Linux isn't the only technology you can access through LiveCDs. Because I've had such success with Linux, I thought I would test out LiveCD virtualization and share my findings in this review.
Two LiveCDs are available that provide virtualization with Xen. One is called Xenoppix, which comes from the Knoppix community and is available at the Xenoppix Website. The second comes from XenSource (commercial sponsor of the Xen technology) itself and is referred to as a Demo CD.
I thought my trial of the two LiveCD versions of Xen would be a piece of cake, but I found myself bedeviled with compatibility issues unlike any I've ever experienced with a LiveCD Linux.
Xenoppix – Neither Knoppix nor Xen
Xenoppix aims to give you the experience of having a Xen-enabled machine. In Xen parlance, it provides a Dom0 machine with the Xen hypervisor running underneath it. Based on that, you should theoretically be able to run one of the two included guest (DomU) operating systems that are included.
You might expect some version of Linux, but instead the two included operating system options are Plan9 and NetBSD. Essentially, Xenoppix attempts to mimic the experience of using Xen as if you installed a Xen-enabled Dom0 kernel and wanted to run some guests.
I was unsuccessful in getting Xenoppix to run on any of the four (yes, four) machines I tried it on (new dual-core Athlon desktop, new dual-core Turion laptop, Whitebox Athlon 3000+ and Intel-based IBM T23 laptop).
The first two hung at the video card stage of booting, which is perhaps understandable because Xenoppix might not have the latest drivers in it. On the whitebox, Xenoppix hung during the autoconfiguring devices boot stage, and on the T23, it loaded all the way but insisted on a 1600 X 1280 display resolution, which meant that all of the toolbars were off the display and rendered everything useless.
I should point out that the latest version of Knoppix ran flawlessly on all of these machines. What makes it especially irritating that Xenoppix didn't work correctly is that Knoppix manages to work on the machines and fits onto a CD in so doing, but Xenoppix requires a DVD and runs well over a Gigabye in size.
To be fair, I saw a posting on the Xen mailing list in the past day or so that indicated a new version of Xenoppix might be available in the near future (including guest Linux distros), so the situation might improve. Until then, my conclusion is that Xenoppix is not very satisfying.
Xen Demo CD
The Xen Demo CD is not based on Knoppix but rather appears to be a custom-built Debian-based system. Rather than providing a base-level "Xenified" running kernel upon which you can install operating systems, Xen Demo CD aims to demonstrate how a running Xen box works.
On first loading, the Xen Demo CD opens a window showing system statistics. A Web page outlines how to get guest operating systems up and running. Three guest operating systems are easily booted via a right click of the mouse. And each guest OS has a running virtual network connection (VNC) instance that allows graphical interaction. You can find the Xen Demo CD at the Xen Website.
I had high hopes for the Xen Demo CD after my experience with Xenoppix; after all, the Xen Demo CD comes directly from the creators of Xen. But while my experience with the Xen Demo CD was somewhat better than Xenoppix, I still found the product to be more challenging than an easy introduction to a topic should be.
When I tried to boot the Demo CD on the new desktop dual-core Athlon machine, a message ricocheted across my monitor reading, "Not optimum mode 1280 X 1024." The new dual-core Turion laptop issued an X window error message, but did offer a text-based interface to load guest operating systems. A text-based interface might be acceptable for some users but might be less than friendly for others.
On the Whitebox machine, the booting process brought a message that it was going to execute the Gnome display manager. It then went blank. My Whitebox machine has no graphics card; it uses the motherboard's graphical capability. Perhaps this defeated the Demo CD, but the product ought to be able to deal with this sort of configuration.
Finally, on the IBM T23, the Demo CD booted perfectly. I could bring up guest operating systems, view their status in the Xen status window and graphically work within them via VNC.
But the guests could not successfully obtain an IP address from the local DHCP server. One guest could obtain an IP address by executing "dhclient," but it seems like some robustness is missing.
Neither Xenoppix nor the Xen Demo CD delivers what Linux LiveCDs typically provide – an easy-to-run, easy-to-use introduction to a specific technology. But with a bit more work, these tools could offer a tremendous introduction to the very capable Xen technology.
In the meantime, LiveCDs can be a good way to dip your toes into the Xen water, but don't be surprised if you find a riptide. You'll need to take care to ensure you have a good swim with Xen.