[Duplicity-talk] questions regarding duplicity's backup behavior in the event of a broken chain

[Shannon Collins]

Sorry if this posts twice- i sent it earlier but haven't seen it in the archives.

i have perhaps stumbled upon a duplicity bug that prevents a data restore, but i have questions regarding duplicity's behavior that might help me reassemble it.

Using Déjà Dup in Ubuntu 11.04, i created a full backup of my home directory on 20110911 to an external hard drive.  i made a series of incremental backups until 20120101 before reformatting my computer and doing a fresh install of Ubuntu 11.10.  

When i began the restoration process, i found that the "Restore from when?" dialog only listed dates until 20111028.  Upon inspecting the backup files, i discovered that the 20111029-20111116 incremental backup had 22 volumes but no manifest nor signature file, which broke the backup chain.  i don't know if the 20111029-20111116 backup volumes are complete- it may be that the backup was interrupted (i don't remember).

The subsequent incremental backups had the following characteristics:

 - start at 20111116

 - each manifest has no "Hostname" or "Localdir" lines

 - the volumes begin incrementing at 22

 - only the most recent (ending at 20120101) had a signature file

duplicity-full.20110911T222234Z                    vols 1-3203

duplicity-inc.20110911T222234Z.to.20110930T225238Z vols 1-5      +sig

duplicity-inc.20110930T225238Z.to.20111029T040635Z vols 1-62     +sig

(no manifest) 20111029T040635Z.to.20111116T003041Z vols 1-22     (no sig)

duplicity-inc.20111116T003041Z.to.20111116T033432Z vols 22       (no sig)

duplicity-inc.20111116T003041Z.to.20111212T172444Z vols 22-64    (no sig)

duplicity-inc.20111116T003041Z.to.20120101T171352Z vols 22-64    (no sig)

duplicity-inc.20111116T003041Z.to.20120101T192903Z vols 22-64    +sig

i was able to manually create a manifest for 20111029-20111116 and have been able to recover those files.  Unfortunately, there is an error (assert first.difftype != "diff", patch_seq) when duplicity is restoring 20111116-20120101 (duplicity seems to ignore the earlier 20111116* backups so i removed them from the directory) which i suspect might have to do with a missing signature for 20111029-20111116.

Here is where i could use some insight.  Perhaps the 20111029-20111116 volumes (and manually created manifest) are complete, or perhaps not; what affect would that have had on duplicity in the creation each subsequent backup (there were never any errors reported by Déjà Dup in this whole process)?  What would the manifest/signature for 20111116-20120101 be based on if there wasn't a signature for 20111029-20111116 available?  How might i create a signature somehow for 20111029-20111116 by based on a restore of date up until that point?  What is the relation between 20111029-20111116 and 20111116-20120101 in the light of the volume numbering, and the fact that it doesn't appear (from the volume data) that the latter is inclusive of the former?

Ultimately, i'm trying to recover my data, so if there's another angle i'm not aware of, please advise.  A corresponding thread at https://answers.launchpad.net/deja-dup/+question/183491 has more details if they're helpful.