F: hw/block/
F: include/block/
F: qemu-img*
+F: docs/interop/qemu-img.rst
F: qemu-io*
F: tests/qemu-iotests/
F: util/qemu-progress.c
endif
ifdef BUILD_DOCS
-DOCS=qemu-doc.html qemu-doc.txt qemu.1 qemu-img.1
+DOCS=qemu-doc.html qemu-doc.txt qemu.1
+DOCS+=$(MANUAL_BUILDDIR)/interop/qemu-img.1
DOCS+=$(MANUAL_BUILDDIR)/interop/qemu-nbd.8
DOCS+=$(MANUAL_BUILDDIR)/interop/qemu-ga.8
DOCS+=$(MANUAL_BUILDDIR)/system/qemu-block-drivers.7
endef
distclean: clean
- rm -f config-host.mak config-host.h* config-host.ld $(DOCS) qemu-options.texi qemu-img-cmds.texi qemu-monitor.texi qemu-monitor-info.texi
+ rm -f config-host.mak config-host.h* config-host.ld $(DOCS) qemu-options.texi qemu-monitor.texi qemu-monitor-info.texi
rm -f tests/tcg/config-*.mak
rm -f config-all-devices.mak config-all-disas.mak config.status
rm -f $(SUBDIR_DEVICES_MAK)
$(INSTALL_DATA) $(MANUAL_BUILDDIR)/system/qemu-block-drivers.7 "$(DESTDIR)$(mandir)/man7"
$(INSTALL_DATA) docs/qemu-cpu-models.7 "$(DESTDIR)$(mandir)/man7"
ifeq ($(CONFIG_TOOLS),y)
- $(INSTALL_DATA) qemu-img.1 "$(DESTDIR)$(mandir)/man1"
+ $(INSTALL_DATA) $(MANUAL_BUILDDIR)/interop/qemu-img.1 "$(DESTDIR)$(mandir)/man1"
$(INSTALL_DIR) "$(DESTDIR)$(mandir)/man8"
$(INSTALL_DATA) $(MANUAL_BUILDDIR)/interop/qemu-nbd.8 "$(DESTDIR)$(mandir)/man8"
endif
$(MANUAL_BUILDDIR)/devel/index.html: $(call manual-deps,devel)
$(call build-manual,devel,html)
-$(MANUAL_BUILDDIR)/interop/index.html: $(call manual-deps,interop)
+$(MANUAL_BUILDDIR)/interop/index.html: $(call manual-deps,interop) $(SRC_PATH)/qemu-img-cmds.hx
$(call build-manual,interop,html)
$(MANUAL_BUILDDIR)/specs/index.html: $(call manual-deps,specs)
$(MANUAL_BUILDDIR)/system/index.html: $(call manual-deps,system)
$(call build-manual,system,html)
-$(call define-manpage-rule,interop,qemu-ga.8 qemu-nbd.8)
+$(call define-manpage-rule,interop,qemu-ga.8 qemu-img.1 qemu-nbd.8,$(SRC_PATH/qemu-img-cmds.hx))
$(call define-manpage-rule,system,qemu-block-drivers.7)
qemu-monitor-info.texi: $(SRC_PATH)/hmp-commands-info.hx $(SRC_PATH)/scripts/hxtool
$(call quiet-command,sh $(SRC_PATH)/scripts/hxtool -t < $< > $@,"GEN","$@")
-qemu-img-cmds.texi: $(SRC_PATH)/qemu-img-cmds.hx $(SRC_PATH)/scripts/hxtool
- $(call quiet-command,sh $(SRC_PATH)/scripts/hxtool -t < $< > $@,"GEN","$@")
-
docs/interop/qemu-qmp-qapi.texi: qapi/qapi-doc.texi
@cp -p $< $@
qemu.1: qemu-doc.texi qemu-options.texi qemu-monitor.texi qemu-monitor-info.texi
qemu.1: qemu-option-trace.texi
-qemu-img.1: qemu-img.texi qemu-option-trace.texi qemu-img-cmds.texi
fsdev/virtfs-proxy-helper.1: fsdev/virtfs-proxy-helper.texi
docs/qemu-cpu-models.7: docs/qemu-cpu-models.texi
scripts/qemu-trace-stap.1: scripts/qemu-trace-stap.texi
txt: qemu-doc.txt docs/interop/qemu-qmp-ref.txt docs/interop/qemu-ga-ref.txt
qemu-doc.html qemu-doc.info qemu-doc.pdf qemu-doc.txt: \
- qemu-img.texi qemu-options.texi \
+ qemu-options.texi \
qemu-tech.texi qemu-option-trace.texi \
- qemu-deprecated.texi qemu-monitor.texi qemu-img-cmds.texi \
+ qemu-deprecated.texi qemu-monitor.texi \
qemu-monitor-info.texi \
docs/qemu-cpu-models.texi docs/security.texi
man_pages = [
('qemu-ga', 'qemu-ga', u'QEMU Guest Agent',
['Michael Roth <mdroth@linux.vnet.ibm.com>'], 8),
+ ('qemu-img', 'qemu-img', u'QEMU disk image utility',
+ ['Fabrice Bellard'], 1),
('qemu-nbd', 'qemu-nbd', u'QEMU Disk Network Block Device Server',
['Anthony Liguori <anthony@codemonkey.ws>'], 8)
]
live-block-operations
pr-helper
qemu-ga
+ qemu-img
qemu-nbd
vhost-user
vhost-user-gpu
--- /dev/null
+QEMU disk image utility
+=======================
+
+Synopsis
+--------
+
+**qemu-img** [*standard options*] *command* [*command options*]
+
+Description
+-----------
+
+qemu-img allows you to create, convert and modify images offline. It can handle
+all image formats supported by QEMU.
+
+**Warning:** Never use qemu-img to modify images in use by a running virtual
+machine or any other process; this may destroy the image. Also, be aware that
+querying an image that is being modified by another process may encounter
+inconsistent state.
+
+Options
+-------
+
+.. program:: qemu-img
+
+Standard options:
+
+.. option:: -h, --help
+
+ Display this help and exit
+
+.. option:: -V, --version
+
+ Display version information and exit
+
+.. option:: -T, --trace [[enable=]PATTERN][,events=FILE][,file=FILE]
+
+ .. include:: qemu-option-trace.rst.inc
+
+The following commands are supported:
+
+.. hxtool-doc:: qemu-img-cmds.hx
+
+Command parameters:
+
+*FILENAME* is a disk image filename.
+
+*FMT* is the disk image format. It is guessed automatically in most
+cases. See below for a description of the supported disk formats.
+
+*SIZE* is the disk image size in bytes. Optional suffixes ``k`` or
+``K`` (kilobyte, 1024) ``M`` (megabyte, 1024k) and ``G`` (gigabyte,
+1024M) and T (terabyte, 1024G) 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 ?`` for an overview of the options supported
+by the used format or see the format descriptions below for details.
+
+*SNAPSHOT_PARAM* is param used for internal snapshot, format is
+'snapshot.id=[ID],snapshot.name=[NAME]' or '[ID_OR_NAME]'.
+
+..
+ Note the use of a new 'program'; otherwise Sphinx complains about
+ the -h option appearing both in the above option list and this one.
+
+.. program:: qemu-img-common-opts
+
+.. option:: --object OBJECTDEF
+
+ is a QEMU user creatable object definition. See the :manpage:`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.
+
+.. option:: --image-opts
+
+ Indicates that the source *FILENAME* parameter is to be interpreted as a
+ full option string, not a plain filename. This parameter is mutually
+ exclusive with the *-f* parameter.
+
+.. option:: --target-image-opts
+
+ Indicates that the OUTPUT_FILENAME parameter(s) are to be interpreted as
+ a full option string, not a plain filename. This parameter is mutually
+ exclusive with the *-O* parameters. It is currently required to also use
+ the *-n* parameter to skip image creation. This restriction may be relaxed
+ in a future release.
+
+.. option:: --force-share (-U)
+
+ If specified, ``qemu-img`` will open the image in shared mode, allowing
+ other QEMU processes to open it in write mode. For example, this can be used to
+ get the image information (with 'info' subcommand) when the image is used by a
+ running guest. Note that this could produce inconsistent results because of
+ concurrent metadata changes, etc. This option is only allowed when opening
+ images in read-only mode.
+
+.. option:: --backing-chain
+
+ Will enumerate information about backing files in a disk image chain. Refer
+ below for further description.
+
+.. option:: -c
+
+ Indicates that target image must be compressed (qcow format only).
+
+.. option:: -h
+
+ With or without a command, shows help and lists the supported formats.
