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.\" ========================================================================
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.IX Title "QEMU-IMG 1"
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.TH QEMU-IMG 1 "2012-01-11" " " " "
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.\" For nroff, turn off justification. Always turn off hyphenation; it makes
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.\" way too many mistakes in technical documents.
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qemu\-img \- QEMU disk image utility
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.IX Header "SYNOPSIS"
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usage: qemu-img command [command options]
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The following commands are supported:
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.IP "\fBcheck [\-f\fR \fIfmt\fR\fB]\fR \fIfilename\fR" 4
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.IX Item "check [-f fmt] filename"
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.IP "\fBcreate [\-f\fR \fIfmt\fR\fB] [\-o\fR \fIoptions\fR\fB]\fR \fIfilename\fR \fB[\fR\fIsize\fR\fB]\fR" 4
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.IX Item "create [-f fmt] [-o options] filename [size]"
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.IP "\fBcommit [\-f\fR \fIfmt\fR\fB]\fR \fIfilename\fR" 4
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.IX Item "commit [-f fmt] filename"
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.IP "\fBconvert [\-c] [\-p] [\-f\fR \fIfmt\fR\fB] [\-O\fR \fIoutput_fmt\fR\fB] [\-o\fR \fIoptions\fR\fB] [\-s\fR \fIsnapshot_name\fR\fB] [\-S\fR \fIsparse_size\fR\fB]\fR \fIfilename\fR \fB[\fR\fIfilename2\fR \fB[...]]\fR \fIoutput_filename\fR" 4
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.IX Item "convert [-c] [-p] [-f fmt] [-O output_fmt] [-o options] [-s snapshot_name] [-S sparse_size] filename [filename2 [...]] output_filename"
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.IP "\fBinfo [\-f\fR \fIfmt\fR\fB]\fR \fIfilename\fR" 4
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.IX Item "info [-f fmt] filename"
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.IP "\fBsnapshot [\-l | \-a\fR \fIsnapshot\fR \fB| \-c\fR \fIsnapshot\fR \fB| \-d\fR \fIsnapshot\fR\fB]\fR \fIfilename\fR" 4
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.IX Item "snapshot [-l | -a snapshot | -c snapshot | -d snapshot] filename"
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.IP "\fBrebase [\-f\fR \fIfmt\fR\fB] [\-p] [\-u] \-b\fR \fIbacking_file\fR \fB[\-F\fR \fIbacking_fmt\fR\fB]\fR \fIfilename\fR" 4
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.IX Item "rebase [-f fmt] [-p] [-u] -b backing_file [-F backing_fmt] filename"
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.IP "\fBresize\fR \fIfilename\fR \fB[+ | \-]\fR\fIsize\fR" 4
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.IX Item "resize filename [+ | -]size"
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.IP "\fIfilename\fR" 4
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\& is a disk image filename
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is the disk image format. It is guessed automatically in most cases. See below
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for a description of the supported disk formats.
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is the disk image size in bytes. Optional suffixes \f(CW\*(C`k\*(C'\fR or \f(CW\*(C`K\*(C'\fR
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(kilobyte, 1024) \f(CW\*(C`M\*(C'\fR (megabyte, 1024k) and \f(CW\*(C`G\*(C'\fR (gigabyte, 1024M)
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and T (terabyte, 1024G) are supported. \f(CW\*(C`b\*(C'\fR is ignored.
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.IP "\fIoutput_filename\fR" 4
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.IX Item "output_filename"
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is the destination disk image filename
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.IP "\fIoutput_fmt\fR" 4
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.IX Item "output_fmt"
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\& is the destination format
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.IP "\fIoptions\fR" 4
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is a comma separated list of format specific options in a
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name=value format. Use \f(CW\*(C`\-o ?\*(C'\fR for an overview of the options supported
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by the used format or see the format descriptions below for details.
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indicates that target image must be compressed (qcow format only)
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with or without a command shows help and lists the supported formats
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display progress bar (convert and rebase commands only)
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.IP "\fI\-S\fR \fIsize\fR" 4
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indicates the consecutive number of bytes that must contain only zeros
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for qemu-img to create a sparse image during conversion. This value is rounded
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down to the nearest 512 bytes. You may use the common size suffixes like
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\&\f(CW\*(C`k\*(C'\fR for kilobytes.
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Parameters to snapshot subcommand:
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.IP "\fBsnapshot\fR" 4
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is the name of the snapshot to create, apply or delete
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applies a snapshot (revert disk to saved state)
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lists all snapshots in the given image
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.IP "\fBcheck [\-f\fR \fIfmt\fR\fB]\fR \fIfilename\fR" 4
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.IX Item "check [-f fmt] filename"
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Perform a consistency check on the disk image \fIfilename\fR.
