=username|uid:gid]
Set QEMU process lifecycle options.
async-teardown=on enables asynchronous teardown. A new process
called "cleanup/" will be created at startup sharing
the address space with the main QEMU process, using clone. It
will wait for the main QEMU process to terminate completely, and
then exit. This allows QEMU to terminate very quickly even if
the guest was huge, leaving the teardown of the address space to
the cleanup process. Since the cleanup process shares the same
cgroups as the main QEMU process, accounting is performed
correctly. This only works if the cleanup process is not
forcefully killed with SIGKILL before the main QEMU process has
terminated completely.
chroot=dir can be used for doing a chroot to the specified
directory immediately before starting the guest execution. This
is especially useful in combination with user=....
exit-with-parent=on causes QEMU to exit if the parent process of
QEMU exits. This can be used when QEMU runs a captive
appliance, where the lifetime of the appliance is scoped to the
parent process. In case the parent process crashes, QEMU is
still cleaned up. This only works on Linux, FreeBSD and macOS
platforms.
user=username or user=uid:gid can be used to drop root
privileges before starting guest execution. QEMU will use the
setuid and setgid system calls to switch to the specified
identity. Note that the user=username syntax will also apply
the full set of supplementary groups for the user, whereas the
user=uid:gid will use only the gid group.
-msg [timestamp=on|off][,guest-name=on|off]
Control error message format.
timestamp=on|off
Prefix messages with a timestamp. Default is off.
guest-name=on|off
Prefix messages with guest name but only if -name guest
option is set otherwise the option is ignored. Default is
off.
-dump-vmstate file
Dump json-encoded vmstate information for current machine type
to file in file
-enable-sync-profile
Enable synchronization profiling.
-perfmap
Generate a map file for Linux perf tools that will allow basic
profiling information to be broken down into basic blocks.
-jitdump
Generate a dump file for Linux perf tools that maps basic blocks
to symbol names, line numbers and JITted code.
Generic object creation
-object typename[,prop1=value1,...]
Create a new object of type typename setting properties in the
order they are specified. Note that the 'id' property must be
set. These objects are placed in the '/objects' path.
-object
memory-backend-file,id=id,size=size,mem-path=dir,share=on|off,discard-data=on|off,merge=on|off,dump=on|off,prealloc=on|off,host-nodes=host-nodes,policy=default|preferred|bind|interleave,align=align,offset=offset,readonly=on|off,rom=on|off|auto
Creates a memory file backend object, which can be used
to back the guest RAM with huge pages.
The id parameter is a unique ID that will be used to
reference this memory region in other parameters, e.g.
-numa, -device nvdimm, etc.
The size option provides the size of the memory region,
and accepts common suffixes, e.g. 500M.
The mem-path provides the path to either a shared memory
or huge page filesystem mount.
The share boolean option determines whether the memory
region is marked as private to QEMU, or shared. The
latter allows a co-operating external process to access
the QEMU memory region.
Setting share=on might affect the ability to configure
NUMA bindings for the memory backend under some
circumstances, see
Documentation/vm/numa_memory_policy.txt on the Linux
kernel source tree for additional details.
Setting the discard-data boolean option to on indicates
that file contents can be destroyed when QEMU exits, to
avoid unnecessarily flushing data to the backing file.
Note that discard-data is only an optimization, and QEMU
might not discard file contents if it aborts unexpectedly
or is terminated using SIGKILL.
The merge boolean option enables memory merge, also known
as MADV_MERGEABLE, so that Kernel Samepage Merging will
consider the pages for memory deduplication.
Setting the dump boolean option to off excludes the
memory from core dumps. This feature is also known as
MADV_DONTDUMP.
The prealloc boolean option enables memory preallocation.
The host-nodes option binds the memory range to a list of
NUMA host nodes.
