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.\" ========================================================================
.\"
.IX Title "nbdinfo 1"
.TH nbdinfo 1 2024-05-31 libnbd-1.20.0 LIBNBD
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH NAME
nbdinfo \- display information and metadata about NBD servers and exports
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& nbdinfo [\-\-json] NBD
.Ve
.PP
\&\f(CW\*(C`NBD\*(C'\fR is an NBD URI or subprocess:
.PP
.Vb 2
\& NBD := nbd://... | nbd+unix:// (or other URI formats)
\&      | [ CMD ARGS ... ]
.Ve
.PP
.Vb 1
\& nbdinfo \-\-size [\-\-json] NBD
.Ve
.PP
.Vb 1
\& nbdinfo \-\-uri [\-\-json] NBD
.Ve
.PP
.Vb 2
\& nbdinfo \-\-is read\-only|rotational NBD
\& nbdinfo \-\-isnt read\-only|rotational NBD
.Ve
.PP
.Vb 2
\& nbdinfo \-\-can cache|connect|... NBD
\& nbdinfo \-\-cannot cache|connect|... NBD
.Ve
.PP
.Vb 1
\& nbdinfo \-\-map [\-\-totals] [\-\-json] NBD
.Ve
.PP
.Vb 1
\& nbdinfo \-L|\-\-list [\-\-json] NBD
.Ve
.PP
.Vb 1
\& nbdinfo \-\-help
.Ve
.PP
.Vb 1
\& nbdinfo \-\-version
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
nbdinfo displays information and metadata about an NBD server.
.PP
The single required parameter can be the NBD URI of the server (see
https://github.com/NetworkBlockDevice/nbd/blob/master/doc/uri.md):
.PP
.Vb 10
\& $ nbdinfo nbd://localhost
\& protocol: newstyle\-fixed without TLS, using structured packets
\& export="":
\&         export\-size: 1048576 (1M)
\&         content: data
\&         uri: nbd://localhost:10809/
\&         is_rotational: false
\&         is_read_only: false
\&         can_cache: true
\&         can_df: true
\&         can_fast_zero: true
\&         can_flush: true
\&         can_fua: true
\&         can_multi_conn: true
\&         can_trim: true
\&         can_zero: true
\&         block_size_minimum: 1
\&         block_size_preferred: 4096 (4K)
\&         block_size_maximum: 33554432 (32M)
.Ve
.PP
For an NBD server on a local Unix domain socket you would use a
command such as this (with similar output to above):
.PP
.Vb 1
\& $ nbdinfo "nbd+unix:///?socket=/tmp/unixsock"
.Ve
.PP
Or you can run the NBD server as a subprocess (see section
"Subprocess" below):
.PP
.Vb 1
\& $ nbdinfo \-\- [ qemu\-nbd \-r \-f qcow2 file.qcow2 ]
.Ve
.SS "JSON output"
.IX Subsection "JSON output"
To display the output as JSON (eg. for scripting with \fBjq\fR\|(1)) add
the \fI\-\-json\fR parameter:
.PP
.Vb 10
\& $ nbdinfo \-\-json nbd://localhost | jq .
\& {
\&   "protocol": "newstyle\-fixed",
\&   "TLS": false,
\&   "structured": true,
\&   "extended": false,
\&   "exports": [
\&     {
\&       "export\-name": "",
\&       "content": "DOS/MBR boot sector; partition 1 : ID=0xc, start\-CHS (0x3ff,254,63), end\-CHS (0x3ff,254,63), startsector 2048, 4148704 sectors",
\&       "uri": "nbd://localhost:10809/",
\&       "is_rotational": false,
\&       "is_read_only": true,
\&       "can_cache": true,
\&       "can_df": true,
\&       "can_fast_zero": false,
\&       "can_flush": false,
\&       "can_fua": false,
\&       "can_multi_conn": true,
\&       "can_trim": false,
\&       "can_zero": false,
\&       "block_size_minimum": 1,
\&       "block_size_preferred": 4096,
\&       "block_size_maximum": 33554432,
\&       "export\-size": 2125119488,
\&       "export\-size\-str": "2075312K"
\&     }
\&   ]
\& }
.Ve
.SS Size
.IX Subsection "Size"
To display only the size in bytes of the NBD export (useful for
scripting) use the \fI\-\-size\fR parameter:
.PP
.Vb 2
\& $ nbdinfo \-\-size nbd://localhost
\& 1048576
.Ve
.PP
.Vb 2
\& $ nbdinfo \-\-size [ nbdkit null 1M ]
\& 1048576
.Ve
.SS URI
.IX Subsection "URI"
To display the canonical URI:
.PP
.Vb 2
\& $ nbdinfo \-\-uri nbd://localhost
\& nbd://localhost:10809/
.Ve
.SS "Test for flags"
.IX Subsection "Test for flags"
Use one of the \fI\-\-can\fR, \fI\-\-is\fR or \fI\-\-has\fR options below to test NBD
flags.  The command does not print anything.  Instead it exits with
success (exit\ code\ 0) if true, or failure (exit\ code\ 2) if
false.  (Other exit codes indicate an error querying the flag).
