possibly new rsync trick: rotating snapshots

[jw schultz]

On Tue, Apr 09, 2002 at 04:07:49AM +0000, Mike Rubel wrote:
> Hello all,
> 
> I've found a simple, rsync-based trick to emulate the "rotating snapshots"
> feature found on some file servers, and hope that members of this group
> will find it useful and/or interesting:
> 
> http://www.mikerubel.org/computers/rsync_snapshots/
> 
> Snapshots are (or rather, appear to be) full backups of a system taken at
> regular intervals, available directly to users through a special read-only
> system directory.  When users accidentally delete or overwrite important
> files, or find themselves in need of an old version, they can copy from
> the snapshots without any sysadmin help.
> 
> Since I first saw the labor savings that automatic, rotating snapshots
> provide (relative to restore from incremental tape backups), I've been
> searching for a way to mimic them on my home Linux machine.  Rsync gave me
> a way to deal with the difficult part--making what are really incremental
> backups appear to be full ones.
> 
> Thanks in advance for any feedback or suggestions--
> Mike
> 
> 
> 

You headed in a similar direction to me.

In addition to the comments regarding NFS etc.  You will
find that with cp -l permissions and ownership will not be
accurately preserved in older snapshots if someone chmod or
chowns files on the original.

I have a complete system for automated rotating backups that
i was planning on announcing shortly (GPL).  I have been
using it for about a month so far and am quite pleased.
It is a little more complex than your approach and provides
more flexible rotation schedules with automatic image
(snapshot) expiration.

If anyone wishes to look at it or be an alpha test site
a periodically updated snapshot of the development area can
be found at http://www.pegasys.ws/dirvish.

It requires the --link-dest patch i submitted recently to
rsync in order to create the cross linking like cp -al while
preserving permissions.  A copy of the patch is at the URL.

I intend to make a more formal announcement when i feel it
ready for beta testing.

-- 
________________________________________________________________
	J.W. Schultz            Pegasystems Technologies
	email address:		jw at pegasys.ws

		Remember Cernan and Schmitt