Provided by: qemu-utils_1.0+noroms-0ubuntu13_amd64 bug


       qemu-img - QEMU disk image utility


       usage: qemu-img command [command options]


       The following commands are supported:

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

       Command parameters:

            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.

           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.

           is the destination disk image filename

            is the destination format

           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

       -p  display progress bar (convert and rebase commands only)

       -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.

       Parameters to snapshot subcommand:

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

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

       -c  creates a snapshot

       -d  deletes a snapshot

       -l  lists all snapshots in the given image

       Command description:

       check [-f fmt] filename
           Perform a consistency check on the disk image filename.

           Only the formats "qcow2", "qed" and "vdi" support consistency checks.

       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

           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] [-p] [-f fmt] [-O output_fmt] [-o options] [-s snapshot_name] [-S
       sparse_size] filename [filename2 [...]] output_filename
           Convert the disk image filename or a snapshot snapshot_name 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

           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.

       rebase [-f fmt] [-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.

           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.

       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.

           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:

               File name of a base image (see create subcommand)

               Image format of the base image

               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.

               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 mode (allowed values: off, metadata). An image with preallocated
               metadata is initially larger but can improve performance when the image needs to

           Old QEMU image format. Left for compatibility.

           Supported options:

               File name of a base image (see create subcommand)

               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.

           VMware 3 and 4 compatible image format.

           Supported options:

               Image format of the base image

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

       vpc VirtualPC compatible image format (VHD).

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


       The HTML documentation of QEMU for more precise information and Linux user mode emulator


       Fabrice Bellard

                                            2012-04-12                                QEMU-IMG(1)