File:  [Qemu by Fabrice Bellard] / qemu / qemu-img.texi
Revision (vendor branch): download - view: text, annotated - select for diffs
Tue Apr 24 18:34:32 2018 UTC (3 years, 1 month ago) by root
Branches: qemu, MAIN
CVS tags: qemu0150, qemu0141, qemu0140, HEAD
qemu 0.14.0

    1: @example
    2: @c man begin SYNOPSIS
    3: usage: qemu-img command [command options]
    4: @c man end
    5: @end example
    7: @c man begin OPTIONS
    9: The following commands are supported:
   11: @include qemu-img-cmds.texi
   13: Command parameters:
   14: @table @var
   15: @item filename
   16:  is a disk image filename
   17: @item fmt
   18: is the disk image format. It is guessed automatically in most cases. See below
   19: for a description of the supported disk formats.
   21: @item size
   22: is the disk image size in bytes. Optional suffixes @code{k} or @code{K}
   23: (kilobyte, 1024) @code{M} (megabyte, 1024k) and @code{G} (gigabyte, 1024M)
   24: and T (terabyte, 1024G) are supported.  @code{b} is ignored.
   26: @item output_filename
   27: is the destination disk image filename
   29: @item output_fmt
   30:  is the destination format
   31: @item options
   32: is a comma separated list of format specific options in a
   33: name=value format. Use @code{-o ?} for an overview of the options supported
   34: by the used format or see the format descriptions below for details.
   37: @item -c
   38: indicates that target image must be compressed (qcow format only)
   39: @item -h
   40: with or without a command shows help and lists the supported formats
   41: @end table
   43: Parameters to snapshot subcommand:
   45: @table @option
   47: @item snapshot
   48: is the name of the snapshot to create, apply or delete
   49: @item -a
   50: applies a snapshot (revert disk to saved state)
   51: @item -c
   52: creates a snapshot
   53: @item -d
   54: deletes a snapshot
   55: @item -l
   56: lists all snapshots in the given image
   57: @end table
   59: Command description:
   61: @table @option
   62: @item check [-f @var{fmt}] @var{filename}
   64: Perform a consistency check on the disk image @var{filename}.
   66: Only the formats @code{qcow2}, @code{qed} and @code{vdi} support
   67: consistency checks.
   69: @item create [-f @var{fmt}] [-o @var{options}] @var{filename} [@var{size}]
   71: Create the new disk image @var{filename} of size @var{size} and format
   72: @var{fmt}. Depending on the file format, you can add one or more @var{options}
   73: that enable additional features of this format.
   75: If the option @var{backing_file} is specified, then the image will record
   76: only the differences from @var{backing_file}. No size needs to be specified in
   77: this case. @var{backing_file} will never be modified unless you use the
   78: @code{commit} monitor command (or qemu-img commit).
   80: The size can also be specified using the @var{size} option with @code{-o},
   81: it doesn't need to be specified separately in this case.
   83: @item commit [-f @var{fmt}] @var{filename}
   85: Commit the changes recorded in @var{filename} in its base image.
   87: @item convert [-c] [-f @var{fmt}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_name}] @var{filename} [@var{filename2} [...]] @var{output_filename}
   89: Convert the disk image @var{filename} or a snapshot @var{snapshot_name} to disk image @var{output_filename}
   90: using format @var{output_fmt}. It can be optionally compressed (@code{-c}
   91: option) or use any format specific options like encryption (@code{-o} option).
   93: Only the formats @code{qcow} and @code{qcow2} support compression. The
   94: compression is read-only. It means that if a compressed sector is
   95: rewritten, then it is rewritten as uncompressed data.
   97: Image conversion is also useful to get smaller image when using a
   98: growable format such as @code{qcow} or @code{cow}: the empty sectors
   99: are detected and suppressed from the destination image.
  101: You can use the @var{backing_file} option to force the output image to be
  102: created as a copy on write image of the specified base image; the
  103: @var{backing_file} should have the same content as the input's base image,
  104: however the path, image format, etc may differ.
  106: @item info [-f @var{fmt}] @var{filename}
  108: Give information about the disk image @var{filename}. Use it in
  109: particular to know the size reserved on disk which can be different
  110: from the displayed size. If VM snapshots are stored in the disk image,
  111: they are displayed too.
  113: @item snapshot [-l | -a @var{snapshot} | -c @var{snapshot} | -d @var{snapshot} ] @var{filename}
  115: List, apply, create or delete snapshots in image @var{filename}.
  117: @item rebase [-f @var{fmt}] [-u] -b @var{backing_file} [-F @var{backing_fmt}] @var{filename}
  119: Changes the backing file of an image. Only the formats @code{qcow2} and
  120: @code{qed} support changing the backing file.