.PP
\&\fI\-\-cannot\fR, \fI\-\-isnt\fR and \fI\-\-hasnt\fR negate the test.
.PP
You can use it in shell scripts like this:
.PP
.Vb 5
\& if nbdinfo \-\-is read\-only nbd://localhost ||
\&    nbdinfo \-\-cannot trim nbd://localhost
\& then
\&     error "the device must support writing and trimming"
\& fi
.Ve
.IP "nbdinfo \-\-is read-only URI" 4
.IX Item "nbdinfo --is read-only URI"
Test if the server export is read-only.
.IP "nbdinfo \-\-can write URI" 4
.IX Item "nbdinfo --can write URI"
For convenience this is the opposite of \fI\-\-is read-only\fR.
.IP "nbdinfo \-\-can read URI" 4
.IX Item "nbdinfo --can read URI"
All NBD servers must support read, so this always exits with success
(unless there is a failure connecting to the URI).
.IP "nbdinfo \-\-can connect URI" 4
.IX Item "nbdinfo --can connect URI"
Test if we can connect to the NBD URI.
.IP "nbdinfo \-\-is tls URI" 4
.IX Item "nbdinfo --is tls URI"
Test if the NBD URI connection is using TLS.
.IP "nbdinfo \-\-has structured-reply URI" 4
.IX Item "nbdinfo --has structured-reply URI"
Test if server has support for structured replies (a prerequisite
for supporting block status commands).
.IP "nbdinfo \-\-has extended-headers URI" 4
.IX Item "nbdinfo --has extended-headers URI"
Test if server supports extended headers (a prerequisite for
supporting 64\-bit commands; implies structured replies as well).
.IP "nbdinfo \-\-is rotational URI" 4
.IX Item "nbdinfo --is rotational URI"
Test if the server export is backed by something which behaves like a
rotating disk: accessing nearby blocks may be faster than random
access and requests should be sorted to improve performance.  Many
servers do not or cannot report this accurately.
.IP "nbdinfo \-\-can block-status-payload URI" 4
.IX Item "nbdinfo --can block-status-payload URI"
Test if the server export has support for passing a client payload to
limit the response to a block status command.
.IP "nbdinfo \-\-can cache URI" 4
.IX Item "nbdinfo --can cache URI"
.PD 0
.IP "nbdinfo \-\-can df URI" 4
.IX Item "nbdinfo --can df URI"
.IP "nbdinfo \-\-can fast-zero URI" 4
.IX Item "nbdinfo --can fast-zero URI"
.IP "nbdinfo \-\-can flush URI" 4
.IX Item "nbdinfo --can flush URI"
.IP "nbdinfo \-\-can fua URI" 4
.IX Item "nbdinfo --can fua URI"
.IP "nbdinfo \-\-can multi-conn URI" 4
.IX Item "nbdinfo --can multi-conn URI"
.IP "nbdinfo \-\-can trim URI" 4
.IX Item "nbdinfo --can trim URI"
.IP "nbdinfo \-\-can zero URI" 4
.IX Item "nbdinfo --can zero URI"
.PD
Test other properties of the NBD server export.