The policy option sets the NUMA policy to one of the
following values:
default
default host policy
preferred
prefer the given host node list for allocation
bind restrict memory allocation to the given host node
list
interleave
interleave memory allocations across the given
host node list
The align option specifies the base address alignment
when QEMU mmap(2) mem-path, and accepts common suffixes,
eg 2M. Some backend store specified by mem-path requires
an alignment different than the default one used by QEMU,
eg the device DAX /dev/dax0.0 requires 2M alignment
rather than 4K. In such cases, users can specify the
required alignment via this option.
The offset option specifies the offset into the target
file that the region starts at. You can use this
parameter to back multiple regions with a single file.
The pmem option specifies whether the backing file
specified by mem-path is in host persistent memory that
can be accessed using the SNIA NVM programming model
(e.g. Intel NVDIMM). If pmem is set to 'on', QEMU will
take necessary operations to guarantee the persistence of
its own writes to mem-path (e.g. in vNVDIMM label
emulation and live migration). Also, we will map the
backend-file with MAP_SYNC flag, which ensures the file
metadata is in sync for mem-path in case of host crash or
a power failure. MAP_SYNC requires support from both the
host kernel (since Linux kernel 4.15) and the filesystem
of mem-path mounted with DAX option.
The readonly option specifies whether the backing file is
opened read-only or read-write (default).
The rom option specifies whether to create Read Only
Memory (ROM) that cannot be modified by the VM. Any write
attempts to such ROM will be denied. Most use cases want
proper RAM instead of ROM. However, selected use cases,
like R/O NVDIMMs, can benefit from ROM. If set to on,
create ROM; if set to off, create writable RAM; if set to
auto (default), the value of the readonly option is used.
This option is primarily helpful when we want to have
writable RAM in configurations that would traditionally
create ROM before the rom option was introduced: VM
templating, where we want to open a file readonly
(readonly=on) and mark the memory to be private for QEMU
(share=off). For this use case, we need writable RAM
instead of ROM, and want to also set rom=off.
-object
memory-backend-ram,id=id,merge=on|off,dump=on|off,share=on|off,prealloc=on|off,size=size,host-nodes=host-nodes,policy=default|preferred|bind|interleave
Creates a memory backend object, which can be used to
back the guest RAM. Memory backend objects offer more
control than the -m option that is traditionally used to
define guest RAM. Please refer to memory-backend-file
for a description of the options.
-object
memory-backend-memfd,id=id,merge=on|off,dump=on|off,share=on|off,prealloc=on|off,size=size,host-nodes=host-nodes,policy=default|preferred|bind|interleave,seal=on|off,hugetlb=on|off,hugetlbsize=size
Creates an anonymous memory file backend object, which
allows QEMU to share the memory with an external process
(e.g. when using vhost-user). The memory is allocated
with memfd and optional sealing. (Linux only)
The seal option creates a sealed-file, that will block
further resizing the memory ('on' by default).
The hugetlb option specify the file to be created resides
in the hugetlbfs filesystem (since Linux 4.14). Used in
conjunction with the hugetlb option, the hugetlbsize
option specify the hugetlb page size on systems that
support multiple hugetlb page sizes (it must be a power
of 2 value supported by the system).
In some versions of Linux, the hugetlb option is
incompatible with the seal option (requires at least
Linux 4.16).
Please refer to memory-backend-file for a description of
the other options.
The share boolean option is on by default with memfd.
-object
memory-backend-shm,id=id,merge=on|off,dump=on|off,share=on|off,prealloc=on|off,size=size,host-nodes=host-nodes,policy=default|preferred|bind|interleave
Creates a POSIX shared memory backend object, which
allows QEMU to share the memory with an external process
(e.g. when using vhost-user).
memory-backend-shm is a more portable and less featureful
version of memory-backend-memfd. It can then be used in
any POSIX system, especially when memfd is not supported.
Please refer to memory-backend-file for a description of
the options.
The share boolean option is on by default with shm.
Setting it to off will cause a failure during allocation
because it is not supported by this backend.
-object iommufd,id=id[,fd=fd]
Creates an iommufd backend which allows control of DMA
mapping through the /dev/iommu device.
