Binary package hint: duplicity
Duplicity restores user and group ids via lookup of user and group names. For this, it looks up the symbolic names from /etc/passwd and /etc/group *in the restoring system*. This is most often a good thing to do.
However, there are cases, where this can have devastating effect on the restored sysem, most notably, when restoring a system-backup of the complete operating system. Since this will usually be conducted from a different environment (most likely a live-CD), the restored files will "inherit" the numeric ids *of the rescue system*, rendering the restored system useless.
Rsync has an option "--numeric-ids" that tells it to skip the symbolic lookup and restore the numeric ids as they were on the original system. Duplicity lacks such an option. Sadly, I did not notice until I tried restoring a system backup using duplicity.
The problem is also described here: http://lists.gnu.org/archive/html/duplicity-talk/2010-09/msg00033.html. The Workaround proposed in this post seems awkward and potentially dangerous for the restoring system.
Duplicity cannot be sensibly used for system backups without an "--numeric-ids" option. This option should be added, if possible. If not, the manpage should state a clear warning not to use duplicity for system backups. (In its current state, it seems to suggest right that in a note on excluding /proc, which is a minor issue compared to not being able to use the restored system at all.)
ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: duplicity 0.6.13-0ubuntu1
ProcVersionSignature: Ubuntu 2.6.38-8.42-generic-pae 2.6.38.2
Uname: Linux 2.6.38-8-generic-pae i686
Architecture: i386
Date: Sat May 7 12:11:54 2011
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release i386 (20101007)
ProcEnviron:
LANGUAGE=en_US:en
LANG=en_US.UTF-8
SHELL=/bin/bash
SourcePackage: duplicity
UpgradeStatus: Upgraded to natty on 2011-05-01 (5 days ago)
Changing status to confirmed, as the post at http://