Reliability and robustness problems

[John Van Essen]

On Tue, 15 Jun 2004, John <rsync at computerdatasafe.com.au> wrote:
> 
> It may be that there will be files from different systems that are
> identical - think system binaries, fonts etc.
> 
> If these are in /var/local/backups/{host1,host2} etc, and I've run a
> script to identify these dupes and eliminate them using hard links,  can
> rsync preserve these hard links even though it can't see them all?

Yes and no.  Here are some examples.

Assume file A, B and Z are hardlinked on the source and on the target
and the source paths being synced includes files A and B, but not Z.

1. If there was no change to A and B, then there is no issue - rsync
   leaves them alone and all 3 files remain hardlinked on the target.

2. If A changes and becomes independent of an unchanged B, then the
   new A content is transferred as an individual file and B is left
   hardlinked to Z.

3. If A (and B and Z) change and remain hardlinked, the new content
   will be transferred, A and B will be hardlinked, and the hardlink
   with Z is now lost because rsync doesn't know anything about it.
   Z on the target now contains old content and becomes independent.
-- 
        John Van Essen  Univ of MN Alumnus  <vanes002 at umn.edu>