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qemu-img is a QEMU disk image utility

The program is used to create, snapshot, clone, and shutdown disk image.

Introduction

qemu-img creates, maintains, appends, and converts a block storage unit for use with most any virtual machines.

A complete list of storage format (-f <format-type>) option are:

Format Option (-f)	Format Type	Description
blkdebug	pseudo-format	Used to inject rule-based errors into a block storage in exercising various error code path within qcow2 block driver. Primarily used with QEMU unit test cases.
blklogwrites	pseudo	Writes log of write operations on a monitored backend (host-side) block storage file.
blkverify	pseudo	Performs correctness of block integrity by monitoring for data corruption on the guest-side (inside); useful with blklogwrites and blkdebug unit tests.
bochs	read-only	Bochs image format
cloop	read-only	Linux compressed loop image used commonly with compressed CD-ROMs image format (such as Knoppix CD-ROM).
compress
copy-before-write
copy-on-read
dmg	read-only	Apple Disk Image
file
ftp
ftps
gluster	network	Accesses the user space distributed file system
host_cdrom
host_device
http
https
iscsi	network	Accesses the remote SCSI device.
iser
luks	pseudo	luks is used to open the LUKS v1 backing storage for copy-on-write operations
nbd	network	Access remote image device that were exported using Network Block Device protocol
nfs
null-aio
null-co
nvme	block	Access the NVM Express (NVMe) storage controllers directly by userspace driver in QEMU. Useful for fastest operation.
parallels	read-only	Parallels virtual machine image format
preallocate	filter	A shim-module for pre-allocation some additional space when writing beyond file's EOF. Good for slow-allocation system.
qcow	block	Older version of qcow2.
qcow2	block	The most common choice of file format in QEMU virtual machines.
qed	block	Original QEMU block image format. Obsoleted by qcow2 and qcow format.
quorum
raw	block	The simplest way for guest OS to directly write as-is to the host OS block storage.
rbd
replication	pseudo	Used to open the backing storage device for copy-on-write operations
snapshot-access
ssh	network	Accesses the disk images on a remote SSH server
throttle
vdi	block	VirtualBox v1.1 compatible image format
vhdx	block	Hyper-V compatible image format
vmdk	block	VMware 3 and 4 compatible image format
vpc	block	VirtualPC compatible image format. A headerless block disk image used for backing stores. Often used with obsoleted qed image format.
vvfat	block	Virtual VFAT file system that is commonly found in Microsoft Windows and MS-DOS and clones. Can handle 12-bit, 16-bit, and 32-bit VFAT.

Installation

See QEMU Installation for installation of qemu-img.

Configuration

Environment variables

A list of all environment variables that are read and checked by the qemu-img command:

• SDL_VIDEODRIVER - Sets to either x11 or sdl if cannot be automatically determined.
• LISTEN_FDNAMES - Pass the socket name descriptor(s) of the QEMU Disk Block Device to the systemd-socketd socket activation daemon.
• LISTEN_FDS - Pass the file descriptor(s) (fds) of the QEMU Disk Block Device to the systemd-socketd socket activation daemon.
• LISTEN_PID - Pass the process ID (PID) of the QEMU Disk Block Device to the systemd-socketd socket activation daemon.
• QEMU_MODULE_DIR - Base directory path spec to the QEMU modules.
• QEMU_AUDIO_DRV
• QEMU_PATH
• G_MESSAGES_DEBUG - Error reporting
• QEMU_STRACE - Enable <cmd>strace</cmd> (only on BSD)
• XDG_RUNTIME_DIR - pass audio settings to the PulseAudio daemon/driver.

Files

Files that are read by the host-side OS qemu-img command:

• /dev/cdrom
• /dev/fdset
• /dev/null
• /dev/vfio/<device-name>
• /proc/<PID>/cmdline
• /proc/self/exe
• /proc/self/fd
• /proc/sys/vm/overcommit_memory
• /sys/bus/pci/devices/%s/iommu_group

Files that are written by the host-side OS qemu-img command:

• /var/run/qemu/qemu-socket-<TMPID>
• /var/tmp/

User permissions

To use qemu-img as a non-root user, ensure each user has been added to the qemu group:

root #gpasswd -a <user> qemu

See qemu-img configuration for more setup on enabling user to use the qemu-img command.

