From 37222900743962e146a82b7077a18c3f39859a19 Mon Sep 17 00:00:00 2001 From: Jeff Cody Date: Fri, 24 Jan 2014 09:02:37 -0500 Subject: 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 Reviewed-by: Fam Zheng Reviewed-by: Eric Blake Signed-off-by: Kevin Wolf --- qemu-img.texi | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'qemu-img.texi') 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} -- cgit v1.2.1