So something like the following, once a week:
Right. Maybe --exclude=/proc, as Bob mentioned.
du --one-file-system --human --bytes --separate-dirs / \
Better to leave out --human, since it's a lot easier for a script to
subtract two actual numbers than something like 2.1M
As long as you're doing a du of everything -- when looking for disk hogs
(wasn't that what we were talking about initially?), you need to know
the exact directory. I find GNU du's --separate-dirs option the most
useful approach.
The summary could be useful to see how usage changes over time, I
