diff options
| author | Andrey Drobyshev <andrey.drobyshev@virtuozzo.com> | 2023-09-19 19:58:03 +0300 |
|---|---|---|
| committer | Kevin Wolf <kwolf@redhat.com> | 2023-10-31 13:51:28 +0100 |
| commit | 26ea27898b2b4e322ab932fb61de8f32cd9e4d72 (patch) | |
| tree | 02e218372161f4e07a441dabf68826878f64d56e /docs/tools | |
| parent | f93e65ee5175a8f8449913553100747aaafecc4d (diff) | |
qemu-img: add compression option to rebase subcommand
If we rebase an image whose backing file has compressed clusters, we
might end up wasting disk space since the copied clusters are now
uncompressed. In order to have better control over this, let's add
"--compress" option to the "qemu-img rebase" command.
Note that this option affects only the clusters which are actually being
copied from the original backing file. The clusters which were
uncompressed in the target image will remain so.
Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
Reviewed-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
Message-ID: <20230919165804.439110-8-andrey.drobyshev@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'docs/tools')
| -rw-r--r-- | docs/tools/qemu-img.rst | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/docs/tools/qemu-img.rst b/docs/tools/qemu-img.rst index ca5a2773cf..4459c065f1 100644 --- a/docs/tools/qemu-img.rst +++ b/docs/tools/qemu-img.rst @@ -667,7 +667,7 @@ Command description: List, apply, create or delete snapshots in image *FILENAME*. -.. option:: rebase [--object OBJECTDEF] [--image-opts] [-U] [-q] [-f FMT] [-t CACHE] [-T SRC_CACHE] [-p] [-u] -b BACKING_FILE [-F BACKING_FMT] FILENAME +.. option:: rebase [--object OBJECTDEF] [--image-opts] [-U] [-q] [-f FMT] [-t CACHE] [-T SRC_CACHE] [-p] [-u] [-c] -b BACKING_FILE [-F BACKING_FMT] FILENAME Changes the backing file of an image. Only the formats ``qcow2`` and ``qed`` support changing the backing file. @@ -694,7 +694,9 @@ Command description: In order to achieve this, any clusters that differ between *BACKING_FILE* and the old backing file of *FILENAME* are merged - into *FILENAME* before actually changing the backing file. + into *FILENAME* before actually changing the backing file. With the + ``-c`` option specified, the clusters which are being merged (but not + the entire *FILENAME* image) are compressed when written. Note that the safe mode is an expensive operation, comparable to converting an image. It only works if the old backing file still |