I’ve been looking for some instructions on how to do snapshots on my machine. I did some research a while ago, and found several partial explanations, some of them contradictory.

http://arstechnica.com/columns/linux/linux-20041013.ars

goes through the whole process. He’s using XFS as the file system, so there is an extra step to freeze it. I suppose with ext2 you could remout as RO, but I thought the whole point of snapshots was to do this stuff hot!

Snapshots are a way to freeze your hard drive at a moment in time, usually for backup purposes. You basically end up with a read-only version of your hard drive on a separate device that you can back up, while the original version can tinker along.