+
+.. option:: -p
+
+ Display progress bar (compare, convert and rebase commands only).
+ If the *-p* option is not used for a command that supports it, the
+ progress is reported when the process receives a ``SIGUSR1`` or
+ ``SIGINFO`` signal.
+
+.. option:: -q
+
+ Quiet mode - do not print any output (except errors). There's no progress bar
+ in case both *-q* and *-p* options are used.
+
+.. option:: -S SIZE
+
+ Indicates the consecutive number of bytes that must contain only zeros
+ for qemu-img to create a sparse image during conversion. This value is rounded
+ down to the nearest 512 bytes. You may use the common size suffixes like
+ ``k`` for kilobytes.
+
+.. option:: -t CACHE
+
+ Specifies the cache mode that should be used with the (destination) file. See
+ the documentation of the emulator's ``-drive cache=...`` option for allowed
+ values.
+
+.. option:: -T SRC_CACHE
+
+ Specifies the cache mode that should be used with the source file(s). See
+ the documentation of the emulator's ``-drive cache=...`` option for allowed
+ values.
+
+Parameters to snapshot subcommand:
+
+.. program:: qemu-img-snapshot
+
+.. option:: snapshot
+
+ Is the name of the snapshot to create, apply or delete
+
+.. option:: -a
+
+ Applies a snapshot (revert disk to saved state)
+
+.. option:: -c
+
+ Creates a snapshot
+
+.. option:: -d
+
+ Deletes a snapshot
+
+.. option:: -l
+
+ Lists all snapshots in the given image
+
+Parameters to compare subcommand:
+
+.. program:: qemu-img-compare
+
+.. option:: -f
+
+ First image format
+
+.. option:: -F
+
+ Second image format
+
+.. option:: -s
+
+ Strict mode - fail on different image size or sector allocation
+
+Parameters to convert subcommand:
+
+.. program:: qemu-img-convert
+
+.. option:: -n
+
+ Skip the creation of the target volume
+
+.. option:: -m
+
+ Number of parallel coroutines for the convert process
+
+.. option:: -W
+
+ Allow out-of-order writes to the destination. This option improves performance,
+ but is only recommended for preallocated devices like host devices or other
+ raw block devices.
+
+.. option:: -C
+
+ Try to use copy offloading to move data from source image to target. This may
+ improve performance if the data is remote, such as with NFS or iSCSI backends,
+ but will not automatically sparsify zero sectors, and may result in a fully
+ allocated target image depending on the host support for getting allocation
+ information.
+
+.. option:: --salvage
+
+ Try to ignore I/O errors when reading. Unless in quiet mode (``-q``), errors
+ will still be printed. Areas that cannot be read from the source will be
+ treated as containing only zeroes.
+
+Parameters to dd subcommand:
+
+.. program:: qemu-img-dd
+
+.. option:: bs=BLOCK_SIZE
+
+ Defines the block size
+
+.. option:: count=BLOCKS
+
+ Sets the number of input blocks to copy
+
+.. option:: if=INPUT
+
+ Sets the input file
+
+.. option:: of=OUTPUT
+
+ Sets the output file
+
+.. option:: skip=BLOCKS
+
+ Sets the number of input blocks to skip
+
+Command description:
+
+.. program:: qemu-img-commands
+
+.. option:: amend [--object OBJECTDEF] [--image-opts] [-p] [-q] [-f FMT] [-t CACHE] -o OPTIONS FILENAME
+
+ Amends the image format specific *OPTIONS* for the image file
+ *FILENAME*. Not all file formats support this operation.
+
+.. option:: bench [-c COUNT] [-d DEPTH] [-f FMT] [--flush-interval=FLUSH_INTERVAL] [-n] [-i AIO] [--no-drain] [-o OFFSET] [--pattern=PATTERN] [-q] [-s BUFFER_SIZE] [-S STEP_SIZE] [-t CACHE] [-w] [-U] FILENAME
+
+ Run a simple sequential I/O benchmark on the specified image. If ``-w`` is
+ specified, a write test is performed, otherwise a read test is performed.
+
+ A total number of *COUNT* I/O requests is performed, each *BUFFER_SIZE*
+ bytes in size, and with *DEPTH* requests in parallel. The first request
+ starts at the position given by *OFFSET*, each following request increases
+ the current position by *STEP_SIZE*. If *STEP_SIZE* is not given,
+ *BUFFER_SIZE* is used for its value.
+
+ If *FLUSH_INTERVAL* is specified for a write test, the request queue is
+ drained and a flush is issued before new writes are made whenever the number of
+ remaining requests is a multiple of *FLUSH_INTERVAL*. If additionally
+ ``--no-drain`` is specified, a flush is issued without draining the request
+ queue first.
+
+ If ``-n`` is specified, the native AIO backend is used if possible. On
+ Linux, this option only works if ``-t none`` or ``-t directsync`` is
+ specified as well.
+
+ if ``-i`` is specified, *AIO* option can be used to specify different
+ AIO backends: ``threads``, ``native`` or ``io_uring``.
+
+ For write tests, by default a buffer filled with zeros is written. This can be
+ overridden with a pattern byte specified by *PATTERN*.
+
+.. option:: check [--object OBJECTDEF] [--image-opts] [-q] [-f FMT] [--output=OFMT] [-r [leaks | all]] [-T SRC_CACHE] [-U] FILENAME
+
+ Perform a consistency check on the disk image *FILENAME*. The command can
+ output in the format *OFMT* which is either ``human`` or ``json``.
+ The JSON output is an object of QAPI type ``ImageCheck``.
+
+ If ``-r`` is specified, qemu-img tries to repair any inconsistencies 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.
+
+ Only the formats ``qcow2``, ``qed`` and ``vdi`` support
+ consistency checks.
+
+ In case the image does not have any inconsistencies, check exits with ``0``.
+ Other exit codes indicate the kind of inconsistency found or if another error
+ occurred. The following table summarizes all exit codes of the check subcommand:
+
+ 0
+ Check completed, the image is (now) consistent
+ 1
+ Check not completed because of internal errors
+ 2
+ Check completed, image is corrupted
+ 3
+ Check completed, image has leaked clusters, but is not corrupted
+ 63
+ Checks are not supported by the image format
+
+ If ``-r`` is specified, exit codes representing the image state refer to the
+ state after (the attempt at) repairing it. That is, a successful ``-r all``
+ will yield the exit code 0, independently of the image state before.
+
+.. option:: commit [--object OBJECTDEF] [--image-opts] [-q] [-f FMT] [-t CACHE] [-b BASE] [-d] [-p] FILENAME
+
+ Commit the changes recorded in *FILENAME* in its base image or backing file.
+ If the backing file is smaller than the snapshot, then the backing file will be
+ resized to be the same size as the snapshot. If the snapshot is smaller than
+ the backing file, the backing file will not be truncated. If you want the
+ backing file to match the size of the smaller snapshot, you can safely truncate
+ it yourself once the commit operation successfully completes.
+
+ The image *FILENAME* is emptied after the operation has succeeded. If you do
+ not need *FILENAME* afterwards and intend to drop it, you may skip emptying
+ *FILENAME* by specifying the ``-d`` flag.
+
+ If the backing chain of the given image file *FILENAME* has more than one
+ layer, the backing file into which the changes will be committed may be
+ specified as *BASE* (which has to be part of *FILENAME*'s backing
+ chain). If *BASE* is not specified, the immediate backing file of the top
+ image (which is *FILENAME*) will be used. Note that after a commit operation
+ all images between *BASE* and the top image will be invalid and may return
+ garbage data when read. For this reason, ``-b`` implies ``-d`` (so that
+ the top image stays valid).
+
+.. option:: compare [--object OBJECTDEF] [--image-opts] [-f FMT] [-F FMT] [-T SRC_CACHE] [-p] [-q] [-s] [-U] FILENAME1 FILENAME2
+
+ Check if two images have the same content. You can compare images with
+ different format or settings.
+
+ The format is probed unless you specify it by ``-f`` (used for
+ *FILENAME1*) and/or ``-F`` (used for *FILENAME2*) option.
+
+ By default, images with different size are considered identical if the larger
+ image contains only unallocated and/or zeroed sectors in the area after the end
+ of the other image. In addition, if any sector is not allocated in one image
+ and contains only zero bytes in the second one, it is evaluated as equal. You
+ can use Strict mode by specifying the ``-s`` option. When compare runs in
+ Strict mode, it fails in case image size differs or a sector is allocated in
+ one image and is not allocated in the second one.
+
+ By default, compare prints out a result message. This message displays
+ information that both images are same or the position of the first different
+ byte. In addition, result message can report different image size in case
+ Strict mode is used.
