duplicity --exclude-other-filesystems does not record mountpoints

[Rüdiger Kupper]

Binary package hint: duplicity

When using --exclude-other-filesystems, duplicity completely skips directories which are active mountpoints to different file systems. However, the backup will not contain any hint that the mountpoint itself ever existed.
Note that this significantly differs from the according rsync option "rsync --one-file-system", which records the empty directories as mountpoints.

Example:
When backing up the root file system "/", it seems wise to specify "--exclude-other-filesystems" to automatically exclude /proc, /sys and /dev. However, the backup then doesn't contain these directories at all, i.e., not even empty directories needed as mountpoints. Hence, the restored system will be dysfunctional unless all of the mountpoints are recreated by hand.
This makes using duplicity for system backups inconvenient and error-prone.

Moreover, since duplicity strongly advertises that it uses rsync's algorithm, one would expect it to behave like rsync does, when the according option "rsync --one-file-system" is used. Rsync then records the empty mountpoints, recreating a valid system upon restore.
Since duplicity claims to be similar to rsync this could be regarded a bug, at least a pitfall for all users used to rsync.

ProblemType: Bug
DistroRelease: Ubuntu 10.10
Package: duplicity 0.6.10-0ubuntu1
ProcVersionSignature: Ubuntu 2.6.35-28.50-generic 2.6.35.11
Uname: Linux 2.6.35-28-generic i686
NonfreeKernelModules: nvidia
Architecture: i386
Date: Sun May 1 20:24:27 2011
EcryptfsInUse: Yes
ProcEnviron:
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: duplicity

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[tdn (spam-thomasdamgaard)]

I agree that this is a bug and it should be fixed. However, it might be more useful to report it upstream.