I’ve just learned that the usr directory on Linux/UNIX systems stands for UNIX System Resources. I always assumed that usr was an abbreviation for ‘user’. Another lesson here: never assume.

The second thing I learned is that there are two independent /tmp directories in Linux. One is simply /tmp, and the other is located in /var/tmp. The important thing I didn’t know before is that the contents of /tmp are deleted automatically after ten days, while files in /var/tmp are removed after thirty days.

These are basic concepts, but basics are important!

All of this was thanks to the Red Hat Enterprise Linux Technical Overview course – specifically the lesson on The File System Hierarchy. Huge thanks to Red Hat for making this material available for free (temporarily) at rh024 redhat.com