Time Machine Backups over WiFi

Leopard does not (yet?) backup to a disk attached to an Airport base station, to lots of people’s concern. But OS X version 10.5.1 will backup over the network – to another Mac. It works just fine over wired or wifi networks, so it works for MacBooks.

Initial setup is easy.

On the host Mac: Plug in your external drive. Turn on File Sharing from System Preferences (AFP, the default, is what you want). Share a directory on your external drive where you’ll store the backups.

On the Mac you want to back up: Mount the backup share. Then go to Time Machine in System Preferences, and turn it on. When it asks you for a backup destination, select your backup share.

Each time you backup…

Time Machine then needs two things before it will backup your MacBook:

  1. Plug the laptop into a power supply. Time Machine won’t start a backup if you’re running on battery power.
  2. Mount the share that holds your backups. (Double-click on it in Finder.)
  3. Done. Time Machine will back up on schedule, so you can keep working. But if you’re anxious, you can also start the backup by picking “Back Up Now” from the Time Machine icon.

I find these two steps to be much more convenient than plugging the external drive into the laptop, and I hope you will, too.

Update 31 May 2008: Since Leopard 10.5.3, Time Machine no longer requires any of this – it mounts backup shares when needed, so you don’t have to do anything. Once you get Time Machine working again, that is. If you’re having troubles since the 10.5.3 update, read A Fix for Time Machine on OSX 10.5.3 over AFP for .mac Users, a how-to that will get you going again.