diff options
| -rw-r--r-- | Changelog | 2 | ||||
| -rw-r--r-- | qemu-doc.texi | 73 |
2 files changed, 70 insertions, 5 deletions
@@ -2,6 +2,8 @@ version 0.8.3: - 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: diff --git a/qemu-doc.texi b/qemu-doc.texi index 1e49ccfab3..9f0b4f68b4 100644 --- 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 +@item info snapshots +show list of VM snapshots @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 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. @@ -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 -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 +* vm_snapshots:: VM snapshots * 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). +@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 |