<pre style="margin: 0em;">This helped me a great deal. Thanks. I just have a few questions... 1) is it best to unmount the /mnt/lvfoo/ before or after kpartx -d? because you have it in your procedure list both before and after kpartx -d. 2) is it possible to explore this dump file by either mounting it or some other method? 3) what is the best procedure to replace this dump file in case of a disk failure? i.e. just install xen and use virt-install? 4) is this the best possible method of backing up a domU? Thanks. Gerd Hoffmann wrote: </pre><blockquote style="border-left: 0.2em solid rgb(85, 85, 238); margin: 0em; padding-left: 0.85em;"><pre style="margin: 0em;"> Anne Facq wrote: </pre><blockquote style="border-left: 0.2em solid rgb(85, 85, 238); margin: 0em; padding-left: 0.85em;"><pre style="margin: 0em;">Because in Dom0 the device for a paravirt Domu (/dev/vg00/lvfoo in my case) is mapped to a virtual disk /dev/xvda (I created the Domu with virt-install), and the only way I found to mount this Domu filesystem, is to : - get the size of the boot sector of /dev/vg00/lvfoo (with fdisk -ul /dev/vg00/lvfoo) = 63 - compute the offset (multiply by block size) - specify this offset to the mount command : mount -o offset=32256 /dev/vg00/lvfoo /mnt/ </pre></blockquote><pre style="margin: 0em;">Uh, oh, quite complicated and error prone. Can be done much easier. Option (1): Use kpartx, it will create device mapper mappings for your partitions. Try "kpartx -v -a /dev/vg00/lvfoo", should give you /dev/vg00/lvfoop[1234]. "kpartx -d ... " removes the mappings. Option (2): (works only with xen kernel): Configure the device as virtual disk *in Domain-0*: "xm block-attach 0 phy:/dev/vg00/lvfoo xvda w". Gives you /dev/xvda[1234]. "xm block-detach ..." removes it. </pre></blockquote><pre style="margin: 0em;">Many thanks for this solution, it helps me a lot. </pre><tt>If this can help someone, here are the steps to backup a Domu </tt><tt>(filesystem on LVM in backend and on xvda in frontend) with the dump </tt><tt>command from Dom0 (Fedora 8), using one of the 2 solutions you advised, </tt><tt>kpartx : </tt><pre style="margin: 0em;">---------------------------------------------------------------- # The DomU named "foo" must be stopped before dump xm shutdown -w foo </pre><tt># Creates device mapper mappings /dev/mapper/lvfoop[1234] for </tt><tt>/dev/vg00/lvfoo </tt><pre style="margin: 0em;">kpartx -v -a /dev/vg00/lvfoo # Mounts temporarly the filesystem to backup mount /dev/mapper/lvfoop1 /mnt/lvfoo/ # Launches the dump /sbin/dump 0 -L FULL_foo -f /BACKUP-XEN/foo.colddump /mnt/lvfoo/ # Umount the filesystem umount /mnt/lvfoo/ # Removes the mappings kpartx -d /dev/vg00/lvfoo # Unmount the filesystem umount /mnt/lvfoo # The DomU can now be restarted xm create --config /var/lib/xend/.... ---------------------------------------------------------------- Regards, Anne Facq </pre>