rdiff-backup is a commandline utility to backup one directory in another.
In my never-ending quest for "the thing that keeps accessing my disk", I finally did the obvious thing and looked at /var/log. That gave me quite a shock!
If you often switch your Linux computer with ext2 or ext3 filesystem on and off (for example because it is a laptop), it will check the filesystems at boot more often than necessary.
A problem I often had was this: I would switch off the wireless while using windows to get rid of the annoying blinking light, and after that it would stay switched off in Linux with no way to switch