HowtoMatrix

Here’s a guide to supporting Xen servers for people who are not
Linux experts. If your job means that you have root access to a Xen
server that someone else installed for the purpose of fixing problems
when they are not available then this will help you solve some common
problems.

Xen is a virtualization
system that is primarily used for running Linux virtual machines under
a Linux host. It is mostly used as a Paravirtualization system in that the virtual machine knows that it is running in a virtual environment - this allows some performance benefits.

The host environment is known as Dom0 and root in that domain has the ability to control the other domains (which are known as DomU domains). If you perform an orderly shutdown of the Dom0 (via the shutdown or reboot
commands or notification from the UPS of an impending power failure)
then when the machine is booted again the DomU’s will be automatically
restarted (if the on_reboot setting has the value restart - a common configuration). If you run the command shutdown in a DomU then the domain will be destroyed, and the command reboot
will restart the DomU with the same settings - if you want to change
the settings for a DomU you need to shut it down and create a new
instance.

The main sys-admin command related to Xen is xm. Here are the main xm options that are useful in support:

Read more at etbe