  122: The backing file is changed to @var{backing_file} and (if the image format of
  123: @var{filename} supports this) the backing file format is changed to
  124: @var{backing_fmt}.
  126: There are two different modes in which @code{rebase} can operate:
  127: @table @option
  128: @item Safe mode
  129: This is the default mode and performs a real rebase operation. The new backing
  130: file may differ from the old one and qemu-img rebase will take care of keeping
  131: the guest-visible content of @var{filename} unchanged.
  133: In order to achieve this, any clusters that differ between @var{backing_file}
  134: and the old backing file of @var{filename} are merged into @var{filename}
  135: before actually changing the backing file.
  137: Note that the safe mode is an expensive operation, comparable to converting
  138: an image. It only works if the old backing file still exists.
  140: @item Unsafe mode
  141: qemu-img uses the unsafe mode if @code{-u} is specified. In this mode, only the
  142: backing file name and format of @var{filename} is changed without any checks
  143: on the file contents. The user must take care of specifying the correct new
  144: backing file, or the guest-visible content of the image will be corrupted.
  146: This mode is useful for renaming or moving the backing file to somewhere else.
  147: It can be used without an accessible old backing file, i.e. you can use it to
  148: fix an image whose backing file has already been moved/renamed.
  149: @end table
  151: @item resize @var{filename} [+ | -]@var{size}
  153: Change the disk image as if it had been created with @var{size}.
  155: Before using this command to shrink a disk image, you MUST use file system and
  156: partitioning tools inside the VM to reduce allocated file systems and partition
  157: sizes accordingly.  Failure to do so will result in data loss!
  159: After using this command to grow a disk image, you must use file system and
  160: partitioning tools inside the VM to actually begin using the new space on the
  161: device.
  162: @end table
  164: Supported image file formats:
  166: @table @option
  167: @item raw
  169: Raw disk image format (default). This format has the advantage of
  170: being simple and easily exportable to all other emulators. If your
  171: file system supports @emph{holes} (for example in ext2 or ext3 on
  172: Linux or NTFS on Windows), then only the written sectors will reserve
  173: space. Use @code{qemu-img info} to know the real size used by the
  174: image or @code{ls -ls} on Unix/Linux.
  176: @item host_device
  178: Host device format. This format should be used instead of raw when
  179: converting to block devices or other devices where "holes" are not
  180: supported.
  182: @item qcow2
  183: QEMU image format, the most versatile format. Use it to have smaller
  184: images (useful if your filesystem does not supports holes, for example
  185: on Windows), optional AES encryption, zlib based compression and
  186: support of multiple VM snapshots.
  188: Supported options:
  189: @table @code
  190: @item backing_file
  191: File name of a base image (see @option{create} subcommand)
  192: @item backing_fmt
  193: Image format of the base image
  194: @item encryption
  195: If this option is set to @code{on}, the image is encrypted.
  197: Encryption uses the AES format which is very secure (128 bit keys). Use
  198: a long password (16 characters) to get maximum protection.
  200: @item cluster_size
  201: Changes the qcow2 cluster size (must be between 512 and 2M). Smaller cluster
  202: sizes can improve the image file size whereas larger cluster sizes generally
  203: provide better performance.
  205: @item preallocation
  206: Preallocation mode (allowed values: off, metadata). An image with preallocated
  207: metadata is initially larger but can improve performance when the image needs
  208: to grow.
  210: @end table
  213: @item qcow
  214: Old QEMU image format. Left for compatibility.
  216: Supported options:
  217: @table @code
  218: @item backing_file
  219: File name of a base image (see @option{create} subcommand)
  220: @item encryption
  221: If this option is set to @code{on}, the image is encrypted.
  222: @end table
  224: @item cow
  225: User Mode Linux Copy On Write image format. Used to be the only growable
  226: image format in QEMU. It is supported only for compatibility with
  227: previous versions. It does not work on win32.
  228: @item vdi
  229: VirtualBox 1.1 compatible image format.
  230: @item vmdk
  231: VMware 3 and 4 compatible image format.
  233: Supported options:
  234: @table @code
  235: @item backing_fmt
  236: Image format of the base image
  237: @item compat6
  238: Create a VMDK version 6 image (instead of version 4)
  239: @end table
  241: @item vpc
  242: VirtualPC compatible image format (VHD).
  244: @item cloop
  245: Linux Compressed Loop image, useful only to reuse directly compressed
  246: CD-ROM images present for example in the Knoppix CD-ROMs.
  247: @end table
  250: @c man end
  252: @ignore
  254: @setfilename qemu-img
  255: @settitle QEMU disk image utility
  257: @c man begin SEEALSO
  258: The HTML documentation of QEMU for more precise information and Linux
  259: user mode emulator invocation.
  260: @c man end
  262: @c man begin AUTHOR
  263: Fabrice Bellard
  264: @c man end
  266: @end ignore