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Only the formats \f(CW\*(C`qcow2\*(C'\fR, \f(CW\*(C`qed\*(C'\fR and \f(CW\*(C`vdi\*(C'\fR support
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.IP "\fBcreate [\-f\fR \fIfmt\fR\fB] [\-o\fR \fIoptions\fR\fB]\fR \fIfilename\fR \fB[\fR\fIsize\fR\fB]\fR" 4
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.IX Item "create [-f fmt] [-o options] filename [size]"
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Create the new disk image \fIfilename\fR of size \fIsize\fR and format
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\&\fIfmt\fR. Depending on the file format, you can add one or more \fIoptions\fR
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that enable additional features of this format.
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If the option \fIbacking_file\fR is specified, then the image will record
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only the differences from \fIbacking_file\fR. No size needs to be specified in
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this case. \fIbacking_file\fR will never be modified unless you use the
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\&\f(CW\*(C`commit\*(C'\fR monitor command (or qemu-img commit).
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The size can also be specified using the \fIsize\fR option with \f(CW\*(C`\-o\*(C'\fR,
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it doesn't need to be specified separately in this case.
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.IP "\fBcommit [\-f\fR \fIfmt\fR\fB]\fR \fIfilename\fR" 4
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.IX Item "commit [-f fmt] filename"
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Commit the changes recorded in \fIfilename\fR in its base image.
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.IP "\fBconvert [\-c] [\-p] [\-f\fR \fIfmt\fR\fB] [\-O\fR \fIoutput_fmt\fR\fB] [\-o\fR \fIoptions\fR\fB] [\-s\fR \fIsnapshot_name\fR\fB] [\-S\fR \fIsparse_size\fR\fB]\fR \fIfilename\fR \fB[\fR\fIfilename2\fR \fB[...]]\fR \fIoutput_filename\fR" 4
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.IX Item "convert [-c] [-p] [-f fmt] [-O output_fmt] [-o options] [-s snapshot_name] [-S sparse_size] filename [filename2 [...]] output_filename"
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Convert the disk image \fIfilename\fR or a snapshot \fIsnapshot_name\fR to disk image \fIoutput_filename\fR
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using format \fIoutput_fmt\fR. It can be optionally compressed (\f(CW\*(C`\-c\*(C'\fR
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option) or use any format specific options like encryption (\f(CW\*(C`\-o\*(C'\fR option).
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Only the formats \f(CW\*(C`qcow\*(C'\fR and \f(CW\*(C`qcow2\*(C'\fR support compression. The
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compression is read-only. It means that if a compressed sector is
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rewritten, then it is rewritten as uncompressed data.
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Image conversion is also useful to get smaller image when using a
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growable format such as \f(CW\*(C`qcow\*(C'\fR or \f(CW\*(C`cow\*(C'\fR: the empty sectors
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are detected and suppressed from the destination image.
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You can use the \fIbacking_file\fR option to force the output image to be
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created as a copy on write image of the specified base image; the
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\&\fIbacking_file\fR should have the same content as the input's base image,
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however the path, image format, etc may differ.
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.IP "\fBinfo [\-f\fR \fIfmt\fR\fB]\fR \fIfilename\fR" 4
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.IX Item "info [-f fmt] filename"
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Give information about the disk image \fIfilename\fR. Use it in
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particular to know the size reserved on disk which can be different
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from the displayed size. If \s-1VM\s0 snapshots are stored in the disk image,
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they are displayed too.
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.IP "\fBsnapshot [\-l | \-a\fR \fIsnapshot\fR \fB| \-c\fR \fIsnapshot\fR \fB| \-d\fR \fIsnapshot\fR \fB]\fR \fIfilename\fR" 4
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.IX Item "snapshot [-l | -a snapshot | -c snapshot | -d snapshot ] filename"
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List, apply, create or delete snapshots in image \fIfilename\fR.
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.IP "\fBrebase [\-f\fR \fIfmt\fR\fB] [\-p] [\-u] \-b\fR \fIbacking_file\fR \fB[\-F\fR \fIbacking_fmt\fR\fB]\fR \fIfilename\fR" 4
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.IX Item "rebase [-f fmt] [-p] [-u] -b backing_file [-F backing_fmt] filename"
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Changes the backing file of an image. Only the formats \f(CW\*(C`qcow2\*(C'\fR and
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\&\f(CW\*(C`qed\*(C'\fR support changing the backing file.
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The backing file is changed to \fIbacking_file\fR and (if the image format of
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\&\fIfilename\fR supports this) the backing file format is changed to
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There are two different modes in which \f(CW\*(C`rebase\*(C'\fR can operate:
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.IP "\fBSafe mode\fR" 4
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This is the default mode and performs a real rebase operation. The new backing
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file may differ from the old one and qemu-img rebase will take care of keeping
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the guest-visible content of \fIfilename\fR unchanged.
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In order to achieve this, any clusters that differ between \fIbacking_file\fR
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and the old backing file of \fIfilename\fR are merged into \fIfilename\fR
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before actually changing the backing file.