+
+ Compare exits with ``0`` in case the images are equal and with ``1``
+ in case the images differ. Other exit codes mean an error occurred during
+ execution and standard error output should contain an error message.
+ The following table sumarizes all exit codes of the compare subcommand:
+
+ 0
+ Images are identical
+ 1
+ Images differ
+ 2
+ Error on opening an image
+ 3
+ Error on checking a sector allocation
+ 4
+ Error on reading data
+
+.. option:: convert [--object OBJECTDEF] [--image-opts] [--target-image-opts] [-U] [-C] [-c] [-p] [-q] [-n] [-f FMT] [-t CACHE] [-T SRC_CACHE] [-O OUTPUT_FMT] [-B BACKING_FILE] [-o OPTIONS] [-l SNAPSHOT_PARAM] [-S SPARSE_SIZE] [-m NUM_COROUTINES] [-W] FILENAME [FILENAME2 [...]] OUTPUT_FILENAME
+
+ Convert the disk image *FILENAME* or a snapshot *SNAPSHOT_PARAM*
+ to disk image *OUTPUT_FILENAME* using format *OUTPUT_FMT*. It can
+ be optionally compressed (``-c`` option) or use any format specific
+ options like encryption (``-o`` option).
+
+ Only the formats ``qcow`` and ``qcow2`` support compression. The
+ compression is read-only. It means that if a compressed sector is
+ rewritten, then it is rewritten as uncompressed data.
+
+ Image conversion is also useful to get smaller image when using a
+ growable format such as ``qcow``: the empty sectors are detected and
+ suppressed from the destination image.
+
+ *SPARSE_SIZE* 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 *SPARSE_SIZE* is 0, the source will not be scanned for
+ unallocated or zero sectors, and the destination image will always be
+ fully allocated.
+
+ You can use the *BACKING_FILE* option to force the output image to be
+ created as a copy on write image of the specified base image; the
+ *BACKING_FILE* should have the same content as the input's base image,
+ however the path, image format, etc may differ.
+
+ If a relative path name is given, the backing file is looked up relative to
+ the directory containing *OUTPUT_FILENAME*.
+
+ If the ``-n`` option is specified, the target volume creation will be
+ skipped. This is useful for formats such as ``rbd`` if the target
+ volume has already been created with site specific options that cannot
+ be supplied through qemu-img.
+
+ Out of order writes can be enabled with ``-W`` to improve performance.
+ This is only recommended for preallocated devices like host devices or other
+ raw block devices. Out of order write does not work in combination with
+ creating compressed images.
+
+ *NUM_COROUTINES* specifies how many coroutines work in parallel during
+ the convert process (defaults to 8).
+
+.. option:: create [--object OBJECTDEF] [-q] [-f FMT] [-b BACKING_FILE] [-F BACKING_FMT] [-u] [-o OPTIONS] FILENAME [SIZE]
+
+ Create the new disk image *FILENAME* of size *SIZE* and format
+ *FMT*. Depending on the file format, you can add one or more *OPTIONS*
+ that enable additional features of this format.
+
+ If the option *BACKING_FILE* is specified, then the image will record
+ only the differences from *BACKING_FILE*. No size needs to be specified in
+ this case. *BACKING_FILE* will never be modified unless you use the
+ ``commit`` monitor command (or qemu-img commit).
+
+ If a relative path name is given, the backing file is looked up relative to
+ the directory containing *FILENAME*.
+
+ Note that a given backing file will be opened to check that it is valid. Use
+ the ``-u`` option to enable unsafe backing file mode, which means that the
+ image will be created even if the associated backing file cannot be opened. A
+ matching backing file must be created or additional options be used to make the
+ backing file specification valid when you want to use an image created this
+ way.
+
+ The size can also be specified using the *SIZE* option with ``-o``,
+ it doesn't need to be specified separately in this case.
+
+
+.. option:: dd [--image-opts] [-U] [-f FMT] [-O OUTPUT_FMT] [bs=BLOCK_SIZE] [count=BLOCKS] [skip=BLOCKS] if=INPUT of=OUTPUT
+
+ dd copies from *INPUT* file to *OUTPUT* file converting it from
+ *FMT* format to *OUTPUT_FMT* format.
+
+ The data is by default read and written using blocks of 512 bytes but can be
+ modified by specifying *BLOCK_SIZE*. If count=\ *BLOCKS* is specified
+ dd will stop reading input after reading *BLOCKS* input blocks.
+
+ The size syntax is similar to :manpage:`dd(1)`'s size syntax.
+
+.. option:: info [--object OBJECTDEF] [--image-opts] [-f FMT] [--output=OFMT] [--backing-chain] [-U] FILENAME
+
+ Give information about the disk image *FILENAME*. Use it in
+ particular to know the size reserved on disk which can be different
+ from the displayed size. If VM snapshots are stored in the disk image,
+ they are displayed too.
+
+ If a disk image has a backing file chain, information about each disk image in
+ the chain can be recursively enumerated by using the option ``--backing-chain``.
+
+ For instance, if you have an image chain like:
+
+ ::
+
+ base.qcow2 <- snap1.qcow2 <- snap2.qcow2
+
+ To enumerate information about each disk image in the above chain, starting from top to base, do:
+
+ ::
+
+ qemu-img info --backing-chain snap2.qcow2
+
+ The command can output in the format *OFMT* which is either ``human`` or
+ ``json``. The JSON output is an object of QAPI type ``ImageInfo``; with
+ ``--backing-chain``, it is an array of ``ImageInfo`` objects.
+
+ ``--output=human`` reports the following information (for every image in the
+ chain):
+
+ *image*
+ The image file name
+
+ *file format*
+ The image format
+
+ *virtual size*
+ The size of the guest disk
+
+ *disk size*
+ How much space the image file occupies on the host file system (may be
+ shown as 0 if this information is unavailable, e.g. because there is no
+ file system)
+
+ *cluster_size*
+ Cluster size of the image format, if applicable
+
+ *encrypted*
+ Whether the image is encrypted (only present if so)
+
+ *cleanly shut down*
+ This is shown as ``no`` if the image is dirty and will have to be
+ auto-repaired the next time it is opened in qemu.
+
+ *backing file*
+ The backing file name, if present
+
+ *backing file format*
+ The format of the backing file, if the image enforces it
+
+ *Snapshot list*
+ A list of all internal snapshots
+
+ *Format specific information*
+ Further information whose structure depends on the image format. This
+ section is a textual representation of the respective
+ ``ImageInfoSpecific*`` QAPI object (e.g. ``ImageInfoSpecificQCow2``
+ for qcow2 images).
+
+.. option:: map [--object OBJECTDEF] [--image-opts] [-f FMT] [--output=OFMT] [-U] FILENAME
+
+ Dump the metadata of image *FILENAME* and its backing file chain.
+ In particular, this commands dumps the allocation state of every sector
+ of *FILENAME*, together with the topmost file that allocates it in
+ the backing file chain.
+
+ Two option formats are possible. The default format (``human``)
+ only dumps known-nonzero areas of the file. Known-zero parts of the
+ file are omitted altogether, and likewise for parts that are not allocated
+ throughout the chain. ``qemu-img`` output will identify a file
+ from where the data can be read, and the offset in the file. Each line
+ will include four fields, the first three of which are hexadecimal
+ numbers. For example the first line of:
+
+ ::
+
+ Offset Length Mapped to File
+ 0 0x20000 0x50000 /tmp/overlay.qcow2
+ 0x100000 0x10000 0x95380000 /tmp/backing.qcow2
+
+ means that 0x20000 (131072) bytes starting at offset 0 in the image are
+ available in /tmp/overlay.qcow2 (opened in ``raw`` format) starting
+ at offset 0x50000 (327680). Data that is compressed, encrypted, or
+ otherwise not available in raw format will cause an error if ``human``
+ format is in use. Note that file names can include newlines, thus it is
+ not safe to parse this output format in scripts.
+
+ The alternative format ``json`` will return an array of dictionaries
+ in JSON format. It will include similar information in
+ the ``start``, ``length``, ``offset`` fields;
+ it will also include other more specific information:
+
+ - whether the sectors contain actual data or not (boolean field ``data``;
+ if false, the sectors are either unallocated or stored as optimized
+ all-zero clusters);
+ - whether the data is known to read as zero (boolean field ``zero``);
+ - in order to make the output shorter, the target file is expressed as
+ a ``depth``; for example, a depth of 2 refers to the backing file
+ of the backing file of *FILENAME*.
+
+ In JSON format, the ``offset`` field is optional; it is absent in
+ cases where ``human`` format would omit the entry or exit with an error.
