diff options
Diffstat (limited to 'qemu-img.texi')
| -rw-r--r-- | qemu-img.texi | 38 |
1 files changed, 17 insertions, 21 deletions
diff --git a/qemu-img.texi b/qemu-img.texi index dd248eadc5..2d0106b84d 100644 --- a/qemu-img.texi +++ b/qemu-img.texi @@ -14,16 +14,6 @@ Command parameters: @table @var @item filename is a disk image filename -@item base_image -is the read-only disk image which is used as base for a copy on - write image; the copy on write image only stores the modified data -@item output_base_image -forces the output image to be created as a copy on write -image of the specified base image; @code{output_base_image} should have the same -content as the input's base image, however the path, image format, etc may -differ -@item base_fmt -is the disk image format of @var{base_image}. for more information look at @var{fmt} @item fmt is the disk image format. It is guessed automatically in most cases. See below for a description of the supported disk formats. @@ -69,15 +59,16 @@ lists all snapshots in the given image Command description: @table @option -@item create [-F @var{base_fmt}] [-b @var{base_image}] [-f @var{fmt}] [-o @var{options}] @var{filename} [@var{size}] +@item create [-f @var{fmt}] [-o @var{options}] @var{filename} [@var{size}] Create the new disk image @var{filename} of size @var{size} and format -@var{fmt}. +@var{fmt}. Depending on the file format, you can add one or more @var{options} +that enable additional features of this format. -If @var{base_image} is specified, then the image will record only the -differences from @var{base_image}. No size needs to be specified in -this case. @var{base_image} will never be modified unless you use the -@code{commit} monitor command. +If the option @var{backing_file} is specified, then the image will record +only the differences from @var{backing_file}. No size needs to be specified in +this case. @var{backing_file} will never be modified unless you use the +@code{commit} monitor command (or qemu-img commit). The size can also be specified using the @var{size} option with @code{-o}, it doesn't need to be specified separately in this case. @@ -86,23 +77,25 @@ it doesn't need to be specified separately in this case. Commit the changes recorded in @var{filename} in its base image. -@item convert [-c] [-f @var{fmt}] [-O @var{output_fmt}] [-o @var{options}] [-B @var{output_base_image}] @var{filename} [@var{filename2} [...]] @var{output_filename} +@item convert [-c] [-f @var{fmt}] [-O @var{output_fmt}] [-o @var{options}] @var{filename} [@var{filename2} [...]] @var{output_filename} Convert the disk image @var{filename} to disk image @var{output_filename} using format @var{output_fmt}. It can be optionally compressed (@code{-c} option) or use any format specific options like encryption (@code{-o} option). -Only the formats @code{qcow} and @code{qcow2} support encryption or compression. The +Only the formats @code{qcow} and @code{qcow2} support compression. The compression is read-only. It means that if a compressed sector is rewritten, then it is rewritten as uncompressed data. -Encryption uses the AES format which is very secure (128 bit keys). Use -a long password (16 characters) to get maximum protection. - Image conversion is also useful to get smaller image when using a growable format such as @code{qcow} or @code{cow}: the empty sectors are detected and suppressed from the destination image. +You can use the @var{backing_file} option to force the output image to be +created as a copy on write image of the specified base image; the +@var{backing_file} should have the same content as the input's base image, +however the path, image format, etc may differ. + @item info [-f @var{fmt}] @var{filename} Give information about the disk image @var{filename}. Use it in @@ -138,6 +131,9 @@ 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. + +Encryption uses the AES format which is very secure (128 bit keys). Use +a long password (16 characters) to get maximum protection. @item qcow Old QEMU image format. Left for compatibility. @item cow |