I'd like to create several virtual servers (all running linux) on my physical server. All of them will be used as headless servers - ie. they'd be the equivalent of an EC2 instance but running on my own hardware.
My host server is also headless - it's at a colo and I don't have it running X or GUI.
I'd like to use Ubuntu for both the host and the guest machines, and I'm hoping to make administration of machines (startup, suspend, shutdown) as easy as possible.
I have linux administration experience, but have not setup headless virtual machines before.
I've already started with KVM and have setup a virtual machine and have spent some time debugging it. I've also looked into Xen and am about to try Virtualbox. I'm trying to find out what experience the community here has had and what tools they've found most useful.
What are the best tools and methods for accomplishing this?