I’ve been using the freeware VMPlayer and VMware Server for a few years now, and while they function, it’s been a pain to have to recompile kernel modules every time the kernel is updated on my Fedora machines. A big disadvantage of VMWare is that the guests don’t seem to startup when run inside of an NX session, and I can’t run guests “headless” (without a monitor connected) using the free editions.
Based on the recommendation of [Craig Ozancin](http://www.linkedin.com/pub/0/826/810), I’ve tried [Virtual Box](http://www.virtualbox.org/), and I’m pleased with it — it lets me start and stop guests from the command line. I can connect to them using RDP (remote desktop). The new 1.4.0 release includes support for VMWare guest images! VirtualBox hasn’t required me to recompile kernel modules, and it seems to run faster than VMWare.
Goodbye VMware. Hello VirtualBox. What does the future hold? Probably [KVM](http://fedoraproject.org/wiki/Docs/Fedora7VirtQuickStart) (the [kernel-based virtual machine](http://www.phoronix.com/vr.php?view=9066)), which only works with newer Intel and AMD chips containing virtualization instructions.
I later discovered that when I (accidentally) ran the Xen kernel, VirtualBox wouldn’t work. It seems the Xen kernel doesn’t work well with third party virtualization solutions. It’s a good thing I don’t need Xen.