[rdiff-backup-users] Backing up subsets of a filesystem

[Randall Nortman]

I would like to back up the entire filesystem on one schedule (e.g.,
daily) but subsets of the filesystem (mail spool) more frequently
(e.g., every 15 minutes).  Needless to say, I do not wish to consume
bandwidth and CPU cycles doing a full backup every 15 minutes, but I
would like to get the mail spool on that interval.  I would also like
to keep both sets in a single repository for maximum efficiency.

I attempted to do this by first backing up the entire filesystem (less
a few exclusions like /tmp) and then doing another backup with
"--include /var/mail --exclude /" added to the command line.  To my
dismay, this successfully backed up /var/mail but deleted everything
else from the destination repository just as if it had been deleted
from the source.  (Thankfully, I rsync my backup repository to a third
machine because I'm paranoid, and so I'm able to undo this mistake.)

Might I suggest that before deleting something from the destination,
rdiff-backup first check to see if the file would have been excluded
by the filters, and if so assume that it still exists (unchanged, due
to lack of information to the contrary) on the source?  Or is there
another way to do this, other than keeping separate repositories for
each subset?

Thanks,

Randall Nortman