Linux System Recovery part 1

In December 2012, there was a power outage mostly due to blowing fuse at the fuse box. For those that don’t deal with that much, older fuses will trip because the connectors are worn out. Also on a 20amp fuse you should not go over 60% output, so 14amp would be safe. You can replace with new fuse, to minimize this problem, and of course buying a uninterrupted power supply (ups) would mitigate the system turning off and on while we figure out why the fuse is being tripped.

System Crash
System won’t boot. It says that root partition is not available. Unable to load or mount any of the file systems. Looks like all the mount points are gone, or unable to read.

System Rescue

In Debian rescue live CD

#Scan for mdadm device
mdadm –examine –scan

#Update mdadm.conf with what what found
mdadm –examine –scan >> /etc/mdadm/mdadm.conf

#Assemble the raid. Examine scan should show you the name it wants you to use if different them md127
mdadm –assemble –scan /dev/md127

#See what got assembled
cat /proc/mdstat

#Now If you have LVM2 then need to mount LVM

#See if there is LVM group on your newly mounted mdadm device /dev/md127 for example.
pvscan

#Display more about the LVM2 group
vgdisplay

#See what logical disks are there(The /dev/md127 should match to what you found in prior commands)
lvmdiskscan

#Display the drives in md device
lvdisplay |more

#Display the list of volumes
lvscan

#Now we should have our raid device assembled and we should know a list of lvm drives(partitions) on the
#lvm group. We should see from lvscan what are their mount points

#if the lvm group shows inactive you can activate it by

#lvscan shows…Example
#inactive /dev/my_lvmgroup/my_root
#inactive /dev/my_lvmgroup/my_home
#inactive /dev/my_lvmgroup/my_swap

#Then do this. This will change the inactive status to active.
lvchange -a y /dev/my_lvmgroup

#You can deactivate the group but make sure all drives were unmounted by you running command umount on it.

Now that we have mounted the drives its time to recover. First we need to find out what file system are on our /dev/my_lvmgroup/my_root and /dev/my_lvmgroup/my_home. Then we need to do a file system check, and calculate our damages.