+ If ``data`` is false and the ``offset`` field is present, the
+ corresponding sectors in the file are not yet in use, but they are
+ preallocated.
+
+ For more information, consult ``include/block/block.h`` in QEMU's
+ source code.
+
+.. option:: measure [--output=OFMT] [-O OUTPUT_FMT] [-o OPTIONS] [--size N | [--object OBJECTDEF] [--image-opts] [-f FMT] [-l SNAPSHOT_PARAM] FILENAME]
+
+ Calculate the file size required for a new image. This information
+ can be used to size logical volumes or SAN LUNs appropriately for
+ the image that will be placed in them. The values reported are
+ guaranteed to be large enough to fit the image. The command can
+ output in the format *OFMT* which is either ``human`` or ``json``.
+ The JSON output is an object of QAPI type ``BlockMeasureInfo``.
+
+ If the size *N* is given then act as if creating a new empty image file
+ using ``qemu-img create``. If *FILENAME* is given then act as if
+ converting an existing image file using ``qemu-img convert``. The format
+ of the new file is given by *OUTPUT_FMT* while the format of an existing
+ file is given by *FMT*.
+
+ A snapshot in an existing image can be specified using *SNAPSHOT_PARAM*.
+
+ The following fields are reported:
+
+ ::
+
+ required size: 524288
+ fully allocated size: 1074069504
+
+ The ``required size`` is the file size of the new image. It may be smaller
+ than the virtual disk size if the image format supports compact representation.
+
+ The ``fully allocated size`` is the file size of the new image once data has
+ been written to all sectors. This is the maximum size that the image file can
+ occupy with the exception of internal snapshots, dirty bitmaps, vmstate data,
+ and other advanced image format features.
+
+.. option:: snapshot [--object OBJECTDEF] [--image-opts] [-U] [-q] [-l | -a SNAPSHOT | -c SNAPSHOT | -d SNAPSHOT] FILENAME
+
+ List, apply, create or delete snapshots in image *FILENAME*.
+
+.. option:: rebase [--object OBJECTDEF] [--image-opts] [-U] [-q] [-f FMT] [-t CACHE] [-T SRC_CACHE] [-p] [-u] -b BACKING_FILE [-F BACKING_FMT] FILENAME
+
+ Changes the backing file of an image. Only the formats ``qcow2`` and
+ ``qed`` support changing the backing file.
+
+ The backing file is changed to *BACKING_FILE* and (if the image format of
+ *FILENAME* supports this) the backing file format is changed to
+ *BACKING_FMT*. If *BACKING_FILE* is specified as "" (the empty
+ string), then the image is rebased onto no backing file (i.e. it will exist
+ independently of any backing file).
+
+ If a relative path name is given, the backing file is looked up relative to
+ the directory containing *FILENAME*.
+
+ *CACHE* specifies the cache mode to be used for *FILENAME*, whereas
+ *SRC_CACHE* specifies the cache mode for reading backing files.
+
+ There are two different modes in which ``rebase`` can operate:
+
+ Safe mode
+ This is the default mode and performs a real rebase operation. The
+ new backing file may differ from the old one and qemu-img rebase
+ will take care of keeping the guest-visible content of *FILENAME*
+ unchanged.
+
+ In order to achieve this, any clusters that differ between
+ *BACKING_FILE* and the old backing file of *FILENAME* are merged
+ into *FILENAME* before actually changing the backing file.
+
+ Note that the safe mode is an expensive operation, comparable to
+ converting an image. It only works if the old backing file still
+ exists.
+
+ Unsafe mode
+ qemu-img uses the unsafe mode if ``-u`` is specified. In this
+ mode, only the backing file name and format of *FILENAME* is changed
+ without any checks on the file contents. The user must take care of
+ specifying the correct new backing file, or the guest-visible
+ content of the image will be corrupted.
+
+ This mode is useful for renaming or moving the backing file to
+ somewhere else. It can be used without an accessible old backing
+ file, i.e. you can use it to fix an image whose backing file has
+ already been moved/renamed.
+
+ You can use ``rebase`` to perform a "diff" operation on two
+ disk images. This can be useful when you have copied or cloned
+ a guest, and you want to get back to a thin image on top of a
+ template or base image.
+
+ Say that ``base.img`` has been cloned as ``modified.img`` by
+ copying it, and that the ``modified.img`` guest has run so there
+ are now some changes compared to ``base.img``. To construct a thin
+ image called ``diff.qcow2`` that contains just the differences, do:
+
+ ::
+
+ qemu-img create -f qcow2 -b modified.img diff.qcow2
+ qemu-img rebase -b base.img diff.qcow2
+
+ At this point, ``modified.img`` can be discarded, since
+ ``base.img + diff.qcow2`` contains the same information.
+
+.. option:: resize [--object OBJECTDEF] [--image-opts] [-f FMT] [--preallocation=PREALLOC] [-q] [--shrink] FILENAME [+ | -]SIZE
+
+ Change the disk image as if it had been created with *SIZE*.
+
+ Before using this command to shrink a disk image, you MUST use file system and
+ partitioning tools inside the VM to reduce allocated file systems and partition
+ sizes accordingly. Failure to do so will result in data loss!
+
+ When shrinking images, the ``--shrink`` option must be given. This informs
+ qemu-img that the user acknowledges all loss of data beyond the truncated
+ image's end.
+
+ After using this command to grow a disk image, you must use file system and
+ partitioning tools inside the VM to actually begin using the new space on the
+ device.
+
+ When growing an image, the ``--preallocation`` option may be used to specify
+ how the additional image area should be allocated on the host. See the format
+ description in the :ref:`notes` section which values are allowed. Using this
+ option may result in slightly more data being allocated than necessary.
+
+.. _notes:
+
+Notes
+-----
+
+Supported image file formats:
+
+``raw``
+
+ Raw disk image format (default). This format has the advantage of
+ being simple and easily exportable to all other emulators. If your
+ file system supports *holes* (for example in ext2 or ext3 on
+ Linux or NTFS on Windows), then only the written sectors will reserve
+ space. Use ``qemu-img info`` to know the real size used by the
+ image or ``ls -ls`` on Unix/Linux.
+
+ Supported options:
+
+ ``preallocation``
+ Preallocation mode (allowed values: ``off``, ``falloc``,
+ ``full``). ``falloc`` mode preallocates space for image by
+ calling ``posix_fallocate()``. ``full`` mode preallocates space
+ for image by writing data to underlying storage. This data may or
+ may not be zero, depending on the storage location.
+
+``qcow2``
+
+ QEMU image format, the most versatile format. Use it to have smaller
+ images (useful if your filesystem does not supports holes, for example
+ on Windows), optional AES encryption, zlib based compression and
+ support of multiple VM snapshots.
+
+ Supported options:
+
+ ``compat``
+ Determines the qcow2 version to use. ``compat=0.10`` uses the
+ traditional image format that can be read by any QEMU since 0.10.
+ ``compat=1.1`` enables image format extensions that only QEMU 1.1 and
+ newer understand (this is the default). Amongst others, this includes zero
+ clusters, which allow efficient copy-on-read for sparse images.
+
+ ``backing_file``
+ File name of a base image (see ``create`` subcommand)
+
+ ``backing_fmt``
+ Image format of the base image
+
+ ``encryption``
+ If this option is set to ``on``, the image is encrypted with
+ 128-bit AES-CBC.
+
+ The use of encryption in qcow and qcow2 images is considered to be
+ flawed by modern cryptography standards, suffering from a number
+ of design problems:
+
+ - The AES-CBC cipher is used with predictable initialization
+ vectors based on the sector number. This makes it vulnerable to
+ chosen plaintext attacks which can reveal the existence of
+ encrypted data.
+
+ - The user passphrase is directly used as the encryption key. A
+ poorly chosen or short passphrase will compromise the security
+ of the encryption.
+
+ - In the event of the passphrase being compromised there is no way
+ to change the passphrase to protect data in any qcow images. The
+ files must be cloned, using a different encryption passphrase in
+ the new file. The original file must then be securely erased
+ using a program like shred, though even this is ineffective with
+ many modern storage technologies.
+
+ - Initialization vectors used to encrypt sectors are based on the
+ guest virtual sector number, instead of the host physical
+ sector. When a disk image has multiple internal snapshots this
+ means that data in multiple physical sectors is encrypted with
+ the same initialization vector. With the CBC mode, this opens
+ the possibility of watermarking attacks if the attack can
+ collect multiple sectors encrypted with the same IV and some
+ predictable data. Having multiple qcow2 images with the same
+ passphrase also exposes this weakness since the passphrase is
+ directly used as the key.
