Question on --backup --backup-dir Switches For Incremental Backs

[Paul Slootman]

On Mon 29 Jan 2007, Matt McCutchen wrote:
> On 1/29/07, Wayne Davison <wayned at samba.org> wrote:
> >If you
> >want to store the new, changed files, use one or more --compare-dest
> >options (one pointing at an old full backup, and an extra option for any
> >intervening incrementals).
> 
> This approach won't work because rsync will skip a file if it is in
> the same state now as in any of the backups, not just the most recent
> one.  Thus, if I change a file and change it back, the fact that I
> changed it back would not be recorded.

Well, you'd have to change the mtime etc. back as well, which is a
pretty unlikely scenario; but apart from that it's a good point.

Conclusion is that having only the changed files as an incremental
backup is a bad idea; consider also deleted files: how do you represent
that in an incremental...

(The old BSD dump / restore dumped a list of inodes as well, and hence
worked pretty well when using incrementals.)


Paul Slootman