Usage

The qemu-img can be checked by running:

root #qemu-img info /dev/sda

image: /dev/sda
file format: raw
virtual size: 187 GiB (201188179968 bytes)
disk size: 0 B
}}


=== Invocation ===

{{Invocation|qemu-img --help|collapse-output=true|output=<pre>
qemu-img version 7.2.9 (Debian 1:7.2+dfsg-7+deb12u5)
Copyright (c) 2003-2022 Fabrice Bellard and the QEMU Project developers
usage: qemu-img [standard options] command [command options]
QEMU disk image utility

    '-h', '--help'       display this help and exit
    '-V', '--version'    output version information and exit
    '-T', '--trace'      [[enable=]<pattern>][,events=<file>][,file=<file>]
                         specify tracing options

Command syntax:
  amend [--object objectdef] [--image-opts] [-p] [-q] [-f fmt] [-t cache] [--force] -o options filename
  bench [-c count] [-d depth] [-f fmt] [--flush-interval=flush_interval] [-i aio] [-n] [--no-drain] [-o offset] [--pattern=pattern] [-q] [-s buffer_size] [-S step_size] [-t cache] [-w] [-U] filename
  bitmap (--merge SOURCE | --add | --remove | --clear | --enable | --disable)... [-b source_file [-F source_fmt]] [-g granularity] [--object objectdef] [--image-opts | -f fmt] filename bitmap
  check [--object objectdef] [--image-opts] [-q] [-f fmt] [--output=ofmt] [-r [leaks | all]] [-T src_cache] [-U] filename
  commit [--object objectdef] [--image-opts] [-q] [-f fmt] [-t cache] [-b base] [-r rate_limit] [-d] [-p] filename
  compare [--object objectdef] [--image-opts] [-f fmt] [-F fmt] [-T src_cache] [-p] [-q] [-s] [-U] filename1 filename2
  convert [--object objectdef] [--image-opts] [--target-image-opts] [--target-is-zero] [--bitmaps] [-U] [-C] [-c] [-p] [-q] [-n] [-f fmt] [-t cache] [-T src_cache] [-O output_fmt] [-B backing_file [-F backing_fmt]] [-o options] [-l snapshot_param] [-S sparse_size] [-r rate_limit] [-m num_coroutines] [-W] [--salvage] filename [filename2 [...]] output_filename
  create [--object objectdef] [-q] [-f fmt] [-b backing_file [-F backing_fmt]] [-u] [-o options] filename [size]
  dd [--image-opts] [-U] [-f fmt] [-O output_fmt] [bs=block_size] [count=blocks] [skip=blocks] if=input of=output
  info [--object objectdef] [--image-opts] [-f fmt] [--output=ofmt] [--backing-chain] [-U] filename
  map [--object objectdef] [--image-opts] [-f fmt] [--start-offset=offset] [--max-length=len] [--output=ofmt] [-U] filename
  measure [--output=ofmt] [-O output_fmt] [-o options] [--size N | [--object objectdef] [--image-opts] [-f fmt] [-l snapshot_param] filename]
  snapshot [--object objectdef] [--image-opts] [-U] [-q] [-l | -a snapshot | -c snapshot | -d snapshot] filename
  rebase [--object objectdef] [--image-opts] [-U] [-q] [-f fmt] [-t cache] [-T src_cache] [-p] [-u] -b backing_file [-F backing_fmt] filename
  resize [--object objectdef] [--image-opts] [-f fmt] [--preallocation=prealloc] [-q] [--shrink] filename [+ | -]size

