File:  [Qemu by Fabrice Bellard] / qemu / qemu-img.texi
Revision 1.1.1.9 (vendor branch): download - view: text, annotated - select for diffs
Tue Apr 24 18:56:48 2018 UTC (3 years, 1 month ago) by root
Branches: qemu, MAIN
CVS tags: qemu1000, qemu0151, HEAD
qemu 0.15.1

    1: @example
    2: @c man begin SYNOPSIS
    3: usage: qemu-img command [command options]
    4: @c man end
    5: @end example
    6: 
    7: @c man begin OPTIONS
    8: 
    9: The following commands are supported:
   10: 
   11: @include qemu-img-cmds.texi
   12: 
   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.
   20: 
   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.
   25: 
   26: @item output_filename
   27: is the destination disk image filename
   28: 
   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.
   35: 
   36: 
   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: @item -p
   42: display progress bar (convert and rebase commands only)
   43: @end table
   44: 
   45: Parameters to snapshot subcommand:
   46: 
   47: @table @option
   48: 
   49: @item snapshot
   50: is the name of the snapshot to create, apply or delete
   51: @item -a
   52: applies a snapshot (revert disk to saved state)
   53: @item -c
   54: creates a snapshot
   55: @item -d
   56: deletes a snapshot
   57: @item -l
   58: lists all snapshots in the given image
   59: @end table
   60: 
   61: Command description:
   62: 
   63: @table @option
   64: @item check [-f @var{fmt}] @var{filename}
   65: 
   66: Perform a consistency check on the disk image @var{filename}.
   67: 
   68: Only the formats @code{qcow2}, @code{qed} and @code{vdi} support
   69: consistency checks.
   70: 
   71: @item create [-f @var{fmt}] [-o @var{options}] @var{filename} [@var{size}]
   72: 
   73: Create the new disk image @var{filename} of size @var{size} and format
   74: @var{fmt}. Depending on the file format, you can add one or more @var{options}
   75: that enable additional features of this format.
   76: 
   77: If the option @var{backing_file} is specified, then the image will record
   78: only the differences from @var{backing_file}. No size needs to be specified in
   79: this case. @var{backing_file} will never be modified unless you use the
   80: @code{commit} monitor command (or qemu-img commit).
   81: 
   82: The size can also be specified using the @var{size} option with @code{-o},
   83: it doesn't need to be specified separately in this case.
   84: 
   85: @item commit [-f @var{fmt}] @var{filename}
   86: 
   87: Commit the changes recorded in @var{filename} in its base image.
   88: 
   89: @item convert [-c] [-p] [-f @var{fmt}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_name}] @var{filename} [@var{filename2} [...]] @var{output_filename}
   90: 
   91: Convert the disk image @var{filename} or a snapshot @var{snapshot_name} to disk image @var{output_filename}
   92: using format @var{output_fmt}. It can be optionally compressed (@code{-c}
   93: option) or use any format specific options like encryption (@code{-o} option).
   94: 
   95: Only the formats @code{qcow} and @code{qcow2} support compression. The
   96: compression is read-only. It means that if a compressed sector is
   97: rewritten, then it is rewritten as uncompressed data.
   98: 
   99: Image conversion is also useful to get smaller image when using a
  100: growable format such as @code{qcow} or @code{cow}: the empty sectors
  101: are detected and suppressed from the destination image.
  102: 
  103: You can use the @var{backing_file} option to force the output image to be
  104: created as a copy on write image of the specified base image; the
  105: @var{backing_file} should have the same content as the input's base image,
  106: however the path, image format, etc may differ.
  107: 
  108: @item info [-f @var{fmt}] @var{filename}
  109: 
  110: Give information about the disk image @var{filename}. Use it in
  111: particular to know the size reserved on disk which can be different
  112: from the displayed size. If VM snapshots are stored in the disk image,
  113: they are displayed too.
  114: 
  115: @item snapshot [-l | -a @var{snapshot} | -c @var{snapshot} | -d @var{snapshot} ] @var{filename}
  116: 
  117: List, apply, create or delete snapshots in image @var{filename}.
  118: 
  119: @item rebase [-f @var{fmt}] [-p] [-u] -b @var{backing_file} [-F @var{backing_fmt}] @var{filename}
  120: 
  121: Changes the backing file of an image. Only the formats @code{qcow2} and
  122: @code{qed} support changing the backing file.
  123: 
  124: The backing file is changed to @var{backing_file} and (if the image format of
  125: @var{filename} supports this) the backing file format is changed to
  126: @var{backing_fmt}.
  127: 
  128: There are two different modes in which @code{rebase} can operate:
  129: @table @option
  130: @item Safe mode
  131: This is the default mode and performs a real rebase operation. The new backing
  132: file may differ from the old one and qemu-img rebase will take care of keeping
  133: the guest-visible content of @var{filename} unchanged.