+
+ Use of qcow / qcow2 encryption is thus strongly discouraged. Users are
+ recommended to use an alternative encryption technology such as the
+ Linux dm-crypt / LUKS system.
+
+ ``cluster_size``
+ Changes the qcow2 cluster size (must be between 512 and
+ 2M). Smaller cluster sizes can improve the image file size whereas
+ larger cluster sizes generally provide better performance.
+
+ ``preallocation``
+ Preallocation mode (allowed values: ``off``, ``metadata``,
+ ``falloc``, ``full``). An image with preallocated metadata is
+ initially larger but can improve performance when the image needs
+ to grow. ``falloc`` and ``full`` preallocations are like the same
+ options of ``raw`` format, but sets up metadata also.
+
+ ``lazy_refcounts``
+ If this option is set to ``on``, reference count updates are
+ postponed with the goal of avoiding metadata I/O and improving
+ performance. This is particularly interesting with
+ ``cache=writethrough`` which doesn't batch metadata
+ updates. The tradeoff is that after a host crash, the reference
+ count tables must be rebuilt, i.e. on the next open an (automatic)
+ ``qemu-img check -r all`` is required, which may take some time.
+
+ This option can only be enabled if ``compat=1.1`` is specified.
+
+ ``nocow``
+ If this option is set to ``on``, it will turn off COW of the file. It's
+ only valid on btrfs, no effect on other file systems.
+
+ Btrfs has low performance when hosting a VM image file, even more
+ when the guest on the VM also using btrfs as file system. Turning
+ off COW is a way to mitigate this bad performance. Generally there
+ are two ways to turn off COW on btrfs:
+
+ - Disable it by mounting with nodatacow, then all newly created files
+ will be NOCOW
+ - For an empty file, add the NOCOW file attribute. That's what this
+ option does.
+
+ Note: this option is only valid to new or empty files. If there is
+ an existing file which is COW and has data blocks already, it
+ couldn't be changed to NOCOW by setting ``nocow=on``. One can
+ issue ``lsattr filename`` to check if the NOCOW flag is set or not
+ (Capital 'C' is NOCOW flag).
+
+``Other``
+
+ QEMU also supports various other image file formats for
+ compatibility with older QEMU versions or other hypervisors,
+ including VMDK, VDI, VHD (vpc), VHDX, qcow1 and QED. For a full list
+ of supported formats see ``qemu-img --help``. For a more detailed
+ description of these formats, see the QEMU block drivers reference
+ documentation.
+
+ The main purpose of the block drivers for these formats is image
+ conversion. For running VMs, it is recommended to convert the disk
+ images to either raw or qcow2 in order to achieve good performance.
* disk_images_quickstart:: Quick start for disk image creation
* disk_images_snapshot_mode:: Snapshot mode
* vm_snapshots:: VM snapshots
-* qemu_img_invocation:: qemu-img Invocation
@end menu
@node disk_images_quickstart
size in kilobytes. You can add an @code{M} suffix to give the size in
megabytes and a @code{G} suffix for gigabytes.
-See @ref{qemu_img_invocation} for more information.
+@c When this document is converted to rst we should make this into
+@c a proper linked reference to the qemu-img documentation again:
+See the qemu-img invocation documentation for more information.
@node disk_images_snapshot_mode
@subsection Snapshot mode
state is not saved or restored properly (in particular USB).
@end itemize
-@node qemu_img_invocation
-@subsection @code{qemu-img} Invocation
-
-@include qemu-img.texi
-
@node pcsys_network
@section Network emulation
+++ /dev/null
-@example
-@c man begin SYNOPSIS
-@command{qemu-img} [@var{standard} @var{options}] @var{command} [@var{command} @var{options}]
-@c man end
-@end example
-
-@c man begin DESCRIPTION
-qemu-img allows you to create, convert and modify images offline. It can handle
-all image formats supported by QEMU.
-
-@b{Warning:} Never use qemu-img to modify images in use by a running virtual
-machine or any other process; this may destroy the image. Also, be aware that
-querying an image that is being modified by another process may encounter
-inconsistent state.
-@c man end
-
-@c man begin OPTIONS
-
-Standard options:
-@table @option
-@item -h, --help
-Display this help and exit
-@item -V, --version
-Display version information and exit
-@item -T, --trace [[enable=]@var{pattern}][,events=@var{file}][,file=@var{file}]
-@findex --trace
-@include qemu-option-trace.texi
-@end table
-
-The following commands are supported:
-
-@include qemu-img-cmds.texi
-
-Command parameters:
-@table @var
-
-@item filename
-is a disk image filename
-
-@item fmt
-is the disk image format. It is guessed automatically in most cases. See below
-for a description of the supported disk formats.
-
-@item size
-is the disk image size in bytes. Optional suffixes @code{k} or @code{K}
-(kilobyte, 1024) @code{M} (megabyte, 1024k) and @code{G} (gigabyte, 1024M)
-and T (terabyte, 1024G) are supported. @code{b} is ignored.
-
-@item output_filename
-is the destination disk image filename
-
-@item output_fmt
-is the destination format
-
-@item options
-is a comma separated list of format specific options in a
-name=value format. Use @code{-o ?} for an overview of the options supported
-by the used format or see the format descriptions below for details.
-
-@item snapshot_param
-is param used for internal snapshot, format is
-'snapshot.id=[ID],snapshot.name=[NAME]' or '[ID_OR_NAME]'
-
-@end table
-
-@table @option
-
-@item --object @var{objectdef}
-is a QEMU user creatable object definition. See the @code{qemu(1)} manual
-page for a description of the object properties. The most common object
-type is a @code{secret}, which is used to supply passwords and/or encryption
-keys.
-
-@item --image-opts
-Indicates that the source @var{filename} parameter is to be interpreted as a
-full option string, not a plain filename. This parameter is mutually
-exclusive with the @var{-f} parameter.
-
-@item --target-image-opts
-Indicates that the @var{output_filename} parameter(s) are to be interpreted as
-a full option string, not a plain filename. This parameter is mutually
-exclusive with the @var{-O} parameters. It is currently required to also use
-the @var{-n} parameter to skip image creation. This restriction may be relaxed
-in a future release.
-
-@item --force-share (-U)
-If specified, @code{qemu-img} will open the image in shared mode, allowing
-other QEMU processes to open it in write mode. For example, this can be used to
-get the image information (with 'info' subcommand) when the image is used by a
-running guest. Note that this could produce inconsistent results because of
-concurrent metadata changes, etc. This option is only allowed when opening
-images in read-only mode.
-
-@item --backing-chain
-will enumerate information about backing files in a disk image chain. Refer
-below for further description.
-
-@item -c
-indicates that target image must be compressed (qcow format only)
-
-@item -h
-with or without a command shows help and lists the supported formats
-
-@item -p
-display progress bar (compare, convert and rebase commands only).
-If the @var{-p} option is not used for a command that supports it, the
-progress is reported when the process receives a @code{SIGUSR1} or
-@code{SIGINFO} signal.
-
-@item -q
-Quiet mode - do not print any output (except errors). There's no progress bar
-in case both @var{-q} and @var{-p} options are used.
-
-@item -S @var{size}
-indicates the consecutive number of bytes that must contain only zeros
-for qemu-img to create a sparse image during conversion. This value is rounded
-down to the nearest 512 bytes. You may use the common size suffixes like
-@code{k} for kilobytes.
-
-@item -t @var{cache}
-specifies the cache mode that should be used with the (destination) file. See
-the documentation of the emulator's @code{-drive cache=...} option for allowed
-values.
-
-@item -T @var{src_cache}
-specifies the cache mode that should be used with the source file(s). See
-the documentation of the emulator's @code{-drive cache=...} option for allowed
-values.
-
-@end table
-
-Parameters to snapshot subcommand:
-
-@table @option
-
-@item snapshot
-is the name of the snapshot to create, apply or delete
-@item -a
-applies a snapshot (revert disk to saved state)
-@item -c
-creates a snapshot
-@item -d
-deletes a snapshot
-@item -l
-lists all snapshots in the given image
-@end table
-
-Parameters to compare subcommand:
-
-@table @option
-
-@item -f
-First image format
-@item -F
-Second image format
-@item -s
-Strict mode - fail on different image size or sector allocation
-@end table
-
-Parameters to convert subcommand:
-
-@table @option
-
-@item -n
-Skip the creation of the target volume
-@item -m
-Number of parallel coroutines for the convert process
-@item -W
-Allow out-of-order writes to the destination. This option improves performance,
-but is only recommended for preallocated devices like host devices or other
-raw block devices.