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Note that the safe mode is an expensive operation, comparable to converting
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an image. It only works if the old backing file still exists.
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.IP "\fBUnsafe mode\fR" 4
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.IX Item "Unsafe mode"
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qemu-img uses the unsafe mode if \f(CW\*(C`\-u\*(C'\fR is specified. In this mode, only the
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backing file name and format of \fIfilename\fR is changed without any checks
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on the file contents. The user must take care of specifying the correct new
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backing file, or the guest-visible content of the image will be corrupted.
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This mode is useful for renaming or moving the backing file to somewhere else.
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It can be used without an accessible old backing file, i.e. you can use it to
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fix an image whose backing file has already been moved/renamed.
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.IP "\fBresize\fR \fIfilename\fR \fB[+ | \-]\fR\fIsize\fR" 4
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.IX Item "resize filename [+ | -]size"
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Change the disk image as if it had been created with \fIsize\fR.
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Before using this command to shrink a disk image, you \s-1MUST\s0 use file system and
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partitioning tools inside the \s-1VM\s0 to reduce allocated file systems and partition
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sizes accordingly. Failure to do so will result in data loss!
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After using this command to grow a disk image, you must use file system and
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partitioning tools inside the \s-1VM\s0 to actually begin using the new space on the
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Supported image file formats:
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Raw disk image format (default). This format has the advantage of
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being simple and easily exportable to all other emulators. If your
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file system supports \fIholes\fR (for example in ext2 or ext3 on
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Linux or \s-1NTFS\s0 on Windows), then only the written sectors will reserve
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space. Use \f(CW\*(C`qemu\-img info\*(C'\fR to know the real size used by the
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image or \f(CW\*(C`ls \-ls\*(C'\fR on Unix/Linux.
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\&\s-1QEMU\s0 image format, the most versatile format. Use it to have smaller
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images (useful if your filesystem does not supports holes, for example
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on Windows), optional \s-1AES\s0 encryption, zlib based compression and
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support of multiple \s-1VM\s0 snapshots.
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.ie n .IP """backing_file""" 4
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.el .IP "\f(CWbacking_file\fR" 4
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.IX Item "backing_file"
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File name of a base image (see \fBcreate\fR subcommand)
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.ie n .IP """backing_fmt""" 4
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.el .IP "\f(CWbacking_fmt\fR" 4
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.IX Item "backing_fmt"
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Image format of the base image
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.ie n .IP """encryption""" 4
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.el .IP "\f(CWencryption\fR" 4
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.IX Item "encryption"
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If this option is set to \f(CW\*(C`on\*(C'\fR, the image is encrypted.
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Encryption uses the \s-1AES\s0 format which is very secure (128 bit keys). Use
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a long password (16 characters) to get maximum protection.
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.ie n .IP """cluster_size""" 4
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.el .IP "\f(CWcluster_size\fR" 4
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.IX Item "cluster_size"
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Changes the qcow2 cluster size (must be between 512 and 2M). Smaller cluster
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sizes can improve the image file size whereas larger cluster sizes generally
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provide better performance.
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.ie n .IP """preallocation""" 4
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.el .IP "\f(CWpreallocation\fR" 4
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.IX Item "preallocation"
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Preallocation mode (allowed values: off, metadata). An image with preallocated
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metadata is initially larger but can improve performance when the image needs
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Old \s-1QEMU\s0 image format. Left for compatibility.
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.ie n .IP """backing_file""" 4
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.el .IP "\f(CWbacking_file\fR" 4
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.IX Item "backing_file"
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File name of a base image (see \fBcreate\fR subcommand)
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.ie n .IP """encryption""" 4
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.el .IP "\f(CWencryption\fR" 4
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.IX Item "encryption"
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If this option is set to \f(CW\*(C`on\*(C'\fR, the image is encrypted.
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User Mode Linux Copy On Write image format. Used to be the only growable
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image format in \s-1QEMU\s0. It is supported only for compatibility with
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previous versions. It does not work on win32.
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VirtualBox 1.1 compatible image format.
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VMware 3 and 4 compatible image format.
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.ie n .IP """backing_fmt""" 4
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.el .IP "\f(CWbacking_fmt\fR" 4
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.IX Item "backing_fmt"
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Image format of the base image
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.ie n .IP """compat6""" 4
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.el .IP "\f(CWcompat6\fR" 4
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Create a \s-1VMDK\s0 version 6 image (instead of version 4)
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VirtualPC compatible image format (\s-1VHD\s0).
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Linux Compressed Loop image, useful only to reuse directly compressed
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CD-ROM images present for example in the Knoppix CD-ROMs.
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.IX Header "SEE ALSO"
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The \s-1HTML\s0 documentation of \s-1QEMU\s0 for more precise information and Linux
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user mode emulator invocation.
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qemu-img.1
