Categories
XenServer

XenServer GrubConf.py fix script

In a previous article (Fixing XenServer error “Unable to find partition containing kernel”) I described how to fix a recurring problem after patching XenServer 6.2 installations. While the fix is known from years it’s never been adopted, and different distros (such as Ubuntu LTS 14.04) fail to boot properly when the GrubConf.py (on dom0) gets reset to its default state.

Being the lazy person that I am I decided to set up a script to do the work for me, after all we’re admins, not monkeys.

#!/bin/bash
GRUBCONF="/usr/lib/python2.4/site-packages/grub/GrubConf.py"
PATCHED=$(grep "_entry" $GRUBCONF | wc -l)
if [ $PATCHED -eq 2 ]; then
  echo "GrubConf.py is already patched"
else
  echo "Patching GrubConf.py to fix boot..."
  sed -i 's/_entry}":/_entry}":\n                        arg = "0"\n                    elif arg.strip() == "${next_entry}":/' $GRUBCONF
  PATCHED=$(grep "_entry" $GRUBCONF | wc -l)
  if [ $PATCHED -eq 2 ]; then
    echo "- Patch was applied successfully."
  else
    echo "- There was a problem while applying the patch."
  fi;
fi;
echo

This does just what I/we used to do manually: detects if GrubConf.py has been reverted and, if not, patches it up. Supplementary tests added for paranoia 🙂

Categories
XenServer

Solution to XenServer VM landing on initramfs

In my journey through XenServer lands, I once experienced a change in the UUID of the root partition, which resulted in a failed boot and being dropped into initramfs. Although this solution should have worked just fine, I either didn’t know of it at the time or it wouldn’t work for some reason.

While inside the VM initramfs I also had the pleasure of not having any text editor of sorts: no vi, no vim, no nano. Nothing at all. Even though I found the new UUID through the use of ls -al /dev/disk/by-uuid/ (and some guesswork), I had no way to edit the grub configuration. So, after some trial and error, I came up with the following:

(initramfs) mount /dev/xvda1 /mnt; cd /mnt
(initramfs) cp grub.cfg grub2.cfg
(initramfs) cat grub2.cfg | sed s///g > grub.cfg

After the proper root partition UUID was set in place, a reboot was all it took to set the machine back up and running.