[Feature request] loadvm snapshot as read-only
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
QEMU |
Expired
|
Wishlist
|
Unassigned |
Bug Description
There are many ways to take and manage snapshots in QEMU, but one main feature that's missing is the ability to 'loadvm' a LIVE snapshot and have all future changes redirected to a temporary file. This would effectively be combining the -loadvm and -snapshot switches and make the snapshot read-only. With this feature, users would be provided a "sandbox" and be able to start and restart the same live snapshot without corrupting the image in doing so.
I found a lot of discussion about this topic on the mailing list years ago, including some patch submissions, but none of the conversations panned out.
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What would it take for this feature to be added, and can we use the patches submitted by Eddie Kohler to enable this feature?
Changed in qemu: | |
importance: | Undecided → Wishlist |
On Sat, May 25, 2013 at 08:29:11AM -0000, Michael Coppola wrote:
> There are many ways to take and manage snapshots in QEMU, but one main
> feature that's missing is the ability to 'loadvm' a LIVE snapshot and
> have all future changes redirected to a temporary file. This would
> effectively be combining the -loadvm and -snapshot switches and make the
> snapshot read-only. With this feature, users would be provided a
> "sandbox" and be able to start and restart the same live snapshot
> without corrupting the image in doing so.
This should be possible soon. Wenchao Xia is working on new monitor snapshot- sync).
commands that allow you to combine internal snapshots (loadvm/savevm)
with external snapshots (blockdev-
You would submit a QMP 'transaction' command that specifies a loadvm snapshot- sync. This operation is atomic.
followed by a blockdev-
Note that internal snapshots do not destroy the snapshot. Therefore,
when you loadvm an internal snapshot and write to the disk, you are not
modifying the internal snapshot only the current state of the disk. You
can loadvm it again later.
Stefan