The id parameter is a unique ID which frontends (such as
vfio-pci of vdpa) will use to connect with the iommufd
backend.
The fd parameter is an optional pre-opened file
descriptor resulting from /dev/iommu opening. Usually the
iommufd is shared across all subsystems, bringing the
benefit of centralized reference counting.
-object rng-builtin,id=id
Creates a random number generator backend which obtains
entropy from QEMU builtin functions. The id parameter is
a unique ID that will be used to reference this entropy
backend from the virtio-rng device. By default, the
virtio-rng device uses this RNG backend.
-object rng-random,id=id,filename=/dev/random
Creates a random number generator backend which obtains
entropy from a device on the host. The id parameter is a
unique ID that will be used to reference this entropy
backend from the virtio-rng device. The filename
parameter specifies which file to obtain entropy from and
if omitted defaults to /dev/urandom.
-object rng-egd,id=id,chardev=chardevid
Creates a random number generator backend which obtains
entropy from an external daemon running on the host. The
id parameter is a unique ID that will be used to
reference this entropy backend from the virtio-rng
device. The chardev parameter is the unique ID of a
character device backend that provides the connection to
the RNG daemon.
-object
tls-creds-anon,id=id,endpoint=endpoint,dir=/path/to/cred/dir,verify-peer=on|off
Creates a TLS anonymous credentials object, which can be
used to provide TLS support on network backends. The id
parameter is a unique ID which network backends will use
to access the credentials. The endpoint is either server
or client depending on whether the QEMU network backend
that uses the credentials will be acting as a client or
as a server. If verify-peer is enabled (the default) then
once the handshake is completed, the peer credentials
will be verified, though this is a no-op for anonymous
credentials.
The dir parameter tells QEMU where to find the credential
files. For server endpoints, this directory may contain
a file dh-params.pem providing diffie-hellman parameters
to use for the TLS server. If the file is missing, QEMU
will generate a set of DH parameters at startup. This is
a computationally expensive operation that consumes
random pool entropy, so it is recommended that a
persistent set of parameters be generated upfront and
saved.
-object
tls-creds-psk,id=id,endpoint=endpoint,dir=/path/to/keys/dir[,username=username]
Creates a TLS Pre-Shared Keys (PSK) credentials object,
which can be used to provide TLS support on network
backends. The id parameter is a unique ID which network
backends will use to access the credentials. The endpoint
is either server or client depending on whether the QEMU
network backend that uses the credentials will be acting
as a client or as a server. For clients only, username
is the username which will be sent to the server. If
omitted it defaults to "qemu".
The dir parameter tells QEMU where to find the keys file.
It is called "dir/keys.psk" and contains "username:key"
pairs. This file can most easily be created using the
GnuTLS psktool program.
For server endpoints, dir may also contain a file
dh-params.pem providing diffie-hellman parameters to use
for the TLS server. If the file is missing, QEMU will
generate a set of DH parameters at startup. This is a
computationally expensive operation that consumes random
pool entropy, so it is recommended that a persistent set
of parameters be generated up front and saved.
-object
tls-creds-x509,id=id,endpoint=endpoint,dir=/path/to/cred/dir,priority=priority,verify-peer=on|off,passwordid=id
Creates a TLS anonymous credentials object, which can be
used to provide TLS support on network backends. The id
parameter is a unique ID which network backends will use
to access the credentials. The endpoint is either server
or client depending on whether the QEMU network backend
that uses the credentials will be acting as a client or
as a server. If verify-peer is enabled (the default) then
once the handshake is completed, the peer credentials
will be verified. With x509 certificates, this implies
that the clients must be provided with valid client
certificates too.
The dir parameter tells QEMU where to find the credential
files. For server endpoints, this directory may contain
a file dh-params.pem providing diffie-hellman parameters
to use for the TLS server. If the file is missing, QEMU
will generate a set of DH parameters at startup. This is
a computationally expensive operation that consumes
random pool entropy, so it is recommended that a
persistent set of parameters be generated upfront and
saved.
