


QEMU-IMG(1)                                           QEMU-IMG(1)


NAME
       qemu-img - QEMU disk image utility

SYNOPSIS
       usage: qemu-img command [command options]

OPTIONS
       The following commands are supported:

       check [-f fmt] filename
       create [-f fmt] [-o options] filename [size]
       commit [-f fmt] filename
       convert [-c] [-f fmt] [-O output_fmt] [-o options] filename [filename2
       [...]] output_filename
       info [-f fmt] filename
       snapshot [-l | -a snapshot | -c snapshot | -d snapshot] filename
       rebase [-f fmt] [-u] -b backing_file [-F backing_fmt] filename
       resize filename [+ | -]size

       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.

       -c  indicates that target image must be compressed (qcow format only)

       -h  with or without a command shows help and lists the supported
           formats

       Parameters to snapshot subcommand:

       snapshot
           is the name of the snapshot to create, apply or delete




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QEMU-IMG(1)                                           QEMU-IMG(1)


       -a  applies a snapshot (revert disk to saved state)

       -c  creates a snapshot

       -d  deletes a snapshot

       -l  lists all snapshots in the given image

       Command description:

       create [-f fmt] [-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).

           The size can also be specified using the size option with "-o", it
           doesn't need to be specified separately in this case.

       commit [-f fmt] filename
           Commit the changes recorded in filename in its base image.

       convert [-c] [-f fmt] [-O output_fmt] [-o options] filename [filename2
       [...]] output_filename
           Convert the disk image filename 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" or "cow": the empty sectors are
           detected and suppressed from the destination image.

           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.

       info [-f fmt] 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.

       snapshot [-l | -a snapshot | -c snapshot | -d snapshot ] filename
           List, apply, create or delete snapshots in image filename.




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QEMU-IMG(1)                                           QEMU-IMG(1)


       resize 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!

           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.

       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.

       host_device
           Host device format. This format should be used instead of raw when
           converting to block devices or other devices where "holes" are not
           supported.

       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:

           "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.

               Encryption uses the AES format which is very secure (128 bit
               keys). Use a long password (16 characters) to get maximum
               protection.

           "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). An image



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QEMU-IMG(1)                                           QEMU-IMG(1)


               with preallocated metadata is initially larger but can improve
               performance when the image needs to grow.

       qcow
           Old QEMU image format. Left for compatibility.

           Supported options:

           "backing_file"
               File name of a base image (see create subcommand)

           "encryption"
               If this option is set to "on", the image is encrypted.

       cow User Mode Linux Copy On Write image format. Used to be the only
           growable image format in QEMU. It is supported only for
           compatibility with previous versions. It does not work on win32.

       vdi VirtualBox 1.1 compatible image format.

       vmdk
           VMware 3 and 4 compatible image format.

           Supported options:

           "backing_fmt"
               Image format of the base image

           "compat6"
               Create a VMDK version 6 image (instead of version 4)

       vpc VirtualPC compatible image format (VHD).

       cloop
           Linux Compressed Loop image, useful only to reuse directly
           compressed CD-ROM images present for example in the Knoppix CD-
           ROMs.

SEE ALSO
       The HTML documentation of QEMU for more precise information and Linux
       user mode emulator invocation.

AUTHOR
       Fabrice Bellard













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