path: root/qemu-img.texi
diff options
authorJeff Cody <jcody@redhat.com>2014-01-24 09:02:37 -0500
committerKevin Wolf <kwolf@redhat.com>2014-01-24 16:12:49 +0100
commit37222900743962e146a82b7077a18c3f39859a19 (patch)
treebb0f5579a3ed79acf046886598c941788f29c6bd /qemu-img.texi
parent4da83585961631bfc10831dd26c4afda2a8b23e8 (diff)
block: update block commit documentation regarding image truncation
This updates the documentation for commiting snapshot images. Specifically, this highlights what happens when the base image is either smaller or larger than the snapshot image being committed. In the case of the base image being smaller, it is resized to the larger size of the snapshot image. In the case of the base image being larger, it is not resized automatically, but once the commit has completed it is safe for the user to truncate the base image. Signed-off-by: Jeff Cody <jcody@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'qemu-img.texi')
1 files changed, 6 insertions, 1 deletions
diff --git a/qemu-img.texi b/qemu-img.texi
index f86a86d916..526d56a458 100644
--- a/qemu-img.texi
+++ b/qemu-img.texi
@@ -142,7 +142,12 @@ it doesn't need to be specified separately in this case.
@item commit [-f @var{fmt}] [-t @var{cache}] @var{filename}
-Commit the changes recorded in @var{filename} in its base image.
+Commit the changes recorded in @var{filename} in its base image or backing file.
+If the backing file is smaller than the snapshot, then the backing file will be
+resized to be the same size as the snapshot. If the snapshot is smaller than
+the backing file, the backing file will not be truncated. If you want the
+backing file to match the size of the smaller snapshot, you can safely truncate
+it yourself once the commit operation successfully completes.
@item compare [-f @var{fmt}] [-F @var{fmt}] [-p] [-s] [-q] @var{filename1} @var{filename2}