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 @item -p
  42 display progress bar (convert and rebase commands only)
  43 @item -S @var{size}
  44 indicates the consecutive number of bytes that must contain only zeros
  45 for qemu-img to create a sparse image during conversion. This value is rounded
  46 down to the nearest 512 bytes. You may use the common size suffixes like
  47 @code{k} for kilobytes.
  48 @item -t @var{cache}
  49 specifies the cache mode that should be used with the (destination) file. See
  50 the documentation of the emulator's @code{-drive cache=...} option for allowed
  51 values.
  52 @end table
  53
  54 Parameters to snapshot subcommand:
  55
  56 @table @option
  57
  58 @item snapshot
  59 is the name of the snapshot to create, apply or delete
  60 @item -a
  61 applies a snapshot (revert disk to saved state)
  62 @item -c
  63 creates a snapshot
  64 @item -d
  65 deletes a snapshot
  66 @item -l
  67 lists all snapshots in the given image
  68 @end table
  69
  70 Command description:
  71
  72 @table @option
  73 @item check [-f @var{fmt}] @var{filename}
  74
  75 Perform a consistency check on the disk image @var{filename}.
  76
  77 Only the formats @code{qcow2}, @code{qed} and @code{vdi} support
  78 consistency checks.
  79
  80 @item create [-f @var{fmt}] [-o @var{options}] @var{filename} [@var{size}]
  81
  82 Create the new disk image @var{filename} of size @var{size} and format
  83 @var{fmt}. Depending on the file format, you can add one or more @var{options}
  84 that enable additional features of this format.
  85
  86 If the option @var{backing_file} is specified, then the image will record
  87 only the differences from @var{backing_file}. No size needs to be specified in
  88 this case. @var{backing_file} will never be modified unless you use the
  89 @code{commit} monitor command (or qemu-img commit).
  90
  91 The size can also be specified using the @var{size} option with @code{-o},
  92 it doesn't need to be specified separately in this case.
  93
  94 @item commit [-f @var{fmt}] [-t @var{cache}] @var{filename}
  95
  96 Commit the changes recorded in @var{filename} in its base image.
  97
  98 @item convert [-c] [-p] [-f @var{fmt}] [-t @var{cache}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_name}] [-S @var{sparse_size}] @var{filename} [@var{filename2} [...]] @var{output_filename}
  99
 100 Convert the disk image @var{filename} or a snapshot @var{snapshot_name} to disk image @var{output_filename}
 101 using format @var{output_fmt}. It can be optionally compressed (@code{-c}
 102 option) or use any format specific options like encryption (@code{-o} option).
 103
 104 Only the formats @code{qcow} and @code{qcow2} support compression. The
 105 compression is read-only. It means that if a compressed sector is
 106 rewritten, then it is rewritten as uncompressed data.
 107
 108 Image conversion is also useful to get smaller image when using a
 109 growable format such as @code{qcow} or @code{cow}: the empty sectors
 110 are detected and suppressed from the destination image.
 111
 112 You can use the @var{backing_file} option to force the output image to be
 113 created as a copy on write image of the specified base image; the
 114 @var{backing_file} should have the same content as the input's base image,
 115 however the path, image format, etc may differ.
 116
 117 @item info [-f @var{fmt}] @var{filename}
 118
 119 Give information about the disk image @var{filename}. Use it in
 120 particular to know the size reserved on disk which can be different
 121 from the displayed size. If VM snapshots are stored in the disk image,
 122 they are displayed too.
 123
 124 @item snapshot [-l | -a @var{snapshot} | -c @var{snapshot} | -d @var{snapshot} ] @var{filename}
 125
 126 List, apply, create or delete snapshots in image @var{filename}.
 127
 128 @item rebase [-f @var{fmt}] [-t @var{cache}] [-p] [-u] -b @var{backing_file} [-F @var{backing_fmt}] @var{filename}
 129
 130 Changes the backing file of an image. Only the formats @code{qcow2} and
 131 @code{qed} support changing the backing file.
 132
 133 The backing file is changed to @var{backing_file} and (if the image format of
 134 @var{filename} supports this) the backing file format is changed to
 135 @var{backing_fmt}.
 136
 137 There are two different modes in which @code{rebase} can operate:
 138 @table @option
 139 @item Safe mode
 140 This is the default mode and performs a real rebase operation. The new backing
 141 file may differ from the old one and qemu-img rebase will take care of keeping
 142 the guest-visible content of @var{filename} unchanged.
