[CentOS] Backing Up A Xen Guest
graham at vpac.org
Wed Mar 28 02:12:10 UTC 2007
On Tue, 2007-03-27 at 08:48 +0800, John Summerfield wrote:
> Graham Jenkins wrote:
> > ..
> > The strategy goes something like:
> > * losetup -o 32256 /dev/loop0 /XenGuests/Guest1
> > * mkfs -t ext3 /dev/loop0
> > * mount -t ext3 /dev/loop0 /mnt
> > * cd /mnt && tar xjpf /tmp/Guest1.tbz
> > * for i in console null zero; do /sbin/MAKEDEV -d /mnt -x $i; done
> > * cd /tmp; umount /srv/vm1; losetup -d /dev/loop0
> > * xm create -c Guest1
> > And it always gets most of the way through .. then the guest dies.
> What does "most of the way through" mean?
Here's the last bit of what you see:
Loading ext3.ko module
Loading xenblk.ko module
Registering block device major 202
xvda: xvda1 xvda2
Creating root device.
Mounting root filesystem.
mount: could not find filesystem '/dev/root'
Setting up other filesystems.
Setting up new root fs
setuproot: moving /dev failed: No such file or directory
no fstab.sys, mounting internal defaults
setuproot: error mounting /proc: No such file or directory
setuproot: error mounting /sys: No such file or directory
Switching to new root and running init.
unmounting old /dev
unmounting old /proc
unmounting old /sys
switchroot: mount failed: No such file or directory
Kernel panic - not syncing: Attempted to kill init!
> Do those files have partition tables?
Yes, you can do: fdisk /XenGuests/Guest1 .. just like a real disk. It
was created by using virt-install to build a dummy guest before making
the new filesystem. Just two partitions .. / on ext3, and swap.
> Why not attach those volumes ro to another guest?
The theory here is that we should be able to recover an entire guest to
a new Xen host from a live tar backup done the previous night on another
night. Or would could recover to a larger container file if we needed
more room, etc. So recovering just part of a filesystem is useful, but
doesn't really achieve what we want.
I'm guessing that what we need to do is a 'chroot /mnt' then 'grub
--batch' somehow .. but grub doesn't want to know about disks with names
like /dev/xvda and partitions with names like /dev/xvda1 ?
Graham Jenkins +61 3 9925 4909
Victorian Partnership for Advanced Computing http://www.vpac.org/
PO Box 201, Carlton South, Vic. 3053, Australia
More information about the CentOS