info about VM snapshots

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@2096 c046a42c-6fe2-441c-8c8c-71466251a162

diff --git a/Changelog b/Changelog
index 693ce4ed3504d261e5ef916a4430fb90b62cfaae..8d36cbbe4a0298f35f2e3d76e31275b02f04488c 100644 (file)
--- a/Changelog
+++ b/Changelog
@@ -2,6 +2,8 @@ version 0.8.3:
 
   - Support for relative paths in backing files for disk images
   - Async file I/O API
 
   - Support for relative paths in backing files for disk images
   - Async file I/O API

+  - New qcow2 disk image format
+  - Support of multiple VM snapshots

 
 version 0.8.2:
 
 
 version 0.8.2:
 

diff --git a/qemu-doc.texi b/qemu-doc.texi
index 1e49ccfab3b72e7cb6b58f1900ed8dd888f5e7ca..9f0b4f68b404efc98b149ab3985b35e70deaab75 100644 (file)
--- a/qemu-doc.texi
+++ b/qemu-doc.texi
@@ -743,6 +743,8 @@ show USB devices plugged on the virtual USB hub
 show all USB host devices
 @item info capture
 show information about active capturing
 show all USB host devices
 @item info capture
 show information about active capturing

+@item info snapshots
+show list of VM snapshots

 @end table
 
 @item q or quit
 @end table
 
 @item q or quit


@@ -777,11 +779,18 @@ info capture
 @item log item1[,...]
 Activate logging of the specified items to @file{/tmp/qemu.log}.
 
 @item log item1[,...]
 Activate logging of the specified items to @file{/tmp/qemu.log}.
 

-@item savevm filename
-Save the whole virtual machine state to @var{filename}.
+@item savevm [tag|id]
+Create a snapshot of the whole virtual machine. If @var{tag} is
+provided, it is used as human readable identifier. If there is already
+a snapshot with the same tag or ID, it is replaced. More info at
+@ref{vm_snapshots}.

 
 

-@item loadvm filename
-Restore the whole virtual machine state from @var{filename}.
+@item loadvm tag|id
+Set the whole virtual machine to the snapshot identified by the tag
+@var{tag} or the unique snapshot ID @var{id}.
+
+@item delvm tag|id
+Delete the snapshot identified by @var{tag} or @var{id}.

 
 @item stop
 Stop emulation.
 
 @item stop
 Stop emulation.


@@ -895,11 +904,14 @@ CPU registers by prefixing them with @emph{$}.
 
 Since version 0.6.1, QEMU supports many disk image formats, including
 growable disk images (their size increase as non empty sectors are
 
 Since version 0.6.1, QEMU supports many disk image formats, including
 growable disk images (their size increase as non empty sectors are

-written), compressed and encrypted disk images.
+written), compressed and encrypted disk images. Version 0.8.3 added
+the new qcow2 disk image format which is essential to support VM
+snapshots.

 
 @menu
 * disk_images_quickstart::    Quick start for disk image creation
 * disk_images_snapshot_mode:: Snapshot mode
 
 @menu
 * disk_images_quickstart::    Quick start for disk image creation
 * disk_images_snapshot_mode:: Snapshot mode

+* vm_snapshots::              VM snapshots

 * qemu_img_invocation::       qemu-img Invocation
 * disk_images_fat_images::    Virtual FAT disk images
 @end menu
 * qemu_img_invocation::       qemu-img Invocation
 * disk_images_fat_images::    Virtual FAT disk images
 @end menu


@@ -926,6 +938,57 @@ a temporary file created in @file{/tmp}. You can however force the
 write back to the raw disk images by using the @code{commit} monitor
 command (or @key{C-a s} in the serial console).
 
 write back to the raw disk images by using the @code{commit} monitor
 command (or @key{C-a s} in the serial console).
 

+@node vm_snapshots
+@subsection VM snapshots
+
+VM snapshots are snapshots of the complete virtual machine including
+CPU state, RAM, device state and the content of all the writable
+disks. In order to use VM snapshots, you must have at least one non
+removable and writable block device using the @code{qcow2} disk image
+format. Normally this device is the first virtual hard drive.
+
+Use the monitor command @code{savevm} to create a new VM snapshot or
+replace an existing one. A human readable name can be assigned to each
+snapshots in addition to its numerical ID.
+
+Use @code{loadvm} to restore a VM snapshot and @code{delvm} to remove
+a VM snapshot. @code{info snapshots} lists the available snapshots
+with their associated information:
+
+@example
+(qemu) info snapshots
+Snapshot devices: hda
+Snapshot list (from hda):
+ID        TAG                 VM SIZE                DATE       VM CLOCK
+1         start                   41M 2006-08-06 12:38:02   00:00:14.954
+2                                 40M 2006-08-06 12:43:29   00:00:18.633
+3         msys                    40M 2006-08-06 12:44:04   00:00:23.514
+@end example
+
+A VM snapshot is made of a VM state info (its size is shown in
+@code{info snapshots}) and a snapshot of every writable disk image.
+The VM state info is stored in the first @code{qcow2} non removable
+and writable block device. The disk image snapshots are stored in
+every disk image. The size of a snapshot in a disk image is difficult
+to evaluate and is not shown by @code{info snapshots} because the
+associated disk sectors are shared among all the snapshots to save
+disk space (otherwise each snapshot would have to copy the full disk
+images).
+
+When using the (unrelated) @code{-snapshot} option
+(@ref{disk_images_snapshot_mode}), you can always make VM snapshots,
+but they are deleted as soon as you exit QEMU.
+
+VM snapshots currently have the following known limitations:
+@itemize
+@item 
+They cannot cope with removable devices if they are removed or
+inserted after a snapshot is done.
+@item 
+A few device drivers still have incomplete snapshot support so their
+state is not saved or restored properly (in particular USB).
+@end itemize
+

 @node qemu_img_invocation
 @subsection @code{qemu-img} Invocation
 
 @node qemu_img_invocation
 @subsection @code{qemu-img} Invocation