qemu-img.texi

   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 @end table
  42
  43 Parameters to snapshot subcommand:
  44
  45 @table @option
  46
  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
  58
  59 Command description:
  60
  61 @table @option
  62 @item check [-f @var{fmt}] @var{filename}
  63
  64 Perform a consistency check on the disk image @var{filename}.
  65
  66 Only the formats @code{qcow2}, @code{qed} and @code{vdi} support
  67 consistency checks.
  68
  69 @item create [-f @var{fmt}] [-o @var{options}] @var{filename} [@var{size}]
  70
  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.
  74
  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).
  79
  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.
  82
  83 @item commit [-f @var{fmt}] @var{filename}
  84
  85 Commit the changes recorded in @var{filename} in its base image.
  86
  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}
  88
  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).
  92
  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.
  96
  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.
 100
 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.
 105
 106 @item info [-f @var{fmt}] @var{filename}
 107
 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.
 112
 113 @item snapshot [-l | -a @var{snapshot} | -c @var{snapshot} | -d @var{snapshot} ] @var{filename}
 114
 115 List, apply, create or delete snapshots in image @var{filename}.
 116
 117 @item rebase [-f @var{fmt}] [-u] -b @var{backing_file} [-F @var{backing_fmt}] @var{filename}
 118
 119 Changes the backing file of an image. Only the formats @code{qcow2} and
 120 @code{qed} support changing the backing file.
 121
 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}.
 125
 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.
 132
 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.
 136
 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.
 139
 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.
 145
 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
 150
 151 @item resize @var{filename} [+ | -]@var{size}
 152
 153 Change the disk image as if it had been created with @var{size}.
 154
 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!
 158
 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
 163
 164 Supported image file formats:
 165
 166 @table @option
 167 @item raw
 168
 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.
 175
 176 @item host_device
 177
 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.
 181
 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.
 187
 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.
 196
 197 Encryption uses the AES format which is very secure (128 bit keys). Use
 198 a long password (16 characters) to get maximum protection.
 199
 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.
 204
 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.
 209
 210 @end table
 211
 212
 213 @item qcow
 214 Old QEMU image format. Left for compatibility.
 215
 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
 223
 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.
 232
 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
 240
 241 @item vpc
 242 VirtualPC compatible image format (VHD).
 243
 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
 248
 249
 250 @c man end
 251
 252 @ignore
 253
 254 @setfilename qemu-img
 255 @settitle QEMU disk image utility
 256
 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
 261
 262 @c man begin AUTHOR
 263 Fabrice Bellard
 264 @c man end
 265
 266 @end ignore