[linux-lvm] Recovering from a disaster...
marco.shaw at nbtel.nb.ca
Thu Nov 28 07:04:01 UTC 2002
Going for my RHCE in a few weeks... Always wondered:
1. Are there any gotchas in a corrupted LVM volume? For example, /root/vg is an LVM volume, and either the 1st superblock on /root/vg or maybe the underlying /dev/sda1 partition or even /dev/md0 (assuming /root/vg could be sitting on top of a software RAID device) is zero'ed out. How does one go about fixing it? Will a simple fsck here work? But in the above case, is fsck run against md0 or sda1?
2. If one knows that /dev/md0 is in trouble (composed of /dev/sda1 and /dev/sdb1), but /dev/sda1 is fine, can one, upon boot, simply change LILO/GRUB from trying to mount root from /dev/md0 to /dev/sda1? My guess is no, since the disk label is different.
A typical scnerario could be LVM sitting on top of MD, and have to recover from some kind of disaster. I wonder if the RedHat 8.0 rescue option has all the modules/tools to repair such a disaster.
A co-worker just screwed up a system I suspect was setup with a combination of LVM and MD. I may have too quickly tried mounting /dev/sda2 (root on on disk), and maybe should have tried mounting /dev/md0. After trying to mount /dev/sda2 (with an raid autodetect type), I think mount complained about invalid options, so I proceeded to do an fsck on /dev/sda2, only to have mention something about the superblock (yes, I should write all the errors down), so I tried fsck on something like 32768,
and it started up... And ran... And ran. Result aftewards: all /dev/sda2 contains now after an attempt to mount it is "lost+found"! :(
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