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[Qemu-devel] [PATCH 13/23] Documentation: Add qemu-img check/rebase


From: Kevin Wolf
Subject: [Qemu-devel] [PATCH 13/23] Documentation: Add qemu-img check/rebase
Date: Mon, 24 Jan 2011 22:10:42 +0100

Signed-off-by: Kevin Wolf <address@hidden>
---
 qemu-img.texi |   41 +++++++++++++++++++++++++++++++++++++++++
 1 files changed, 41 insertions(+), 0 deletions(-)

diff --git a/qemu-img.texi b/qemu-img.texi
index 1b90ddb..ced64a4 100644
--- a/qemu-img.texi
+++ b/qemu-img.texi
@@ -59,6 +59,13 @@ lists all snapshots in the given image
 Command description:
 
 @table @option
address@hidden 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} address@hidden
 
 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}.
 
address@hidden 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
address@hidden support changing the backing file.
+
+The backing file is changed to @var{backing_file} and (if the image format of
address@hidden supports this) the backing file format is changed to
address@hidden
+
+There are two different modes in which @code{rebase} can operate:
address@hidden @option
address@hidden 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.
+
address@hidden 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.
address@hidden table
+
 @item resize @var{filename} [+ | address@hidden
 
 Change the disk image as if it had been created with @var{size}.
-- 
1.7.2.3




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