  134: 
  135: In order to achieve this, any clusters that differ between @var{backing_file}
  136: and the old backing file of @var{filename} are merged into @var{filename}
  137: before actually changing the backing file.
  138: 
  139: Note that the safe mode is an expensive operation, comparable to converting
  140: an image. It only works if the old backing file still exists.
  141: 
  142: @item Unsafe mode
  143: qemu-img uses the unsafe mode if @code{-u} is specified. In this mode, only the
  144: backing file name and format of @var{filename} is changed without any checks
  145: on the file contents. The user must take care of specifying the correct new
  146: backing file, or the guest-visible content of the image will be corrupted.
  147: 
  148: This mode is useful for renaming or moving the backing file to somewhere else.
  149: It can be used without an accessible old backing file, i.e. you can use it to
  150: fix an image whose backing file has already been moved/renamed.
  151: @end table
  152: 
  153: @item resize @var{filename} [+ | -]@var{size}
  154: 
  155: Change the disk image as if it had been created with @var{size}.
  156: 
  157: Before using this command to shrink a disk image, you MUST use file system and
  158: partitioning tools inside the VM to reduce allocated file systems and partition
  159: sizes accordingly.  Failure to do so will result in data loss!
  160: 
  161: After using this command to grow a disk image, you must use file system and
  162: partitioning tools inside the VM to actually begin using the new space on the
  163: device.
  164: @end table
  165: 
  166: Supported image file formats:
  167: 
  168: @table @option
  169: @item raw
  170: 
  171: Raw disk image format (default). This format has the advantage of
  172: being simple and easily exportable to all other emulators. If your
  173: file system supports @emph{holes} (for example in ext2 or ext3 on
  174: Linux or NTFS on Windows), then only the written sectors will reserve
  175: space. Use @code{qemu-img info} to know the real size used by the
  176: image or @code{ls -ls} on Unix/Linux.
  177: 
  178: @item qcow2
  179: QEMU image format, the most versatile format. Use it to have smaller
  180: images (useful if your filesystem does not supports holes, for example
  181: on Windows), optional AES encryption, zlib based compression and
  182: support of multiple VM snapshots.
  183: 
  184: Supported options:
  185: @table @code
  186: @item backing_file
  187: File name of a base image (see @option{create} subcommand)
  188: @item backing_fmt
  189: Image format of the base image
  190: @item encryption
  191: If this option is set to @code{on}, the image is encrypted.
  192: 
  193: Encryption uses the AES format which is very secure (128 bit keys). Use
  194: a long password (16 characters) to get maximum protection.
  195: 
  196: @item cluster_size
  197: Changes the qcow2 cluster size (must be between 512 and 2M). Smaller cluster
  198: sizes can improve the image file size whereas larger cluster sizes generally
  199: provide better performance.
  200: 
  201: @item preallocation
  202: Preallocation mode (allowed values: off, metadata). An image with preallocated
  203: metadata is initially larger but can improve performance when the image needs
  204: to grow.
  205: 
  206: @end table
  207: 
  208: 
  209: @item qcow
  210: Old QEMU image format. Left for compatibility.
  211: 
  212: Supported options:
  213: @table @code
  214: @item backing_file
  215: File name of a base image (see @option{create} subcommand)
  216: @item encryption
  217: If this option is set to @code{on}, the image is encrypted.
  218: @end table
  219: 
  220: @item cow
  221: User Mode Linux Copy On Write image format. Used to be the only growable
  222: image format in QEMU. It is supported only for compatibility with
  223: previous versions. It does not work on win32.
  224: @item vdi
  225: VirtualBox 1.1 compatible image format.
  226: @item vmdk
  227: VMware 3 and 4 compatible image format.
  228: 
  229: Supported options:
  230: @table @code
  231: @item backing_fmt
  232: Image format of the base image
  233: @item compat6
  234: Create a VMDK version 6 image (instead of version 4)
  235: @end table
  236: 
  237: @item vpc
  238: VirtualPC compatible image format (VHD).
  239: 
  240: @item cloop
  241: Linux Compressed Loop image, useful only to reuse directly compressed
  242: CD-ROM images present for example in the Knoppix CD-ROMs.
  243: @end table
  244: 
  245: 
  246: @c man end
  247: 
  248: @ignore
  249: 
  250: @setfilename qemu-img
  251: @settitle QEMU disk image utility
  252: 
  253: @c man begin SEEALSO
  254: The HTML documentation of QEMU for more precise information and Linux
  255: user mode emulator invocation.
  256: @c man end
  257: 
  258: @c man begin AUTHOR
  259: Fabrice Bellard
  260: @c man end
  261: 
  262: @end ignore

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