.PP
In fact \fI\-\-can\fR/\fI\-\-is\fR/\fI\-\-has\fR, and
\&\fI\-\-cannot\fR/\fI\-\-isnt\fR/\fI\-\-hasnt\fR are synonyms, you can use them
interchangeably.
.SS Map
.IX Subsection "Map"
To show a map of which areas of the disk are allocated and sparse, use
the \fI\-\-map\fR option:
.PP
.Vb 3
\& $ nbdinfo \-\-map nbd://localhost/
\&       0  1048576  0  data
\& 1048576  1048576  3  hole,zero
.Ve
.PP
The fields are: start, size, type, description (optional).
.PP
The type field is an integer showing the raw value from the NBD
protocol.  For some maps nbdinfo knows how to translate the type into
a printable description.
.PP
To get parseable JSON output, add \fI\-\-json\fR:
.PP
.Vb 5
\& $ nbdinfo \-\-map \-\-json nbd://localhost/
\& [{ "offset": 0, "length": 1048576,
\&    "type": 0, "description": "data" },
\&  { "offset": 1048576, "length": 1048576,
\&    "type": 3, "description": "hole,zero" }]
.Ve
.PP
By default this shows the \f(CW"base:allocation"\fR map, but you can show
other maps too:
.PP
.Vb 2
\& $ nbdinfo \-\-map=qemu:dirty\-bitmap:bitmap nbd://localhost/
\& 0  1048576  1  dirty
.Ve
.PP
For more information on NBD maps, see \fIMetadata querying\fR in the NBD
protocol.
.SS "Map totals"
.IX Subsection "Map totals"
Using \fI\-\-map\ \-\-totals\fR performs the same operation as \fI\-\-map\fR but
displays a summary of the total size of each type of allocation, in
bytes and as a percentage (of the virtual size of the export).  This
is useful for estimating how much real storage is used on the server,
or might be required when copying a sparse image with \fBnbdcopy\fR\|(1).
.PP
In the example below, half (50.0%) of the disk is allocated data and
half is unallocated:
.PP
.Vb 3
\& $ nbdinfo \-\-map \-\-totals nbd://localhost/
\& 1048576  50.0%  0  data
\& 1048576  50.0%  3  hole,zero
.Ve
.PP
The fields are: total size in bytes, percentage of the virtual size,
type, description (optional).
.PP
You can also get the same information in parseable form using \fI\-\-json\fR:
.PP
.Vb 5
\& $ nbdinfo \-\-map \-\-totals \-\-json nbd://localhost/
\& [{ "size": 1048576, "percent": 50,
\&    "type": 0, "description": "data" },
\&  { "size": 1048576, "percent": 50,
\&    "type": 3, "description": "hole,zero" }]
.Ve
.PP
As with the \fI\-\-map\fR option, by default this shows the
\&\f(CW"base:allocation"\fR map, but you can show the summary for other maps.
.SS "List all exports"
.IX Subsection "List all exports"
To list all the exports available on an NBD server use the \fI\-\-list\fR
(\fI\-L\fR) option.  To get parseable JSON output, add \fI\-\-json\fR.
.PP
For example:
.PP
.Vb 10
\& $ nbdkit file dir=. \-\-run \*(Aqnbdinfo \-\-list "$uri"\*(Aq
\& protocol: newstyle\-fixed without TLS
\& export="Fedora\-Workstation\-Live\-x86_64\-29\-1.2.iso":
\&     export\-size: 1931476992 (1842M)
\&     uri: nbd://localhost:10809/Fedora\-Workstation\-Live\-x86_64\-29\-1.2.iso
\&     [...]
\& export="debian\-10.4.0\-amd64\-DVD\-1.iso":
\&     export\-size: 3955556352 (3862848K)
\&     uri: nbd://localhost:10809/debian\-10.4.0\-amd64\-DVD\-1.iso
\&     [...]
.Ve
.SS Subprocess
.IX Subsection "Subprocess"
nbdinfo can also run an NBD server as a subprocess.  This requires an
NBD server which understands systemd socket activation, such as
\&\fBqemu\-nbd\fR\|(8) or \fBnbdkit\fR\|(1).  All the usual nbdinfo modes can be
used.