Command parameters:
  'filename' is a disk image filename
  'objectdef' is a QEMU user creatable object definition. See the qemu(1)
    manual page for a description of the object properties. The most common
    object type is a 'secret', which is used to supply passwords and/or
    encryption keys.
  'fmt' is the disk image format. It is guessed automatically in most cases
  'cache' is the cache mode used to write the output disk image, the valid
    options are: 'none', 'writeback' (default, except for convert), 'writethrough',
    'directsync' and 'unsafe' (default for convert)
  'src_cache' is the cache mode used to read input disk images, the valid
    options are the same as for the 'cache' option
  'size' is the disk image size in bytes. Optional suffixes
    'k' or 'K' (kilobyte, 1024), 'M' (megabyte, 1024k), 'G' (gigabyte, 1024M),
    'T' (terabyte, 1024G), 'P' (petabyte, 1024T) and 'E' (exabyte, 1024P)  are
    supported. 'b' is ignored.
  'output_filename' is the destination disk image filename
  'output_fmt' is the destination format
  'options' is a comma separated list of format specific options in a
    name=value format. Use -o help for an overview of the options supported by
    the used format
  'snapshot_param' is param used for internal snapshot, format
    is 'snapshot.id=[ID],snapshot.name=[NAME]', or
    '[ID_OR_NAME]'
  '-c' indicates that target image must be compressed (qcow format only)
  '-u' allows unsafe backing chains. For rebasing, it is assumed that old and
       new backing file match exactly. The image doesn't need a working
       backing file before rebasing in this case (useful for renaming the
       backing file). For image creation, allow creating without attempting
       to open the backing file.
  '-h' with or without a command shows this help and lists the supported formats
  '-p' show progress of command (only certain commands)
  '-q' use Quiet mode - do not print any output (except errors)
  '-S' indicates the consecutive number of bytes (defaults to 4k) that must
       contain only zeros for qemu-img to create a sparse image during
       conversion. If the number of bytes is 0, the source will not be scanned for
       unallocated or zero sectors, and the destination image will always be
       fully allocated
  '--output' takes the format in which the output must be done (human or json)
  '-n' skips the target volume creation (useful if the volume is created
       prior to running qemu-img)

Parameters to bitmap subcommand:
  'bitmap' is the name of the bitmap to manipulate, through one or more
       actions from '--add', '--remove', '--clear', '--enable', '--disable',
       or '--merge source'
  '-g granularity' sets the granularity for '--add' actions
  '-b source' and '-F src_fmt' tell '--merge' actions to find the source
       bitmaps from an alternative file

Parameters to check subcommand:
  '-r' tries to repair any inconsistencies that are found during the check.
       '-r leaks' repairs only cluster leaks, whereas '-r all' fixes all
       kinds of errors, with a higher risk of choosing the wrong fix or
       hiding corruption that has already occurred.

Parameters to convert subcommand:
  '--bitmaps' copies all top-level persistent bitmaps to destination
  '-m' specifies how many coroutines work in parallel during the convert
       process (defaults to 8)
  '-W' allow to write to the target out of order rather than sequential

Parameters to snapshot subcommand:
  'snapshot' is the name of the snapshot to create, apply or delete
  '-a' applies a snapshot (revert disk to saved state)
  '-c' creates a snapshot
  '-d' deletes a snapshot
  '-l' lists all snapshots in the given image

Parameters to compare subcommand:
  '-f' first image format
  '-F' second image format
  '-s' run in Strict mode - fail on different image size or sector allocation

Parameters to dd subcommand:
  'bs=BYTES' read and write up to BYTES bytes at a time (default: 512)
  'count=N' copy only N input blocks
  'if=FILE' read from FILE
  'of=FILE' write to FILE
  'skip=N' skip N bs-sized blocks at the start of input

Supported formats: blkdebug blklogwrites blkverify bochs cloop compress copy-before-write copy-on-read dmg file ftp ftps gluster host_cdrom host_device http https iscsi iser luks nbd nfs null-aio null-co nvme parallels preallocate qcow qcow2 qed quorum raw rbd replication snapshot-access ssh throttle vdi vhdx vmdk vpc vvfat