For x509 certificate credentials the directory will
contain further files providing the x509 certificates.
The certificates must be stored in PEM format, in
filenames ca-cert.pem, ca-crl.pem (optional),
server-cert.pem (only servers), server-key.pem (only
servers), client-cert.pem (only clients), and
client-key.pem (only clients).
For the server-key.pem and client-key.pem files which
contain sensitive private keys, it is possible to use an
encrypted version by providing the passwordid parameter.
This provides the ID of a previously created secret
object containing the password for decryption.
The priority parameter allows to override the global
default priority used by gnutls. This can be useful if
the system administrator needs to use a weaker set of
crypto priorities for QEMU without potentially forcing
the weakness onto all applications. Or conversely if one
wants wants a stronger default for QEMU than for all
other applications, they can do this through this
parameter. Its format is a gnutls priority string as
described at .
-object tls-cipher-suites,id=id,priority=priority
Creates a TLS cipher suites object, which can be used to
control the TLS cipher/protocol algorithms that
applications are permitted to use.
The id parameter is a unique ID which frontends will use
to access the ordered list of permitted TLS cipher suites
from the host.
The priority parameter allows to override the global
default priority used by gnutls. This can be useful if
the system administrator needs to use a weaker set of
crypto priorities for QEMU without potentially forcing
the weakness onto all applications. Or conversely if one
wants wants a stronger default for QEMU than for all
other applications, they can do this through this
parameter. Its format is a gnutls priority string as
described at .
An example of use of this object is to control UEFI HTTPS
Boot. The tls-cipher-suites object exposes the ordered
list of permitted TLS cipher suites from the host side to
the guest firmware, via fw_cfg. The list is represented
as an array of IANA_TLS_CIPHER objects. The firmware uses
the IANA_TLS_CIPHER array for configuring guest-side TLS.
In the following example, the priority at which the
host-side policy is retrieved is given by the priority
property. Given that QEMU uses GNUTLS, priority=@SYSTEM
may be used to refer to
/etc/crypto-policies/back-ends/gnutls.config.
# qemu-system-x86_64 \
-object tls-cipher-suites,id=mysuite0,priority=@SYSTEM \
-fw_cfg name=etc/edk2/https/ciphers,gen_id=mysuite0
-object
filter-buffer,id=id,netdev=netdevid,interval=t[,queue=all|rx|tx][,status=on|off][,position=head|tail|id=][,insert=behind|before]
Interval t can't be 0, this filter batches the packet
delivery: all packets arriving in a given interval on
netdev netdevid are delayed until the end of the
interval. Interval is in microseconds. status is optional
that indicate whether the netfilter is on (enabled) or
off (disabled), the default status for netfilter will be
'on'.
queue all|rx|tx is an option that can be applied to any
netfilter.
all: the filter is attached both to the receive and the
transmit queue of the netdev (default).
rx: the filter is attached to the receive queue of the
netdev, where it will receive packets sent to the netdev.
tx: the filter is attached to the transmit queue of the
netdev, where it will receive packets sent by the netdev.
position head|tail|id= is an option to specify where
the filter should be inserted in the filter list. It can
be applied to any netfilter.
head: the filter is inserted at the head of the filter
list, before any existing filters.
tail: the filter is inserted at the tail of the filter
list, behind any existing filters (default).
id=: the filter is inserted before or behind the
filter specified by , see the insert option below.
insert behind|before is an option to specify where to
insert the new filter relative to the one specified with
position=id=. It can be applied to any netfilter.
before: insert before the specified filter.
behind: insert behind the specified filter (default).
-object
filter-mirror,id=id,netdev=netdevid,outdev=chardevid,queue=all|rx|tx[,vnet_hdr_support][,position=head|tail|id=][,insert=behind|before]
filter-mirror on netdev netdevid,mirror net packet to
chardevchardevid, if it has the vnet_hdr_support flag,
filter-mirror will mirror packet with vnet_hdr_len.
