On Tue, Jan 31, 2006 at 10:56:13AM +0100, Geert Uytterhoeven wrote:
> 
> I saw a similar thing when the disk of my backup server died last month.
> The machine ran Debian testing, and I used an Ubuntu Live CD (the Knoppix I 
> had
> lying around didn't support SATA) to do the restore.
> 
> After the restore, some services didn't work because some configuration files
> were owned by the wrong user.
> 
> I ended up comparing the uids and gids in /etc/passwd and /etc/group on the
> restored image and on the Ubuntu Live CD, and for all differences, manually
> verifying all uids and gids of all restored files and directories. Fortunately
> this took much less time than expected :-)
> 
> I noticed one very strange thing though: uids and gids were not changed in a
> consistent way: some files had the incorrect uid or gid from Ubuntu, while
> other related files that should have the same uid/gid had the one from the
> original system. So sometimes uids/gids were remapped during restore, but not
> always...

My understanding, subject to correction, is that by default guntar
restores by trying to match text names (user and group) between the
archive and the recovery system.  If a match is found, then the
restore is to the numeric uid/gid of the recovery system, thus
matching the names, but not the necessarily the numeric ids in the
archive.  If matching text names are not found, then the archive's
numeric ids are used.

So you could easily get a real hodge-podge of names and numeric ids
by recovering to a different system.

   Archived System       Recovery System        Result of Recovery
     name   id #          name     id #            name    id #

     AAA    111           AAA      111              AAA    111
     BBB    222           BBB      234              BBB    234
     CCC    333          (no CCC) (no 333)         (none)  333
     DDD    444          (no DDD) (EEE is 444)      EEE    444

Note, 3 of the 4 cases result in a recovery that doesn't match the
originally archived system.  May or may not be what was wanted.

If the --numeric-owner option was used, only the second case would
change, the recovered result using an id of "222" rather than "234"
with a text name of either "none" or whatever name matchs id "222".

-- 
Jon H. LaBadie                  jon AT jgcomp DOT com
 JG Computing
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