Commit e6184690 authored by Kevin Wolf's avatar Kevin Wolf
Browse files

Documentation: Add qemu-img check/rebase

Signed-off-by: default avatarKevin Wolf <>
parent 1635eecc
......@@ -59,6 +59,13 @@ lists all snapshots in the given image
Command description:
@table @option
@item check [-f @var{fmt}] @var{filename}
Perform a consistency check on the disk image @var{filename}.
Only the formats @code{qcow2}, @code{qed} and @code{vdi} support
consistency checks.
@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
......@@ -107,6 +114,40 @@ they are displayed too.
List, apply, create or delete snapshots in image @var{filename}.
@item rebase [-f @var{fmt}] [-u] -b @var{backing_file} [-F @var{backing_fmt}] @var{filename}
Changes the backing file of an image. Only the formats @code{qcow2} and
@code{qed} support changing the backing file.
The backing file is changed to @var{backing_file} and (if the image format of
@var{filename} supports this) the backing file format is changed to
There are two different modes in which @code{rebase} can operate:
@table @option
@item Safe mode
This is the default mode and performs a real rebase operation. The new backing
file may differ from the old one and qemu-img rebase will take care of keeping
the guest-visible content of @var{filename} unchanged.
In order to achieve this, any clusters that differ between @var{backing_file}
and the old backing file of @var{filename} are merged into @var{filename}
before actually changing the backing file.
Note that the safe mode is an expensive operation, comparable to converting
an image. It only works if the old backing file still exists.
@item Unsafe mode
qemu-img uses the unsafe mode if @code{-u} is specified. In this mode, only the
backing file name and format of @var{filename} is changed without any checks
on the file contents. The user must take care of specifying the correct new
backing file, or the guest-visible content of the image will be corrupted.
This mode is useful for renaming or moving the backing file to somewhere else.
It can be used without an accessible old backing file, i.e. you can use it to
fix an image whose backing file has already been moved/renamed.
@end table
@item resize @var{filename} [+ | -]@var{size}
Change the disk image as if it had been created with @var{size}.
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