-object
filter-redirector,id=id,netdev=netdevid,indev=chardevid,outdev=chardevid,queue=all|rx|tx[,vnet_hdr_support][,position=head|tail|id=][,insert=behind|before]
filter-redirector on netdev netdevid,redirect filter's
net packet to chardev chardevid,and redirect indev's
packet to filter.if it has the vnet_hdr_support flag,
filter-redirector will redirect packet with vnet_hdr_len.
Create a filter-redirector we need to differ outdev id
from indev id, id can not be the same. we can just use
indev or outdev, but at least one of indev or outdev need
to be specified.
-object
filter-rewriter,id=id,netdev=netdevid,queue=all|rx|tx,[vnet_hdr_support][,position=head|tail|id=][,insert=behind|before]
Filter-rewriter is a part of COLO project.It will rewrite
tcp packet to secondary from primary to keep secondary
tcp connection,and rewrite tcp packet to primary from
secondary make tcp packet can be handled by client.if it
has the vnet_hdr_support flag, we can parse packet with
vnet header.
usage: colo secondary: -object
filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0
-object
filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1
-object filter-rewriter,id=rew0,netdev=hn0,queue=all
-object
filter-dump,id=id,netdev=dev[,file=filename][,maxlen=len][,position=head|tail|id=][,insert=behind|before]
Dump the network traffic on netdev dev to the file
specified by filename. At most len bytes (64k by default)
per packet are stored. The file format is libpcap, so it
can be analyzed with tools such as tcpdump or Wireshark.
-object
colo-compare,id=,primary_in=,secondary_in=,outdev=,iothread=[,vnet_hdr_support][,notify_dev=][,compare_timeout=][,expired_scan_cycle=][,max_queue_size=]
Colo-compare gets packets from the chardev backends
specified by primary_in and secondary_in, and compares
whether the payloads of the primary packet and the
secondary packet are the same. If they match, it will
output the primary packet to the chardev backend
specified by outdev; otherwise it will notify
COLO-framework to do a checkpoint and send the primary
packet to outdev.
In order to improve efficiency, we need to put the task
of comparison in another iothread; the iothread option
specifies that iothread object (which your commandline
should create).
The vnet_hdr_support flag tells colo compare to pass the
vnet header length when it sends and receives packets.
The compare_timeout option sets the maximum time that
colo-compare will hold the packet for, in ms.
The expired_scan_cycle option sets the period of scanning
expired primary node network packets, in ms.
The max_queue_size option sets the max compare queue
size.
If you want to use Xen COLO, you need to specify
notify_dev to tell colo-compare how to notify Xen
colo-frame to do a checkpoint.
COLO-compare must be used with the help of filter-mirror,
filter-redirector and filter-rewriter.
KVM COLO
primary:
-netdev tap,id=hn0,vhost=off
-device e1000,id=e0,netdev=hn0,mac=52:a4:00:12:78:66
-chardev socket,id=mirror0,host=3.3.3.3,port=9003,server=on,wait=off
-chardev socket,id=compare1,host=3.3.3.3,port=9004,server=on,wait=off
-chardev socket,id=compare0,host=3.3.3.3,port=9001,server=on,wait=off
-chardev socket,id=compare0-0,host=3.3.3.3,port=9001
-chardev socket,id=compare_out,host=3.3.3.3,port=9005,server=on,wait=off
-chardev socket,id=compare_out0,host=3.3.3.3,port=9005
-object iothread,id=iothread1
-object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0
-object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out
-object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0
-object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0,iothread=iothread1
secondary:
-netdev tap,id=hn0,vhost=off
-device e1000,netdev=hn0,mac=52:a4:00:12:78:66
-chardev socket,id=red0,host=3.3.3.3,port=9003
-chardev socket,id=red1,host=3.3.3.3,port=9004
-object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0
-object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1
Xen COLO
primary:
-netdev tap,id=hn0,vhost=off
-device e1000,id=e0,netdev=hn0,mac=52:a4:00:12:78:66
-chardev socket,id=mirror0,host=3.3.3.3,port=9003,server=on,wait=off
-chardev socket,id=compare1,host=3.3.3.3,port=9004,server=on,wait=off
-chardev socket,id=compare0,host=3.3.3.3,port=9001,server=on,wait=off
-chardev socket,id=compare0-0,host=3.3.3.3,port=9001
-chardev socket,id=compare_out,host=3.3.3.3,port=9005,server=on,wait=off
-chardev socket,id=compare_out0,host=3.3.3.3,port=9005
-chardev socket,id=notify_way,host=3.3.3.3,port=9009,server=on,wait=off
-object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0
-object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out
-object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0
-object iothread,id=iothread1
-object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0,notify_dev=notify_way,iothread=iothread1
secondary:
-netdev tap,id=hn0,vhost=off
-device e1000,netdev=hn0,mac=52:a4:00:12:78:66
-chardev socket,id=red0,host=3.3.3.3,port=9003
-chardev socket,id=red1,host=3.3.3.3,port=9004
-object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0
-object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1
If you want to know the detail of above command line, you
can read the colo-compare git log.
