FWIW, I am actually unable to reproduce this in a testcase. Mode
matches,
owner matches, freebsd 7, zfs, same rdiff-backup. Local root, remote
non-root. Would be interested to hear if anyone else has run into
this.
I have investigated further. Long story short, the problem is
triggered in
certain situations involving hard links. --no-hard-links makes the
problem go
away.
I have attached a small script which creates an "old" and "new"
directory
containing two files owned by root:wheel, with mode ---s--x--x. The
script
must run as root (but of course, don't run it as root without
looking at it -
even if you were to blindly trust it there are three things to
change in it
at the top).
In the "old" directory, the two are copies. In the "new" directory,
the second
file is hardlinked to the first.
Afterwards, the script runs rdiff-backup on old and then new. The
second run
bails with the error I have reported.