[AuckLUG] What to back up?

[Johann Schoonees]

On the topic of back-ups again, my backup-rdiff script backs up the 
world because I couldn't be bothered excluding things and the back-up 
disks seem to fill quite slowly.  (From memory I exclude directories 
like /proc and a few others.)

However, in the interest of learning, what root-level directories could 
one exclude safely in the knowledge that one would never need them in 
the event of catastrophic distro update or hard drive failure?  /dev 
perhaps, or /tmp?

I had a disk crash recently and used the opportunity to change distros. 
  In the event only relatively few files from /home and /usr/local got 
restored from back-up, but I suppose having a good copy of directories 
like /etc might be a good idea?  What's your favourite list?

Johann