mkinitcpio - Create an initial ramdisk environment
Creates an initial ramdisk environment for booting the linux kernel. The initial
ramdisk is in essence a very small environment (early userspace) which loads
various kernel modules and sets up necessary things before handing over
control to init. This makes it possible to have, for example, encrypted root
filesystems and root filesystems on a software RAID array. mkinitcpio allows
for easy extension with custom hooks, has autodetection at runtime, and many
-A, --addhooks hooks
Add the additional hooks to the image. These will
be processed in order after all other hooks from the config file. Multiple
hooks should be comma-separated. This option can be specified multiple
-c, --config config
Use config file to generate the ramdisk. Default:
-d, --generatedir directory
Set directory as the location where the initramfs
is built. This might be useful to generate a shutdown ramfs in
-D, --hookdir directory
Set directory as the location where hooks will be
searched for when generating the image.
-g, --generate filename
Generate a CPIO image as filename. Default: no;
this means nothing will be written to the filesystem unless this option is
-H, --hookhelp hookname
Output help for hookname hookname.
Output a short overview of available command-line
-k, --kernel kernelversion
Use kernelversion, instead of the current running
kernel. This may be a path to a kernel image (only supported for x86-based
architectures), a specific kernel version or the special keyword none.
In the latter case, no kernel modules are added to the image.
List all available hooks.
Display modules found via autodetection. mkinitcpio will
automatically try to determine which kernel modules are needed to start your
computer. This option lists which modules were detected.
Disable color output.
Process all presets contained in
/etc/mkinitcpio.d. See the -p option for more detail about
-p, --preset preset
Build initramfs image(s) according to specified
preset. This may be a file in /etc/mkinitcpio.d (without the .preset
extension) or a full, absolute path to a file. This option may be specified
multiple times to process multiple presets.
-r, --moduleroot root
Specifies the root directory to find modules in,
defaulting to /.
-S, --skiphooks hooks
Skip hooks when generating the image. Multiple
hooks should be comma-separated. This option can be specified multiple
Saves the build directory for the initial ramdisk.
Default: no; This means the directory will not be retained if this option
isn’t specified. Useful for debugging purposes.
-t, --builddir tmpdir
Use tmpdir as the temporary build directory
instead of /tmp. tmpdir must exist. The TMPDIR environment
variable is also honored to set this location, but the command line option
will take precedence.
Display version information.
Verbose output. Outputs more information about
what’s happening during creation of the ramdisk.
-z, --compress compress
Override the compression method with the compress
A preset is a pre-defined definition on how to create an initial ramdisk.
Instead of specifying the configuration file and which output file, every time
you generate a new initial ramdisk, you define a preset and use the -p switch
to generate an initial ramdisk according to your preset. Presets are located
Install hooks are bash scripts which are sourced during mkinitcpio runtime in
order to add modules, binaries, and other files to the image. A variety of
functions exist to facilitate this.
Adds the module specified by modname to the image.
Dependencies are derived and added automatically.
add_binary binary [ destination ] [
Adds a binary to the image. The argument binary
need not be an absolute path and, if needed, a lookup will be performed. If
the binary is a dynamically linked ELF binary, dependencies will be
automatically added. Optionally, a destination within the initramfs image as
well as a file mode can be specified. By default, the destintation and mode be
taken from the source derived from binary.
add_file path [ destination ] [ mode
Adds a file and any needed parent directories to the
image. Optionally, a destination within the initramfs image as well as a file
mode can be specified. By default, the destination and mode will be taken from
the source and mode of the file specified by the path.
Adds a directory and its parents to the image.
add_full_dir directory [ glob ] [
Recursively adds a directory to the image by walking the
given path and calling add_file
, and add_symlink
accordingly. This function will not follow symlinks, nor will it add the
targets of symlinks.
If the 'glob' argument is passed, only files and symlinks matching this glob
will be added.
If the 'strip_prefix' argument is passed, it will be used to strip the
destination path (path in the initramfs image) from the prefix specified by
the 'strip_prefix' argument. This can be useful when writing rootfs-overlay
add_symlink path [ link-target ]
Adds a symlink to the image at the specified path,
optionally pointing to the specified link-target. If the link-target is not
provided, it is assumed that this symlink exists in the real filesystem, and
the target will be read using readlink. There is no checking done to ensure
that the target of the symlink exists, and symlinks will not be followed
add_all_modules [ -f filter ] pattern
Adds modules to the image, without regard for the
autodetect whitelist. pattern should be a subdirectory within the
kernel tree describing a subset of modules to be included. Further refinement
can be provided via the -f flag with an extended regular expression.
add_checked_modules [ -f filter ] pattern
Similar to add_all_modules with the constraint
that only modules matching the whitelist generated by the autodetect hook will
be added to the image. If the autodetect hook is not present in the image,
this function is identical to add_all_modules.
