UML brings back good memories from OS classes. We had to patch ext3 to add some triviality, and I did it first in UML so I could more easily test and make sure

UML brings back good memories from OS classes. We had to patch ext3 to add some triviality, and I did it first in UML so I could more easily test and make sure it was working correctly. It felt a lot faster and easier to setup than virtualbox or qemu (my options at the time), although I guess with hardware support and things like hypervisors it's no longer practical.