-object cryptodev-backend-builtin,id=id[,queues=queues]
Creates a cryptodev backend which executes crypto
operations from the QEMU cipher APIs. The id parameter is
a unique ID that will be used to reference this cryptodev
backend from the virtio-crypto device. The queues
parameter is optional, which specify the queue number of
cryptodev backend, the default of queues is 1.
# qemu-system-x86_64 \
[...] \
-object cryptodev-backend-builtin,id=cryptodev0 \
-device virtio-crypto-pci,id=crypto0,cryptodev=cryptodev0 \
[...]
-object
cryptodev-vhost-user,id=id,chardev=chardevid[,queues=queues]
Creates a vhost-user cryptodev backend, backed by a
chardev chardevid. The id parameter is a unique ID that
will be used to reference this cryptodev backend from the
virtio-crypto device. The chardev should be a unix domain
socket backed one. The vhost-user uses a specifically
defined protocol to pass vhost ioctl replacement messages
to an application on the other end of the socket. The
queues parameter is optional, which specify the queue
number of cryptodev backend for multiqueue vhost-user,
the default of queues is 1.
# qemu-system-x86_64 \
[...] \
-chardev socket,id=chardev0,path=/path/to/socket \
-object cryptodev-vhost-user,id=cryptodev0,chardev=chardev0 \
-device virtio-crypto-pci,id=crypto0,cryptodev=cryptodev0 \
[...]
-object
secret,id=id,data=string,format=raw|base64[,keyid=secretid,iv=string]
-object
secret,id=id,file=filename,format=raw|base64[,keyid=secretid,iv=string]
Defines a secret to store a password, encryption key, or
some other sensitive data. The sensitive data can either
be passed directly via the data parameter, or indirectly
via the file parameter. Using the data parameter is
insecure unless the sensitive data is encrypted.
The sensitive data can be provided in raw format (the
default), or base64. When encoded as JSON, the raw format
only supports valid UTF-8 characters, so base64 is
recommended for sending binary data. QEMU will convert
from which ever format is provided to the format it needs
internally. eg, an RBD password can be provided in raw
format, even though it will be base64 encoded when passed
onto the RBD sever.
For added protection, it is possible to encrypt the data
associated with a secret using the AES-256-CBC cipher.
Use of encryption is indicated by providing the keyid and
iv parameters. The keyid parameter provides the ID of a
previously defined secret that contains the AES-256
decryption key. This key should be 32-bytes long and be
base64 encoded. The iv parameter provides the random
initialization vector used for encryption of this
particular secret and should be a base64 encrypted string
of the 16-byte IV.
The simplest (insecure) usage is to provide the secret
inline
# qemu-system-x86_64 -object secret,id=sec0,data=letmein,format=raw
The simplest secure usage is to provide the secret via a
file
# printf "letmein" > mypasswd.txt # QEMU_SYSTEM_MACRO
-object secret,id=sec0,file=mypasswd.txt,format=raw
For greater security, AES-256-CBC should be used. To
illustrate usage, consider the openssl command line tool
which can encrypt the data. Note that when encrypting,
the plaintext must be padded to the cipher block size (32
bytes) using the standard PKCS#5/6 compatible padding
algorithm.
