Re: [Xen-users] cloning guests between Dom0's ?

[Simon Hobson <linux@xxxxxxxxxxxxxxxx>]

John Haxby wrote:

> > > For a LVM LV you can do the following (using the LVM snapshot) 
> > > without shutting down the domU:
> > > lvcreate -s /dev/vg/domU -L1G -n domU_snap
> > > mkdir /mnt/domU_snap
> > > mount /dev/vg/domU_snap /mnt/domU_snap
> > > tar cvjpf /storage/path/domU_snapshot.tbz /mnt/domU_snap
> > > lvremove /dev/vg/domU_snap
> > Is this correct ? I know the LVM snapshot will give you a "point in 
> > time" image, but won't the DomU have unwritten changes in it's 
> > cache - giving you a very unclean filesystem ?
> You probably want to use kpartx on the snapshot and mount the right 
> partition for backups.   However, as you'll say, you'll probably 
> come unstuck when you try to mount the file system because it will 
> be corrupt.  You need to cooperation of both the OS and any running 
> applications in the domU for this approach to work.  A good way to 
> get everything consistent for backing up is to shut down the guest 
> OS, take the snapshot and the re-start the guest OS.   Or at least 
> have the guest unmount the file system(s) you're going to back up 
> before you take the snapshot.
> Backing up data from a machine (physical or virtual) is surprisingly 
> difficult unless you can enlist the help of the machine.   It's 
> almost always easier to do it from within the machine.
Just checking I hadn't missed something !

I agree, it's a lot easier to just do it from within the client, or 
to shut the client down.

--
Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
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