Extra Pepperoni

Time Machine has a hidden feature, to “Exclude All System Files”. In Leopard Server’s Standard mode, Time Machine is a service, and in Server Preferences you can control whether clients back up their system files, or skip them. This is logical — for personal backups you want everything, but if you have enough users to justify a file server, you might well not want to back up the same Leopard system files for each user.

Today’s handy-dandy discovery was that Mac OS X Leopard “user” has this feature too, but there’s no visible knob to turn it on. Interestingly, I cannot find such a control in Server Admin either, which could be my oversight or could simply be a bug (I’ve reported it, anyway).

Instead, if on the client you add /System to Time Machine’s list of directories not to back up (I also skip /Developer, /sw, and my music files), Leopard pops up a handy dialog, asking if you really want to “Exclude All System Files”. I chose yes, although I’d like to know exactly what (directories) are excluded by this option.

Server Admin’s Help has this to say:

Configuring Time Machine Backup Destination

Time Machine is a backup application that keeps an up-to-date copy of everything on your computer, which includes system files, applications, accounts, preferences, and documents. Time Machine can restore individual files, complete folders, or your entire computer by putting everything back the way it was and where it should be.

Selecting this option causes the share to be broadcast over Bonjour as a possible Time Machine destination, so it will show up as an option in System Preferences. On a standard or workgroup server, selecting this option also sets the POSIX permissions to 770 and sets the POSIX group to com.apple.access_backup.

A share point can be designated as a Time Machine backup in Server Admin.