-@item -C
-Try to use copy offloading to move data from source image to target. This may
-improve performance if the data is remote, such as with NFS or iSCSI backends,
-but will not automatically sparsify zero sectors, and may result in a fully
-allocated target image depending on the host support for getting allocation
-information.
-@item --salvage
-Try to ignore I/O errors when reading. Unless in quiet mode (@code{-q}), errors
-will still be printed. Areas that cannot be read from the source will be
-treated as containing only zeroes.
-@end table
-
-Parameters to dd subcommand:
-
-@table @option
-
-@item bs=@var{block_size}
-defines the block size
-@item count=@var{blocks}
-sets the number of input blocks to copy
-@item if=@var{input}
-sets the input file
-@item of=@var{output}
-sets the output file
-@item skip=@var{blocks}
-sets the number of input blocks to skip
-@end table
-
-Command description:
-
-@table @option
-
-@item amend [--object @var{objectdef}] [--image-opts] [-p] [-q] [-f @var{fmt}] [-t @var{cache}] -o @var{options} @var{filename}
-
-Amends the image format specific @var{options} for the image file
-@var{filename}. Not all file formats support this operation.
-
-@item bench [-c @var{count}] [-d @var{depth}] [-f @var{fmt}] [--flush-interval=@var{flush_interval}] [-n] [-i @var{aio}] [--no-drain] [-o @var{offset}] [--pattern=@var{pattern}] [-q] [-s @var{buffer_size}] [-S @var{step_size}] [-t @var{cache}] [-w] [-U] @var{filename}
-
-Run a simple sequential I/O benchmark on the specified image. If @code{-w} is
-specified, a write test is performed, otherwise a read test is performed.
-
-A total number of @var{count} I/O requests is performed, each @var{buffer_size}
-bytes in size, and with @var{depth} requests in parallel. The first request
-starts at the position given by @var{offset}, each following request increases
-the current position by @var{step_size}. If @var{step_size} is not given,
-@var{buffer_size} is used for its value.
-
-If @var{flush_interval} is specified for a write test, the request queue is
-drained and a flush is issued before new writes are made whenever the number of
-remaining requests is a multiple of @var{flush_interval}. If additionally
-@code{--no-drain} is specified, a flush is issued without draining the request
-queue first.
-
-If @code{-n} is specified, the native AIO backend is used if possible. On
-Linux, this option only works if @code{-t none} or @code{-t directsync} is
-specified as well.
-
-If @code{-i} is specified, aio option can be used to specify different AIO
-backends: @var{threads}, @var{native} or @var{io_uring}.
-
-For write tests, by default a buffer filled with zeros is written. This can be
-overridden with a pattern byte specified by @var{pattern}.
-
-@item check [--object @var{objectdef}] [--image-opts] [-q] [-f @var{fmt}] [--output=@var{ofmt}] [-r [leaks | all]] [-T @var{src_cache}] [-U] @var{filename}
-
-Perform a consistency check on the disk image @var{filename}. The command can
-output in the format @var{ofmt} which is either @code{human} or @code{json}.
-The JSON output is an object of QAPI type @code{ImageCheck}.
-
-If @code{-r} is specified, qemu-img tries to repair any inconsistencies found
-during the check. @code{-r leaks} repairs only cluster leaks, whereas
-@code{-r all} fixes all kinds of errors, with a higher risk of choosing the
-wrong fix or hiding corruption that has already occurred.
-
-Only the formats @code{qcow2}, @code{qed} and @code{vdi} support
-consistency checks.
-
-In case the image does not have any inconsistencies, check exits with @code{0}.
-Other exit codes indicate the kind of inconsistency found or if another error
-occurred. The following table summarizes all exit codes of the check subcommand:
-
-@table @option
-
-@item 0
-Check completed, the image is (now) consistent
-@item 1
-Check not completed because of internal errors
-@item 2
-Check completed, image is corrupted
-@item 3
-Check completed, image has leaked clusters, but is not corrupted
-@item 63
-Checks are not supported by the image format
-
-@end table
-
-If @code{-r} is specified, exit codes representing the image state refer to the
-state after (the attempt at) repairing it. That is, a successful @code{-r all}
-will yield the exit code 0, independently of the image state before.
-
-@item commit [--object @var{objectdef}] [--image-opts] [-q] [-f @var{fmt}] [-t @var{cache}] [-b @var{base}] [-d] [-p] @var{filename}
-
-Commit the changes recorded in @var{filename} in its base image or backing file.
-If the backing file is smaller than the snapshot, then the backing file will be
-resized to be the same size as the snapshot. If the snapshot is smaller than
-the backing file, the backing file will not be truncated. If you want the
-backing file to match the size of the smaller snapshot, you can safely truncate
-it yourself once the commit operation successfully completes.
-
-The image @var{filename} is emptied after the operation has succeeded. If you do
-not need @var{filename} afterwards and intend to drop it, you may skip emptying
-@var{filename} by specifying the @code{-d} flag.
-
-If the backing chain of the given image file @var{filename} has more than one
-layer, the backing file into which the changes will be committed may be
-specified as @var{base} (which has to be part of @var{filename}'s backing
-chain). If @var{base} is not specified, the immediate backing file of the top
-image (which is @var{filename}) will be used. Note that after a commit operation
-all images between @var{base} and the top image will be invalid and may return
-garbage data when read. For this reason, @code{-b} implies @code{-d} (so that
-the top image stays valid).
-
-@item compare [--object @var{objectdef}] [--image-opts] [-f @var{fmt}] [-F @var{fmt}] [-T @var{src_cache}] [-p] [-q] [-s] [-U] @var{filename1} @var{filename2}
-
-Check if two images have the same content. You can compare images with
-different format or settings.
-
-The format is probed unless you specify it by @var{-f} (used for
-@var{filename1}) and/or @var{-F} (used for @var{filename2}) option.
-
-By default, images with different size are considered identical if the larger
-image contains only unallocated and/or zeroed sectors in the area after the end
-of the other image. In addition, if any sector is not allocated in one image
-and contains only zero bytes in the second one, it is evaluated as equal. You
-can use Strict mode by specifying the @var{-s} option. When compare runs in
-Strict mode, it fails in case image size differs or a sector is allocated in
-one image and is not allocated in the second one.
-
-By default, compare prints out a result message. This message displays
-information that both images are same or the position of the first different
-byte. In addition, result message can report different image size in case
-Strict mode is used.
-
-Compare exits with @code{0} in case the images are equal and with @code{1}
-in case the images differ. Other exit codes mean an error occurred during
-execution and standard error output should contain an error message.
-The following table sumarizes all exit codes of the compare subcommand:
-
-@table @option
-
-@item 0
-Images are identical
-@item 1
-Images differ
-@item 2
-Error on opening an image
-@item 3
-Error on checking a sector allocation
-@item 4
-Error on reading data
-
-@end table
-
-@item convert [--object @var{objectdef}] [--image-opts] [--target-image-opts] [-U] [-C] [-c] [-p] [-q] [-n] [-f @var{fmt}] [-t @var{cache}] [-T @var{src_cache}] [-O @var{output_fmt}] [-B @var{backing_file}] [-o @var{options}] [-l @var{snapshot_param}] [-S @var{sparse_size}] [-m @var{num_coroutines}] [-W] @var{filename} [@var{filename2} [...]] @var{output_filename}
-
-Convert the disk image @var{filename} or a snapshot @var{snapshot_param}
-to disk image @var{output_filename} using format @var{output_fmt}. It can be optionally compressed (@code{-c}
-option) or use any format specific options like encryption (@code{-o} option).
-
-Only the formats @code{qcow} and @code{qcow2} support compression. The
-compression is read-only. It means that if a compressed sector is
-rewritten, then it is rewritten as uncompressed data.
-
-Image conversion is also useful to get smaller image when using a
-growable format such as @code{qcow}: the empty sectors are detected and
-suppressed from the destination image.
-
-@var{sparse_size} 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 @var{sparse_size} is 0, the source will not be scanned for
-unallocated or zero sectors, and the destination image will always be
-fully allocated.
-
-You can use the @var{backing_file} option to force the output image to be
-created as a copy on write image of the specified base image; the
-@var{backing_file} should have the same content as the input's base image,
-however the path, image format, etc may differ.
-
-If a relative path name is given, the backing file is looked up relative to
-the directory containing @var{output_filename}.
-
-If the @code{-n} option is specified, the target volume creation will be
-skipped. This is useful for formats such as @code{rbd} if the target
-volume has already been created with site specific options that cannot
-be supplied through qemu-img.
-
-Out of order writes can be enabled with @code{-W} to improve performance.
