One simple possibility would be to use backuppc-fuse to mount the pc
tree and then use normal *nix routines like diff or cmp to find
differences.

If you only care to know which files differ, rather than how and if
you are using the rsync/rsyncd transfer method you could write a
custom perl routine that compares the md4 rsync checksums to look for
differences. Note md4 checksums are appended to cpool files after the
file is backed up a second time, so the routine would need to be smart
enough to default to comparing the entire file if no checksums exist.

More generally, if you are looking for maximum speed/robustness and
you want to take advantage of the pool structure, write a routine that
recurses down the 2 backups doing the following:

1. If file exists only in one backup --> different (VERY FAST)
2. Otherwise, if both files link to the same pool file --> same (VERY FAST)
3. Otherwise, if files link to pool files with different stem --> different 
(VERY FAST)
4. Otherwise, if files link to same pool stem with different suffix:
   First compare file size (from attrib file) (FAST)
   If same and and rsync checksums exist on both, then compare checksums (FAST)
   Otherwise, compare the *compressed* payload (STILL FASTER than decompressing)

Assuming that most files are unchanged, you will rarely need to do any
actual file compares. Even when you do, it will be sped up either by
using rsync checksums or by comparing the compressed files directly.



N.Trojahn wrote at about 14:09:06 +0200 on Friday, March 30, 2012:
 > Hello list,
 > 
 > I'd like to find the differences between to backups of a certain host
 > without restoring the two backups (way too large) and diff 'em.
 > 
 > Anyone has an idea how to achieve this using a script or something like
 > that which runs over the BackupPC pool?
 > 
 > Thanx in advance!
 > Falko
 > 
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