First a master key needs to be created in base64
encoding:
# openssl rand -base64 32 > key.b64
# KEY=$(base64 -d key.b64 | hexdump -v -e '/1 "%02X"')
Each secret to be encrypted needs to have a random
initialization vector generated. These do not need to be
kept secret
# openssl rand -base64 16 > iv.b64
# IV=$(base64 -d iv.b64 | hexdump -v -e '/1 "%02X"')
The secret to be defined can now be encrypted, in this
case we're telling openssl to base64 encode the result,
but it could be left as raw bytes if desired.
# SECRET=$(printf "letmein" |
openssl enc -aes-256-cbc -a -K $KEY -iv $IV)
When launching QEMU, create a master secret pointing to
key.b64 and specify that to be used to decrypt the user
password. Pass the contents of iv.b64 to the second
secret
# qemu-system-x86_64 \
-object secret,id=secmaster0,format=base64,file=key.b64 \
-object secret,id=sec0,keyid=secmaster0,format=base64,\
data=$SECRET,iv=$([:]//"
By default qemu will use the iSCSI initiator-name
'iqn.2008-11.org.linux-kvm[:]' but this can also be set
from the command line or a configuration file.
Since version QEMU 2.4 it is possible to specify a iSCSI request
timeout to detect stalled requests and force a reestablishment
of the session. The timeout is specified in seconds. The default
is 0 which means no timeout. Libiscsi 1.15.0 or greater is
required for this feature.
Example (without authentication):
qemu-system-x86_64 -iscsi initiator-name=iqn.2001-04.com.example:my-initiator \
-cdrom iscsi://192.0.2.1/iqn.2001-04.com.example/2 \
-drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1
Example (CHAP username/password via URL):
qemu-system-x86_64 -drive file=iscsi://user%password@192.0.2.1/iqn.2001-04.com.example/1
Example (CHAP username/password via environment variables):
LIBISCSI_CHAP_USERNAME="user" \
LIBISCSI_CHAP_PASSWORD="password" \
qemu-system-x86_64 -drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1
NBD QEMU supports NBD (Network Block Devices) both using TCP
protocol as well as Unix Domain Sockets. With TCP, the default
port is 10809.
Syntax for specifying a NBD device using TCP, in preferred URI
form: "nbd://[:]/[]"
Syntax for specifying a NBD device using Unix Domain Sockets;
remember that '?' is a shell glob character and may need
quoting: "nbd+unix:///[]?socket="
Older syntax that is also recognized:
"nbd::[:exportname=]"
Syntax for specifying a NBD device using Unix Domain Sockets
"nbd:unix:[:exportname=]"
Example for TCP
qemu-system-x86_64 --drive file=nbd:192.0.2.1:30000
Example for Unix Domain Sockets
qemu-system-x86_64 --drive file=nbd:unix:/tmp/nbd-socket
SSH QEMU supports SSH (Secure Shell) access to remote disks.
Examples:
qemu-system-x86_64 -drive file=ssh://user@host/path/to/disk.img
qemu-system-x86_64 -drive file.driver=ssh,file.user=user,file.host=host,file.port=22,file.path=/path/to/disk.img
Currently authentication must be done using ssh-agent. Other
authentication methods may be supported in future.
GlusterFS
GlusterFS is a user space distributed file system. QEMU supports
the use of GlusterFS volumes for hosting VM disk images using
TCP and Unix Domain Sockets transport protocols.
Syntax for specifying a VM disk image on GlusterFS volume is
URI:
gluster[+type]://[host[:port]]/volume/path[?socket=...][,debug=N][,logfile=...]