.PP
For example, to give general information or display the map of a qcow2
file:
.PP
.Vb 1
\& nbdinfo \-\- [ qemu\-nbd \-r \-f qcow2 file.qcow2 ]
.Ve
.PP
.Vb 1
\& nbdinfo \-\-map \-\- [ qemu\-nbd \-r \-f qcow2 file.qcow2 ]
.Ve
.PP
Note that \f(CW\*(C`[\ ...\ ]\*(C'\fR are separate parameters, and must be
surrounded by spaces.  \f(CW\*(C`\-\-\*(C'\fR separates nbdinfo parameters from
subprocess parameters.
.SS "Alternative tools"
.IX Subsection "Alternative tools"
You could use \f(CW\*(C`qemu\-img\ info\*(C'\fR (see \fBqemu\-img\fR\|(1)) to query a
single export from an NBD server.  \f(CW\*(C`qemu\-nbd\ \-L\*(C'\fR (see
\&\fBqemu\-nbd\fR\|(8)) can list NBD exports.  \fBnbdsh\fR\|(1) or the \fBlibnbd\fR\|(3)
API can be used for more complex queries.
.SH OPTIONS
.IX Header "OPTIONS"
.IP \fB\-\-help\fR 4
.IX Item "--help"
Display brief command line help and exit.
.IP "\fB\-\-can block-status-payload\fR" 4
.IX Item "--can block-status-payload"
.PD 0
.IP "\fB\-\-can cache\fR" 4
.IX Item "--can cache"
.IP "\fB\-\-can connect\fR" 4
.IX Item "--can connect"
.IP "\fB\-\-can df\fR" 4
.IX Item "--can df"
.IP "\fB\-\-can fast-zero\fR" 4
.IX Item "--can fast-zero"
.IP "\fB\-\-can flush\fR" 4
.IX Item "--can flush"
.IP "\fB\-\-can fua\fR" 4
.IX Item "--can fua"
.IP "\fB\-\-can multi-conn\fR" 4
.IX Item "--can multi-conn"
.IP "\fB\-\-can read\fR" 4
.IX Item "--can read"
.IP "\fB\-\-can trim\fR" 4
.IX Item "--can trim"
.IP "\fB\-\-can write\fR" 4
.IX Item "--can write"
.IP "\fB\-\-can zero\fR" 4
.IX Item "--can zero"
.PD
Test properties of the NBD server export.  The command does not print
anything.  Instead it exits with success (exit\ code\ 0) if true, or
failure (exit\ code\ 2) if false.  (Other exit codes indicate an
error querying the flag).
.Sp
For further information see the NBD
protocol
and the following libnbd functions:
\&\fBnbd_can_block_status_payload\fR\|(3), \fBnbd_can_cache\fR\|(3),
\&\fBnbd_can_df\fR\|(3), \fBnbd_can_fast_zero\fR\|(3), \fBnbd_can_flush\fR\|(3),
\&\fBnbd_can_fua\fR\|(3), \fBnbd_can_multi_conn\fR\|(3), \fBnbd_can_trim\fR\|(3),
\&\fBnbd_can_zero\fR\|(3), \fBnbd_is_read_only\fR\|(3).
.IP "\fB\-\-cannot\fR flag" 4
.IX Item "--cannot flag"
Test the negation of flag.
.IP \fB\-\-color\fR 4
.IX Item "--color"
.PD 0
.IP \fB\-\-colour\fR 4
.IX Item "--colour"
.IP \fB\-\-no\-color\fR 4
.IX Item "--no-color"
.IP \fB\-\-no\-colour\fR 4
.IX Item "--no-colour"
.PD
Enable or disable ANSI colours in output.  By default we use colours
if the output seems to be a terminal, and disable them if not.
.IP \fB\-\-content\fR 4
.IX Item "--content"
.PD 0
.IP \fB\-\-no\-content\fR 4
.IX Item "--no-content"
.PD
Mostly the information displayed comes from the metadata sent by the
NBD server during the handshake.  However nbdinfo also downloads a
small amount of data from the beginning of the export to try to probe
the content with \fBfile\fR\|(1).
.Sp
When \fInot\fR using \fI\-\-list\fR, the default is \fI\-\-content\fR, ie.  probing
the content.  To prevent content probing, use \fI\-\-no\-content\fR.
