After a hard disk failure in the office I am setting up a more comprehesive backup system.
The bulk of it consists of using rsync to periodically synchronise data on my workstation with NFS mounts.
Each time I run rsync, I want to check that the destination directory is within a NFS mount point (so that I don't run out of space duplicating the data on my hard disk if the NFS destination directory is not mounted for some reason). Below is a little script which does this (I use it in a Makefile with a target for each project).