Adds a runtime hook to the image, which is a busybox ash
compatible shell script. The name of the script is guaranteed to match the
name of the hook the script is called from.
Runtime hooks added to the image via the add_runscript function from an
install hook are able to provide extra functionality during early userspace.
Specific functions in these files will run at different times. A hook can
define one or more of these. At each hook point, hooks are run in the order
that they are defined in the HOOKS variable, except for cleanup hooks which
are run in reverse.
Functions of this name will be run once the API mounts
have been setup and the kernel command line has been parsed. Daemons needed
for early userspace should be started from this hook point.
Functions of this name will be run after any early hooks,
and after user defined modules have been installed. This is the most common
hook point, and functionality such as scanning for LVM volumes and mapping
encrypted volumes should be performed here.
Functions of this name will be run after root has been
mounted. This is generally used for further necessary setup in the real root,
such as mounting other system partitions.
Functions of this name are run as late as possible. Any
daemons started from a run_earlyhook function should be shut down here in
preparation for switching to the real root.
mkinitcpio gives special treatment to certain environment variables passed on
the kernel command line:
If specified, mkinitcpio will start a shell during early
init. The optional parameter controls when this occurs: when premount
or no parameter are specified, the shell will be launched prior to mounting
root. If postmount is specified, the shell will be launched after
This is a comma separated list of hooks which will be
skipped during early init.
This is a comma separated list of modules which will be
loaded prior to any others. This is generally not needed, and usually points
to a configuration or kernel problem.
Causes mkinitcpio to output fewer messages during boot.
Errors will not be suppressed.
Specifies that root should be mounted with readonly
permissions. This is the default behavior.
Specifies that root should be mounted with readwrite
permissions. This is generally only useful if your initramfs uses the
This variable describes the root partition which early
init will mount before passing control to the real init. mkinitcpio
understands a variety of formats, the most basic of which is the path to the
block device, either directly such as /dev/sda2, or using a udev
symlink such as /dev/disk/by-label/CorsairF80-root. Support for
identification by LABEL or UUID tags are also supported, such as,
LABEL=CorsairF80-root. As of util-linux 2.22, PARTUUID and PARTLABEL
are also supported. Identification via hex encoded major/minor device ID is
supported for legacy reasons, but should be avoided as it tends to be
Sets the delay, in seconds, that mkinitcpio is willing to
wait for the root device to show up, if it is not available immediately. This
defaults to 10 seconds. If an invalid integer is passed, this variable will
have no effect.
A comma-separated list of flags which will be passed onto
command when mounting the root filesystem. Acceptable
values are filesystem specific.
Overrides the type of filesystem being mounted as root.
This should almost never be needed as mount(8)
usually detects this on
Enables shell debug (xtrace). If rd.log is not
also a parameter on the kernel command line, this parameter implies
Enables logging of early userspace messages. If
specified, the optional parameter describes where this information is logged.
Multiple options can be OR’d together using the pipe (|) character.
Messages are always logged to the console unless the quiet
passed. If the optional parameter is not specified, kmsg|console
assumed. If rd.log
is not present on the kernel command line, no
logging will take place.
Writes output to /dev/console.
Writes output to /run/initramfs/init.log.
Writes output to the /dev/kmsg device (introduced
in Linux 3.5). This option is a no-op if your kernel lacks support for
Writes output to all known log targets.
These are only the variables that the core of mkinitcpio honor.
Additional hooks may look for other environment variables and should be
documented by the help output for the hook.
mkinitcpio aims to create reproducible initramfs images by default.
This means that two subsequent runs of mkinitcpio should produce
two files that are identical at the binary level.
Timestamps within the initramfs are set to the Unix epoch of
Note that in order for the build to be fully reproducible, the
compressor specified (e.g. gzip, xz) must also produce reproducible
archives. At the time of writing, as an inexhaustive example, the lzop
compressor is incapable of producing reproducible archives due to the
insertion of a runtime timestamp.
More information can be found at
Default configuration file for mkinitcpio.
Directory containing mkinitcpio presets.
Search path for build time hooks.
Search path for early userspace runtime hooks.
Perform a dry-run. This will generate an initial
ramdisk but will not write anything. Use -g to create the real image.
mkinitcpio -p linux
Create an initial ramdisk based on the linux
mkinitcpio -g /boot/initramfs-linux.img -k
Create an initial ramdisk for the kernel at
/boot/vmlinuz-linux. The resulting image will be written to
mkinitcpio is created and maintained by the Arch Linux Developer community.
Copyright (c) Arch Linux 2006-2021