.Sp
When using \fI\-\-list\fR, the default is \fI\-\-no\-content\fR (since
downloading from each export is expensive).  To enable content probing
use \fI\-\-list \-\-content\fR.
.IP "\fB\-\-has extended-headers\fR" 4
.IX Item "--has extended-headers"
.PD 0
.IP "\fB\-\-has structured-reply\fR" 4
.IX Item "--has structured-reply"
.PD
Test properties of the NBD server connection.  The command does not
print anything.  Instead it exits with success (exit\ code\ 0) if
true, or failure (exit\ code\ 2) if false.  (Other exit codes
indicate an error querying the flag).
.Sp
For further information see the NBD
protocol
and the following libnbd functions:
\&\fBnbd_get_extended_headers_negotiated\fR\|(3),
\&\fBnbd_get_structured_replies_negotiated\fR\|(3).
.IP "\fB\-\-hasnt\fR flag" 4
.IX Item "--hasnt flag"
Test the negation of flag.
.IP "\fB\-\-is read-only\fR" 4
.IX Item "--is read-only"
.PD 0
.IP "\fB\-\-is rotational\fR" 4
.IX Item "--is rotational"
.IP "\fB\-\-is tls\fR" 4
.IX Item "--is tls"
.PD
Test if the NBD server export is read-only and rotational, or whether
the connection itself is using TLS.  The command does not print
anything.  Instead it exits with success (exit\ code\ 0) if true, or
failure (exit\ code\ 2) if false.  (Other exit codes indicate an
error querying the flag).
.Sp
For further information see the NBD
protocol
and the following libnbd functions: \fBnbd_is_read_only\fR\|(3),
\&\fBnbd_is_rotational\fR\|(3), \fBnbd_get_tls_negotiated\fR\|(3).
.IP "\fB\-\-isnt\fR flag" 4
.IX Item "--isnt flag"
Test the negation of flag.
.IP \fB\-\-json\fR 4
.IX Item "--json"
The output is displayed in JSON format.
.IP \fB\-L\fR 4
.IX Item "-L"
.PD 0
.IP \fB\-\-list\fR 4
.IX Item "--list"
.PD
List all the exports on an NBD server.  The export name in the NBD URI
is ignored.
.IP \fB\-\-map\fR 4
.IX Item "--map"
.PD 0
.IP \fB\-\-map=\fRMAP 4
.IX Item "--map=MAP"
.PD
Display the map (usually whether parts of the disk are allocated or
sparse) of the given export.  This displays the \f(CW"base:allocation"\fR
map by default, you can choose a different map with the optional
parameter.
.Sp
See the "Map" section above.
.IP "\fB\-\-map\fR \fB\-\-totals\fR" 4
.IX Item "--map --totals"
.PD 0
.IP "\fB\-\-map=\fRMAP \fB\-\-totals\fR" 4
.IX Item "--map=MAP --totals"
.PD
The same as \fI\-\-map\fR, but displays a summary of the total size of each
type of allocation.
.Sp
See the "Map totals" section above.
.IP \fB\-\-size\fR 4
.IX Item "--size"
Display only the size in bytes of the export.
.IP \fB\-\-uri\fR 4
.IX Item "--uri"
Display only the canonical URI.  If combined with \fI\-\-json\fR then the
output is a JSON-quoted string.
.IP \fB\-V\fR 4
.IX Item "-V"
.PD 0
.IP \fB\-\-version\fR 4
.IX Item "--version"
.PD
Display the package name and version and exit.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBlibnbd\fR\|(3),
\&\fBnbdcopy\fR\|(1),
\&\fBnbddump\fR\|(1),
\&\fBnbdfuse\fR\|(1),
\&\fBnbdsh\fR\|(1),
\&\fBnbdublk\fR\|(1),
\&\fBfile\fR\|(1),
\&\fBjq\fR\|(1),
\&\fBqemu\-img\fR\|(1),
\&\fBqemu\-nbd\fR\|(8).
.SH AUTHORS
.IX Header "AUTHORS"
Richard W.M. Jones
.PP
Eric Blake
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright Red Hat
.SH LICENSE
.IX Header "LICENSE"
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.
.PP
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.
.PP
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110\-1301 USA