-This is only recommended for preallocated devices like host devices or other
-raw block devices. Out of order write does not work in combination with
-creating compressed images.
-
-@var{num_coroutines} specifies how many coroutines work in parallel during
-the convert process (defaults to 8).
-
-@item create [--object @var{objectdef}] [-q] [-f @var{fmt}] [-b @var{backing_file}] [-F @var{backing_fmt}] [-u] [-o @var{options}] @var{filename} [@var{size}]
-
-Create the new disk image @var{filename} of size @var{size} and format
-@var{fmt}. Depending on the file format, you can add one or more @var{options}
-that enable additional features of this format.
-
-If the option @var{backing_file} is specified, then the image will record
-only the differences from @var{backing_file}. No size needs to be specified in
-this case. @var{backing_file} will never be modified unless you use the
-@code{commit} monitor command (or qemu-img commit).
-
-If a relative path name is given, the backing file is looked up relative to
-the directory containing @var{filename}.
-
-Note that a given backing file will be opened to check that it is valid. Use
-the @code{-u} option to enable unsafe backing file mode, which means that the
-image will be created even if the associated backing file cannot be opened. A
-matching backing file must be created or additional options be used to make the
-backing file specification valid when you want to use an image created this
-way.
-
-The size can also be specified using the @var{size} option with @code{-o},
-it doesn't need to be specified separately in this case.
-
-@item dd [--image-opts] [-U] [-f @var{fmt}] [-O @var{output_fmt}] [bs=@var{block_size}] [count=@var{blocks}] [skip=@var{blocks}] if=@var{input} of=@var{output}
-
-Dd copies from @var{input} file to @var{output} file converting it from
-@var{fmt} format to @var{output_fmt} format.
-
-The data is by default read and written using blocks of 512 bytes but can be
-modified by specifying @var{block_size}. If count=@var{blocks} is specified
-dd will stop reading input after reading @var{blocks} input blocks.
-
-The size syntax is similar to dd(1)'s size syntax.
-
-@item info [--object @var{objectdef}] [--image-opts] [-f @var{fmt}] [--output=@var{ofmt}] [--backing-chain] [-U] @var{filename}
-
-Give information about the disk image @var{filename}. Use it in
-particular to know the size reserved on disk which can be different
-from the displayed size. If VM snapshots are stored in the disk image,
-they are displayed too.
-
-If a disk image has a backing file chain, information about each disk image in
-the chain can be recursively enumerated by using the option @code{--backing-chain}.
-
-For instance, if you have an image chain like:
-
-@example
-base.qcow2 <- snap1.qcow2 <- snap2.qcow2
-@end example
-
-To enumerate information about each disk image in the above chain, starting from top to base, do:
-
-@example
-qemu-img info --backing-chain snap2.qcow2
-@end example
-
-The command can output in the format @var{ofmt} which is either @code{human} or
-@code{json}. The JSON output is an object of QAPI type @code{ImageInfo}; with
-@code{--backing-chain}, it is an array of @code{ImageInfo} objects.
-
-@code{--output=human} reports the following information (for every image in the
-chain):
-@table @var
-@item image
-The image file name
-
-@item file format
-The image format
-
-@item virtual size
-The size of the guest disk
-
-@item disk size
-How much space the image file occupies on the host file system (may be shown as
-0 if this information is unavailable, e.g. because there is no file system)
-
-@item cluster_size
-Cluster size of the image format, if applicable
-
-@item encrypted
-Whether the image is encrypted (only present if so)
-
-@item cleanly shut down
-This is shown as @code{no} if the image is dirty and will have to be
-auto-repaired the next time it is opened in qemu.
-
-@item backing file
-The backing file name, if present
-
-@item backing file format
-The format of the backing file, if the image enforces it
-
-@item Snapshot list
-A list of all internal snapshots
-
-@item Format specific information
-Further information whose structure depends on the image format. This section
-is a textual representation of the respective @code{ImageInfoSpecific*} QAPI
-object (e.g. @code{ImageInfoSpecificQCow2} for qcow2 images).
-@end table
-
-@item map [--object @var{objectdef}] [--image-opts] [-f @var{fmt}] [--output=@var{ofmt}] [-U] @var{filename}
-
-Dump the metadata of image @var{filename} and its backing file chain.
-In particular, this commands dumps the allocation state of every sector
-of @var{filename}, together with the topmost file that allocates it in
-the backing file chain.
-
-Two option formats are possible. The default format (@code{human})
-only dumps known-nonzero areas of the file. Known-zero parts of the
-file are omitted altogether, and likewise for parts that are not allocated
-throughout the chain. @command{qemu-img} output will identify a file
-from where the data can be read, and the offset in the file. Each line
-will include four fields, the first three of which are hexadecimal
-numbers. For example the first line of:
-@example
-Offset Length Mapped to File
-0 0x20000 0x50000 /tmp/overlay.qcow2
-0x100000 0x10000 0x95380000 /tmp/backing.qcow2
-@end example
-@noindent
-means that 0x20000 (131072) bytes starting at offset 0 in the image are
-available in /tmp/overlay.qcow2 (opened in @code{raw} format) starting
-at offset 0x50000 (327680). Data that is compressed, encrypted, or
-otherwise not available in raw format will cause an error if @code{human}
-format is in use. Note that file names can include newlines, thus it is
-not safe to parse this output format in scripts.
-
-The alternative format @code{json} will return an array of dictionaries
-in JSON format. It will include similar information in
-the @code{start}, @code{length}, @code{offset} fields;
-it will also include other more specific information:
-@itemize @minus
-@item
-whether the sectors contain actual data or not (boolean field @code{data};
-if false, the sectors are either unallocated or stored as optimized
-all-zero clusters);
-
-@item
-whether the data is known to read as zero (boolean field @code{zero});
-
-@item
-in order to make the output shorter, the target file is expressed as
-a @code{depth}; for example, a depth of 2 refers to the backing file
-of the backing file of @var{filename}.
-@end itemize
-
-In JSON format, the @code{offset} field is optional; it is absent in
-cases where @code{human} format would omit the entry or exit with an error.
-If @code{data} is false and the @code{offset} field is present, the
-corresponding sectors in the file are not yet in use, but they are
-preallocated.
-
-For more information, consult @file{include/block/block.h} in QEMU's
-source code.
-
-@item measure [--output=@var{ofmt}] [-O @var{output_fmt}] [-o @var{options}] [--size @var{N} | [--object @var{objectdef}] [--image-opts] [-f @var{fmt}] [-l @var{snapshot_param}] @var{filename}]
-
-Calculate the file size required for a new image. This information can be used
-to size logical volumes or SAN LUNs appropriately for the image that will be
-placed in them. The values reported are guaranteed to be large enough to fit
-the image. The command can output in the format @var{ofmt} which is either
-@code{human} or @code{json}. The JSON output is an object of QAPI type
-@code{BlockMeasureInfo}.
-
-If the size @var{N} is given then act as if creating a new empty image file
-using @command{qemu-img create}. If @var{filename} is given then act as if
-converting an existing image file using @command{qemu-img convert}. The format
-of the new file is given by @var{output_fmt} while the format of an existing
-file is given by @var{fmt}.
-
-A snapshot in an existing image can be specified using @var{snapshot_param}.
-
-The following fields are reported:
-@example
-required size: 524288
-fully allocated size: 1074069504
-@end example
-
-The @code{required size} is the file size of the new image. It may be smaller
-than the virtual disk size if the image format supports compact representation.
-
-The @code{fully allocated size} is the file size of the new image once data has
-been written to all sectors. This is the maximum size that the image file can
-occupy with the exception of internal snapshots, dirty bitmaps, vmstate data,
-and other advanced image format features.
-
-@item snapshot [--object @var{objectdef}] [--image-opts] [-U] [-q] [-l | -a @var{snapshot} | -c @var{snapshot} | -d @var{snapshot}] @var{filename}
-
-List, apply, create or delete snapshots in image @var{filename}.
-
-@item rebase [--object @var{objectdef}] [--image-opts] [-U] [-q] [-f @var{fmt}] [-t @var{cache}] [-T @var{src_cache}] [-p] [-u] -b @var{backing_file} [-F @var{backing_fmt}] @var{filename}
-
-Changes the backing file of an image. Only the formats @code{qcow2} and
-@code{qed} support changing the backing file.
-
-The backing file is changed to @var{backing_file} and (if the image format of
-@var{filename} supports this) the backing file format is changed to
-@var{backing_fmt}. If @var{backing_file} is specified as ``'' (the empty
-string), then the image is rebased onto no backing file (i.e. it will exist
-independently of any backing file).
