For a couple of years I have been using Xen on my file server to run various Linux virtual computers. Initially I started by running it on Ubuntu, but when Ubuntu dropped support for Xen kernels, I moved to Debian Lenny and then Debian Squeeze.
Recently I bought a couple of HP Proliant Microservers . One of these was to replace my current server and the other to use as a firewall and run a couple of VM's. Transferring my main Xen server to the new box was easy. However, have been having problems setting up my firewall box.
My firewall box has two wthernet cards. One connected to my internal network and the other connected to an ADSL modem. Installing Squeeze and Xen worked fine, up to the point when I tried to configure pppoe. The configuration went OK, but when I rebooted Xen complained about eth1 (my internal interface) being busy or unavailable. The Xen wiki suggests removing all non essential ipv4 settings from your /etc/network/interfaces. However, mine was already pretty bare and basically identical to that on my other Microserver, which was working fine.
After re-installs I established that booting with the standard debian kernel worked fine. Both eth1 and my ADSL interface were initialized correctly. However, rebooting into the Xen kernel gave the same problem with errors about eth1 being busy or unavailable. he thing that caused the errors was configuring the pppoe interface. if I left it unconfigured everything worked correctly. Finally I decided that for whatever reason I wasn't going to be able to get Xen to work in this configuration.
I have never tried the virtualization already built into the Linux kernel (KVM), but decided to experiment to see how it worked for my requirements. Initially I tried installing Lucid, but ran into a problem where the installer couldn't install grub2 on my RAID1 boot disks. Rather fed up with problems by now I went with the latest Natty server, which installed without a problem.
There are several good documents about setting up KVM in Ubuntu:
- Ubuntu vm-builder
- KVM networking
- General Ubuntu KVM documentation
- Installing KVM on Ubuntu
After correcting an initial configuration error, I soon had bridged networking and a test VM with Ubuntu Lucid up and running.
Having successfully set up KVM, I think that I shall probably migrate my Debain Xen server to Ubuntu using KVM. Although Xen is working fine on that server, I don't really want to have to maintain two different network virtualization technologies.