 143
 144 In order to achieve this, any clusters that differ between @var{backing_file}
 145 and the old backing file of @var{filename} are merged into @var{filename}
 146 before actually changing the backing file.
 147
 148 Note that the safe mode is an expensive operation, comparable to converting
 149 an image. It only works if the old backing file still exists.
 150
 151 @item Unsafe mode
 152 qemu-img uses the unsafe mode if @code{-u} is specified. In this mode, only the
 153 backing file name and format of @var{filename} is changed without any checks
 154 on the file contents. The user must take care of specifying the correct new
 155 backing file, or the guest-visible content of the image will be corrupted.
 156
 157 This mode is useful for renaming or moving the backing file to somewhere else.
 158 It can be used without an accessible old backing file, i.e. you can use it to
 159 fix an image whose backing file has already been moved/renamed.
 160 @end table
 161
 162 @item resize @var{filename} [+ | -]@var{size}
 163
 164 Change the disk image as if it had been created with @var{size}.
 165
 166 Before using this command to shrink a disk image, you MUST use file system and
 167 partitioning tools inside the VM to reduce allocated file systems and partition
 168 sizes accordingly.  Failure to do so will result in data loss!
 169
 170 After using this command to grow a disk image, you must use file system and
 171 partitioning tools inside the VM to actually begin using the new space on the
 172 device.
 173 @end table
 174
 175 Supported image file formats:
 176
 177 @table @option
 178 @item raw
 179
 180 Raw disk image format (default). This format has the advantage of
 181 being simple and easily exportable to all other emulators. If your
 182 file system supports @emph{holes} (for example in ext2 or ext3 on
 183 Linux or NTFS on Windows), then only the written sectors will reserve
 184 space. Use @code{qemu-img info} to know the real size used by the
 185 image or @code{ls -ls} on Unix/Linux.
 186
 187 @item qcow2
 188 QEMU image format, the most versatile format. Use it to have smaller
 189 images (useful if your filesystem does not supports holes, for example
 190 on Windows), optional AES encryption, zlib based compression and
 191 support of multiple VM snapshots.
 192
 193 Supported options:
 194 @table @code
 195 @item backing_file
 196 File name of a base image (see @option{create} subcommand)
 197 @item backing_fmt
 198 Image format of the base image
 199 @item encryption
 200 If this option is set to @code{on}, the image is encrypted.
 201
 202 Encryption uses the AES format which is very secure (128 bit keys). Use
 203 a long password (16 characters) to get maximum protection.
 204
 205 @item cluster_size
 206 Changes the qcow2 cluster size (must be between 512 and 2M). Smaller cluster
 207 sizes can improve the image file size whereas larger cluster sizes generally
 208 provide better performance.
 209
 210 @item preallocation
 211 Preallocation mode (allowed values: off, metadata). An image with preallocated
 212 metadata is initially larger but can improve performance when the image needs
 213 to grow.
 214
 215 @end table
 216
 217
 218 @item qcow
 219 Old QEMU image format. Left for compatibility.
 220
 221 Supported options:
 222 @table @code
 223 @item backing_file
 224 File name of a base image (see @option{create} subcommand)
 225 @item encryption
 226 If this option is set to @code{on}, the image is encrypted.
 227 @end table
 228
 229 @item cow
 230 User Mode Linux Copy On Write image format. Used to be the only growable
 231 image format in QEMU. It is supported only for compatibility with
 232 previous versions. It does not work on win32.
 233 @item vdi
 234 VirtualBox 1.1 compatible image format.
 235 @item vmdk
 236 VMware 3 and 4 compatible image format.
 237
 238 Supported options:
 239 @table @code
 240 @item backing_fmt
 241 Image format of the base image
 242 @item compat6
 243 Create a VMDK version 6 image (instead of version 4)
 244 @end table
 245
 246 @item vpc
 247 VirtualPC compatible image format (VHD).
 248
 249 @item cloop
 250 Linux Compressed Loop image, useful only to reuse directly compressed
 251 CD-ROM images present for example in the Knoppix CD-ROMs.
 252 @end table
 253
 254
 255 @c man end
 256
 257 @ignore
 258
 259 @setfilename qemu-img
 260 @settitle QEMU disk image utility
 261
 262 @c man begin SEEALSO
 263 The HTML documentation of QEMU for more precise information and Linux
 264 user mode emulator invocation.
 265 @c man end
 266
 267 @c man begin AUTHOR
 268 Fabrice Bellard
 269 @c man end
 270
 271 @end ignore