See <https://qemu.org/contribute/report-a-bug> for how to report bugs.
More information on the QEMU project at <https://qemu.org>.
wolfe@mensa:~/work/qemu/qemu-utils/qemu-7.2+dfsg$ qemu-img --help
qemu-img version 7.2.9 (Debian 1:7.2+dfsg-7+deb12u5)
Copyright (c) 2003-2022 Fabrice Bellard and the QEMU Project developers
usage: qemu-img [standard options] command [command options]
QEMU disk image utility

    '-h', '--help'       display this help and exit
    '-V', '--version'    output version information and exit
    '-T', '--trace'      [[enable=]<pattern>][,events=<file>][,file=<file>]
                         specify tracing options

Command syntax:
  amend [--object objectdef] [--image-opts] [-p] [-q] [-f fmt] [-t cache] [--force] -o options filename
  bench [-c count] [-d depth] [-f fmt] [--flush-interval=flush_interval] [-i aio] [-n] [--no-drain] [-o offset] [--pattern=pattern] [-q] [-s buffer_size] [-S step_size] [-t cache] [-w] [-U] filename
  bitmap (--merge SOURCE | --add | --remove | --clear | --enable | --disable)... [-b source_file [-F source_fmt]] [-g granularity] [--object objectdef] [--image-opts | -f fmt] filename bitmap
  check [--object objectdef] [--image-opts] [-q] [-f fmt] [--output=ofmt] [-r [leaks | all]] [-T src_cache] [-U] filename
  commit [--object objectdef] [--image-opts] [-q] [-f fmt] [-t cache] [-b base] [-r rate_limit] [-d] [-p] filename
  compare [--object objectdef] [--image-opts] [-f fmt] [-F fmt] [-T src_cache] [-p] [-q] [-s] [-U] filename1 filename2
  convert [--object objectdef] [--image-opts] [--target-image-opts] [--target-is-zero] [--bitmaps] [-U] [-C] [-c] [-p] [-q] [-n] [-f fmt] [-t cache] [-T src_cache] [-O output_fmt] [-B backing_file [-F backing_fmt]] [-o options] [-l snapshot_param] [-S sparse_size] [-r rate_limit] [-m num_coroutines] [-W] [--salvage] filename [filename2 [...]] output_filename
  create [--object objectdef] [-q] [-f fmt] [-b backing_file [-F backing_fmt]] [-u] [-o options] filename [size]
  dd [--image-opts] [-U] [-f fmt] [-O output_fmt] [bs=block_size] [count=blocks] [skip=blocks] if=input of=output
  info [--object objectdef] [--image-opts] [-f fmt] [--output=ofmt] [--backing-chain] [-U] filename
  map [--object objectdef] [--image-opts] [-f fmt] [--start-offset=offset] [--max-length=len] [--output=ofmt] [-U] filename
  measure [--output=ofmt] [-O output_fmt] [-o options] [--size N | [--object objectdef] [--image-opts] [-f fmt] [-l snapshot_param] filename]
  snapshot [--object objectdef] [--image-opts] [-U] [-q] [-l | -a snapshot | -c snapshot | -d snapshot] filename
  rebase [--object objectdef] [--image-opts] [-U] [-q] [-f fmt] [-t cache] [-T src_cache] [-p] [-u] -b backing_file [-F backing_fmt] filename
  resize [--object objectdef] [--image-opts] [-f fmt] [--preallocation=prealloc] [-q] [--shrink] filename [+ | -]size

