Kyle Lexmond
2010-Nov-14 10:13 UTC
[Xen-users] Recovering from VM file system corruption (in a LV inside a LV)
Hi list, Recently one of my VMs crashed, and couldn''t reboot due to filesystem corruption. It''s a Fedora 13 host, and I installed a Fedora 13 VM using virt-install, which by default creates an LVM for the root partition. Now, the partition that was corrupted was the root partition, so I couldn''t boot into the VM and recover it, like I would if /home was corrupted. Because I searched to mostly no avail how to recover a partition in a logical volume in a VM which itself is in a logical volume on the VM host, which the LV partitioned into /boot and the remaining space used for LVM, I''m posting the steps here, hopefully so someone in a similar situation can be helped. Step 1: Run kpartx -a /path/to/logical/volume For me, this was kpartx -a /dev/domU/helium. This created two block devices in /dev/mapper - domU-helium1 and domU-helium2. helium1 was my /boot, helium2 was used for LVM. Step 2: Run vgscan. This will give you a list of the volume groups on your system, hopefully including the volume group from your domU. Step 3: Run vgchange -a y volume_group_from_VM This will activate the logical volumes in the VG. Block devices should appear in /dev/mapper. For me, what appeared was vg_helium-lv_root.>From there, it''s a simple fsck /dev/mapper/vg_helium-lv_root. Wait forit to finish before you clean up after yourself. Step 4: To clean up, you have to deactivate the LVs before destroying the block devices that kpartx created. To do this, run vgchange -a n volume_group_from_VM . Step 5: Finally, run kpartx -d /path/to/logical/volume Hopefully this helps someone - Googling "Recover file system xen image" and variants thereof mainly turned up references to kpartx, not the necessary LVM stuff. The most helpful link was http://support.citrix.com/article/CTX117791, but it seems overly complicated and has XenServer specific tools mentioned. I''ll see if I can update the xen wiki too... _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users