JSON:
'json:{"driver":"qcow2","file":{"driver":"gluster","volume":"testvol","path":"a.img","debug":N,"logfile":"...",
"server":[{"type":"tcp","host":"...","port":"..."},
{"type":"unix","socket":"..."}]}}'
Example
URI:
qemu-system-x86_64 --drive file=gluster://192.0.2.1/testvol/a.img,
file.debug=9,file.logfile=/var/log/qemu-gluster.log
JSON:
qemu-system-x86_64 'json:{"driver":"qcow2",
"file":{"driver":"gluster",
"volume":"testvol","path":"a.img",
"debug":9,"logfile":"/var/log/qemu-gluster.log",
"server":[{"type":"tcp","host":"1.2.3.4","port":24007},
{"type":"unix","socket":"/var/run/glusterd.socket"}]}}'
qemu-system-x86_64 -drive driver=qcow2,file.driver=gluster,file.volume=testvol,file.path=/path/a.img,
file.debug=9,file.logfile=/var/log/qemu-gluster.log,
file.server.0.type=tcp,file.server.0.host=1.2.3.4,file.server.0.port=24007,
file.server.1.type=unix,file.server.1.socket=/var/run/glusterd.socket
See also .
HTTP/HTTPS/FTP/FTPS
QEMU supports read-only access to files accessed over http(s)
and ftp(s).
Syntax using a single filename:
://[[:]@]/
where:
protocol
'http', 'https', 'ftp', or 'ftps'.
username
Optional username for authentication to the remote
server.
password
Optional password for authentication to the remote
server.
host Address of the remote server.
path Path on the remote server, including any query string.
The following options are also supported:
url The full URL when passing options to the driver
explicitly.
readahead
The amount of data to read ahead with each range request
to the remote server. This value may optionally have the
suffix 'T', 'G', 'M', 'K', 'k' or 'b'. If it does not
have a suffix, it will be assumed to be in bytes. The
value must be a multiple of 512 bytes. It defaults to
256k.
sslverify
Whether to verify the remote server's certificate when
connecting over SSL. It can have the value 'on' or 'off'.
It defaults to 'on'.
cookie Send this cookie (it can also be a list of cookies
separated by ';') with each outgoing request. Only
supported when using protocols such as HTTP which support
cookies, otherwise ignored.
timeout
Set the timeout in seconds of the CURL connection. This
timeout is the time that CURL waits for a response from
the remote server to get the size of the image to be
downloaded. If not set, the default timeout of 5 seconds
is used.
force-range
Don't issue a HEAD HTTP request to discover if the http
server server supports range requests and rely only on
GET requests. This is especially useful for S3 presigned
URLs where HEAD requests are unauthorized. It defaults to
'false'.
Note that when passing options to qemu explicitly, driver is the
value of .
Example: boot from a remote Fedora 20 live ISO image
qemu-system-x86_64 --drive media=cdrom,file=https://archives.fedoraproject.org/pub/archive/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly
qemu-system-x86_64 --drive media=cdrom,file.driver=http,file.url=http://archives.fedoraproject.org/pub/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly
Example: boot from a remote Fedora 20 cloud image using a local
overlay for writes, copy-on-read, and a readahead of 64k
qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"http",, "file.url":"",, "file.readahead":"64k"}' /tmp/Fedora-x86_64-20-20131211.1-sda.qcow2
qemu-system-x86_64 -drive file=/tmp/Fedora-x86_64-20-20131211.1-sda.qcow2,copy-on-read=on
Example: boot from an image stored on a VMware vSphere server
with a self-signed certificate using a local overlay for writes,
a readahead of 64k and a timeout of 10 seconds.
qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"https",, "file.url":"",, "file.sslverify":"off",, "file.readahead":"64k",, "file.timeout":10}' /tmp/test.qcow2
qemu-system-x86_64 -drive file=/tmp/test.qcow2
SEE ALSO
The HTML documentation of QEMU for more precise information and Linux
user mode emulator invocation.
Author
Fabrice Bellard
Copyright
2026, The QEMU Project Developers
11.0.2 July 9, 2026 QEMU(1)