Command parameters:
  'filename' is a disk image filename
  'objectdef' is a QEMU user creatable object definition. See the qemu(1)
    manual page for a description of the object properties. The most common
    object type is a 'secret', which is used to supply passwords and/or
    encryption keys.
  'fmt' is the disk image format. It is guessed automatically in most cases
  'cache' is the cache mode used to write the output disk image, the valid
    options are: 'none', 'writeback' (default, except for convert), 'writethrough',
    'directsync' and 'unsafe' (default for convert)
  'src_cache' is the cache mode used to read input disk images, the valid
    options are the same as for the 'cache' option
  'size' is the disk image size in bytes. Optional suffixes
    'k' or 'K' (kilobyte, 1024), 'M' (megabyte, 1024k), 'G' (gigabyte, 1024M),
    'T' (terabyte, 1024G), 'P' (petabyte, 1024T) and 'E' (exabyte, 1024P)  are
    supported. 'b' is ignored.
  'output_filename' is the destination disk image filename
  'output_fmt' is the destination format
  'options' is a comma separated list of format specific options in a
    name=value format. Use -o help for an overview of the options supported by
    the used format
  'snapshot_param' is param used for internal snapshot, format
    is 'snapshot.id=[ID],snapshot.name=[NAME]', or
    '[ID_OR_NAME]'
  '-c' indicates that target image must be compressed (qcow format only)
  '-u' allows unsafe backing chains. For rebasing, it is assumed that old and
       new backing file match exactly. The image doesn't need a working
       backing file before rebasing in this case (useful for renaming the
       backing file). For image creation, allow creating without attempting
       to open the backing file.
  '-h' with or without a command shows this help and lists the supported formats
  '-p' show progress of command (only certain commands)
  '-q' use Quiet mode - do not print any output (except errors)
  '-S' indicates the consecutive number of bytes (defaults to 4k) that must
       contain only zeros for qemu-img to create a sparse image during
       conversion. If the number of bytes is 0, the source will not be scanned for
       unallocated or zero sectors, and the destination image will always be
       fully allocated
  '--output' takes the format in which the output must be done (human or json)
  '-n' skips the target volume creation (useful if the volume is created
       prior to running qemu-img)

Parameters to bitmap subcommand:
  'bitmap' is the name of the bitmap to manipulate, through one or more
       actions from '--add', '--remove', '--clear', '--enable', '--disable',
       or '--merge source'
  '-g granularity' sets the granularity for '--add' actions
  '-b source' and '-F src_fmt' tell '--merge' actions to find the source
       bitmaps from an alternative file

Parameters to check subcommand:
  '-r' tries to repair any inconsistencies that are found during the check.
       '-r leaks' repairs only cluster leaks, whereas '-r all' fixes all
       kinds of errors, with a higher risk of choosing the wrong fix or
       hiding corruption that has already occurred.

Parameters to convert subcommand:
  '--bitmaps' copies all top-level persistent bitmaps to destination
  '-m' specifies how many coroutines work in parallel during the convert
       process (defaults to 8)
  '-W' allow to write to the target out of order rather than sequential

Parameters to snapshot subcommand:
  'snapshot' is the name of the snapshot to create, apply or delete
  '-a' applies a snapshot (revert disk to saved state)
  '-c' creates a snapshot
  '-d' deletes a snapshot
  '-l' lists all snapshots in the given image

Parameters to compare subcommand:
  '-f' first image format
  '-F' second image format
  '-s' run in Strict mode - fail on different image size or sector allocation

Parameters to dd subcommand:
  'bs=BYTES' read and write up to BYTES bytes at a time (default: 512)
  'count=N' copy only N input blocks
  'if=FILE' read from FILE
  'of=FILE' write to FILE
  'skip=N' skip N bs-sized blocks at the start of input

Supported formats: blkdebug blklogwrites blkverify bochs cloop compress copy-before-write copy-on-read dmg file ftp ftps gluster host_cdrom host_device http https iscsi iser luks nbd nfs null-aio null-co nvme parallels preallocate qcow qcow2 qed quorum raw rbd replication snapshot-access ssh throttle vdi vhdx vmdk vpc vvfat

See <https://qemu.org/contribute/report-a-bug> for how to report bugs.
More information on the QEMU project at <https://qemu.org>.

Removal

Removal of qemu-img package (toolkit, library, and utilities) can be done by executing:

root #emerge --ask --depclean --verbose app-emulation/qemu-img

See also

• QEMU — a generic, open source hardware emulator and virtualization suite.
• QEMU/QEMU front-ends