During the Cyert Hall shutdown in May 2013, we discovered a xen crash due to serial port misconfiguration that causes an endless reboot cycle. This was observed on two 2850 dom0s running Debian Squeeze.
Procedure for solving:
- In grub menu, choose a non-xen kernel and edit the command line to remove all of the serial settings
Run dpkg-reconfigure setserial and choose manual configuration
Edit the file /var/lib/setserial/autoserial.conf
- Comment the ttyS# lines at the bottom of the file
Remove the line at the top of the file ###PORT STATE GENERATED USING AUTOSAVE-ONCE###
Disable the autostart services setserial and etc/setserial from the initscripts
- Reboot the machine