I have been following the tutorial referenced here. http://www.howtoforge.com/create-centos5.2-domu-on-ubuntu-hardy-dom0 Now there are lots of typos and errors in the tutorial, but I managed to overcome them. Upon creating the CentOS DomU, I do get a login prompt and can login. The first issue I had was that I couldn't get any updates or install packages. I thought it was a DNS issue. But after fixing that, I noticed I couldn't even ping. Typing ifconfig at the command prompt, I noticed that eth0 has a MAC address, but no IP. I did follow the tutorial on specifying the IP. I also tried specifying it in the Xen config file for the DomU. Regardless of which method I try, I get an error message upon starting the DomU that says another host already has claimed this IP address. I know for a fact that is not the case. I have changed the IP address too and no matter what I change it to, I get the same error message. Any ideas of where to look next?