Joe’s Amazing Technicolor Weblog

Because rsync 3 is one of if not the only OS X backup solutions that actually gets all the possible forms of metadata, I’m in the market for a backup solution that uses it. The current candidate is rsnapshot, a 6000 line perl program (!), conveniently located in macports, that wraps rsync to do smart backup things like keep snapshots via hard links. Thanks to the O’Reilly Backup book for pointing me to it.

• It’s pretty easy to set up to run locally. The main trick is that the configuration file requires tabs. First time in ~10 years I’ve had to turn tabs back on in vim (:set noexpandtab).
• For OS X, we want the magic -aNHAXx --fileflags --force-change args to make rsync behave properly with all the metadata.
• OS X has a weird directory structure, so if you try to backup /etc you just get the symlink that is to /private/etc, or if you try to exclude something under /var, you miss it because it’s really /private/var/bigdirectory. Buzzkill.
• Lchown.pm is necessary for symlinks to have the right ownership in snapshots. CPAN’d.
• Running things automatically on OS X as the privileged user is a bit odd, lacking as it does a traditional root account. Sudo does nicely, with NOPASSWD: /opt/local/bin/rsnapshot
on the backup machine. For the clients we need appropriate ssh settings, with some tricks to run sudo on the remote machine. Getting this running took a while, since I missed the fact that running rsnapshot via sudo on the backup machine meant that rsync would try to use root’s ssh key, not the backup user’s — fixed this with the -i arg to ssh.
• Restoring backups is just a matter of copying them from the appropriate snapshot dir, probably using rsync & the same arguments rsnapshot uses (easily extracted from the rsnapshot log).
• Multiple servers are done serially. If you wanted to run backups in parallel, you’d need one configuration file for every server you’re backing up, and they each need their own snapshot_root, logfile, and lockfile. For my installation, this’d be more trouble than it’s worth.
  

Another issue that temporarily gave me pause, now that we’ve got everything backed up with presumably correct permissions, is that our off-site backup procedures involve creating tar files & encrypting them. Fortunately, backup bouncer shows that OS X tar gets all the important stuff right, though it’s no rsync v3.

This entry was posted on Friday, October 31st, 2008 at 2:24 PM and is filed under Tech Stuff with tag(s) backup, os x, rsnapshot, rsync. Both comments and pings are currently closed.