-
-If a relative path name is given, the backing file is looked up relative to
-the directory containing @var{filename}.
-
-@var{cache} specifies the cache mode to be used for @var{filename}, whereas
-@var{src_cache} specifies the cache mode for reading backing files.
-
-There are two different modes in which @code{rebase} can operate:
-@table @option
-@item Safe mode
-This is the default mode and performs a real rebase operation. The new backing
-file may differ from the old one and qemu-img rebase will take care of keeping
-the guest-visible content of @var{filename} unchanged.
-
-In order to achieve this, any clusters that differ between @var{backing_file}
-and the old backing file of @var{filename} are merged into @var{filename}
-before actually changing the backing file.
-
-Note that the safe mode is an expensive operation, comparable to converting
-an image. It only works if the old backing file still exists.
-
-@item Unsafe mode
-qemu-img uses the unsafe mode if @code{-u} is specified. In this mode, only the
-backing file name and format of @var{filename} is changed without any checks
-on the file contents. The user must take care of specifying the correct new
-backing file, or the guest-visible content of the image will be corrupted.
-
-This mode is useful for renaming or moving the backing file to somewhere else.
-It can be used without an accessible old backing file, i.e. you can use it to
-fix an image whose backing file has already been moved/renamed.
-@end table
-
-You can use @code{rebase} to perform a ``diff'' operation on two
-disk images. This can be useful when you have copied or cloned
-a guest, and you want to get back to a thin image on top of a
-template or base image.
-
-Say that @code{base.img} has been cloned as @code{modified.img} by
-copying it, and that the @code{modified.img} guest has run so there
-are now some changes compared to @code{base.img}. To construct a thin
-image called @code{diff.qcow2} that contains just the differences, do:
-
-@example
-qemu-img create -f qcow2 -b modified.img diff.qcow2
-qemu-img rebase -b base.img diff.qcow2
-@end example
-
-At this point, @code{modified.img} can be discarded, since
-@code{base.img + diff.qcow2} contains the same information.
-
-@item resize [--object @var{objectdef}] [--image-opts] [-f @var{fmt}] [--preallocation=@var{prealloc}] [-q] [--shrink] @var{filename} [+ | -]@var{size}
-
-Change the disk image as if it had been created with @var{size}.
-
-Before using this command to shrink a disk image, you MUST use file system and
-partitioning tools inside the VM to reduce allocated file systems and partition
-sizes accordingly. Failure to do so will result in data loss!
-
-When shrinking images, the @code{--shrink} option must be given. This informs
-qemu-img that the user acknowledges all loss of data beyond the truncated
-image's end.
-
-After using this command to grow a disk image, you must use file system and
-partitioning tools inside the VM to actually begin using the new space on the
-device.
-
-When growing an image, the @code{--preallocation} option may be used to specify
-how the additional image area should be allocated on the host. See the format
-description in the @code{NOTES} section which values are allowed. Using this
-option may result in slightly more data being allocated than necessary.
-
-@end table
-@c man end
-
-@ignore
-@c man begin NOTES
-Supported image file formats:
-
-@table @option
-@item raw
-
-Raw disk image format (default). This format has the advantage of
-being simple and easily exportable to all other emulators. If your
-file system supports @emph{holes} (for example in ext2 or ext3 on
-Linux or NTFS on Windows), then only the written sectors will reserve
-space. Use @code{qemu-img info} to know the real size used by the
-image or @code{ls -ls} on Unix/Linux.
-
-Supported options:
-@table @code
-@item preallocation
-Preallocation mode (allowed values: @code{off}, @code{falloc}, @code{full}).
-@code{falloc} mode preallocates space for image by calling posix_fallocate().
-@code{full} mode preallocates space for image by writing data to underlying
-storage. This data may or may not be zero, depending on the storage location.
-@end table
-
-@item qcow2
-QEMU image format, the most versatile format. Use it to have smaller
-images (useful if your filesystem does not supports holes, for example
-on Windows), optional AES encryption, zlib based compression and
-support of multiple VM snapshots.
-
-Supported options:
-@table @code
-@item compat
-Determines the qcow2 version to use. @code{compat=0.10} uses the
-traditional image format that can be read by any QEMU since 0.10.
-@code{compat=1.1} enables image format extensions that only QEMU 1.1 and
-newer understand (this is the default). Amongst others, this includes zero
-clusters, which allow efficient copy-on-read for sparse images.
-
-@item backing_file
-File name of a base image (see @option{create} subcommand)
-@item backing_fmt
-Image format of the base image
-@item encryption
-If this option is set to @code{on}, the image is encrypted with 128-bit AES-CBC.
-
-The use of encryption in qcow and qcow2 images is considered to be flawed by
-modern cryptography standards, suffering from a number of design problems:
-
-@itemize @minus
-@item
-The AES-CBC cipher is used with predictable initialization vectors based
-on the sector number. This makes it vulnerable to chosen plaintext attacks
-which can reveal the existence of encrypted data.
-@item
-The user passphrase is directly used as the encryption key. A poorly
-chosen or short passphrase will compromise the security of the encryption.
-@item
-In the event of the passphrase being compromised there is no way to
-change the passphrase to protect data in any qcow images. The files must
-be cloned, using a different encryption passphrase in the new file. The
-original file must then be securely erased using a program like shred,
-though even this is ineffective with many modern storage technologies.
-@item
-Initialization vectors used to encrypt sectors are based on the
-guest virtual sector number, instead of the host physical sector. When
-a disk image has multiple internal snapshots this means that data in
-multiple physical sectors is encrypted with the same initialization
-vector. With the CBC mode, this opens the possibility of watermarking
-attacks if the attack can collect multiple sectors encrypted with the
-same IV and some predictable data. Having multiple qcow2 images with
-the same passphrase also exposes this weakness since the passphrase
-is directly used as the key.
-@end itemize
-
-Use of qcow / qcow2 encryption is thus strongly discouraged. Users are
-recommended to use an alternative encryption technology such as the
-Linux dm-crypt / LUKS system.
-
-@item cluster_size
-Changes the qcow2 cluster size (must be between 512 and 2M). Smaller cluster
-sizes can improve the image file size whereas larger cluster sizes generally
-provide better performance.
-
-@item preallocation
-Preallocation mode (allowed values: @code{off}, @code{metadata}, @code{falloc},
-@code{full}). An image with preallocated metadata is initially larger but can
-improve performance when the image needs to grow. @code{falloc} and @code{full}
-preallocations are like the same options of @code{raw} format, but sets up
-metadata also.
-
-@item lazy_refcounts
-If this option is set to @code{on}, reference count updates are postponed with
-the goal of avoiding metadata I/O and improving performance. This is
-particularly interesting with @option{cache=writethrough} which doesn't batch
-metadata updates. The tradeoff is that after a host crash, the reference count
-tables must be rebuilt, i.e. on the next open an (automatic) @code{qemu-img
-check -r all} is required, which may take some time.
-
-This option can only be enabled if @code{compat=1.1} is specified.
-
-@item nocow
-If this option is set to @code{on}, it will turn off COW of the file. It's only
-valid on btrfs, no effect on other file systems.
-
-Btrfs has low performance when hosting a VM image file, even more when the guest
-on the VM also using btrfs as file system. Turning off COW is a way to mitigate
-this bad performance. Generally there are two ways to turn off COW on btrfs:
-a) Disable it by mounting with nodatacow, then all newly created files will be
-NOCOW. b) For an empty file, add the NOCOW file attribute. That's what this option
-does.
-
-Note: this option is only valid to new or empty files. If there is an existing
-file which is COW and has data blocks already, it couldn't be changed to NOCOW
-by setting @code{nocow=on}. One can issue @code{lsattr filename} to check if
-the NOCOW flag is set or not (Capital 'C' is NOCOW flag).
-
-@end table
-
-@item Other
-QEMU also supports various other image file formats for compatibility with
-older QEMU versions or other hypervisors, including VMDK, VDI, VHD (vpc), VHDX,
-qcow1 and QED. For a full list of supported formats see @code{qemu-img --help}.
-For a more detailed description of these formats, see the QEMU Emulation User
-Documentation.
-
-The main purpose of the block drivers for these formats is image conversion.
-For running VMs, it is recommended to convert the disk images to either raw or
-qcow2 in order to achieve good performance.
-@end table
-
-
-@c man end
-
-@setfilename qemu-img
-@settitle QEMU disk image utility
-
-@c man begin SEEALSO
-The HTML documentation of QEMU for more precise information and Linux
-user mode emulator invocation.
-@c man end
-
-@c man begin AUTHOR
-Fabrice Bellard
-@c man end
-
-@end ignore