Check first with: defaults read com.apple.systempreferences TMShowUnsupportedNetworkVolumes (should be 1). Yosemite and after appears not to have this requirement. Now just mount the “TimeMachine” Volume first and choose it as a backup disk in the Time Machine system preferences. Time Machine will create a sparsebundle disk image inside the volume and mounts that too. This is needed because the hard drive on your Ubuntu box is formatted as ext3 or Reiserfs and not the native Mac format HFS+. Because Time Machine backups everything to the disk image all metadata (like creation dates etc.) will be preserved. When your first Time Machine backup is done you can remove all Volumes and the next time Time Machine starts it will automagically mount the disk image from your TimeMachine volume on your Ubuntu box without mounting the whole TimeMachine volume |
Home > Server config >
On the Mac side you have to enable the option to use network volumes as Time Machine drives first. Without it your freshly shared and advertised network volume won’t show up in the disk selection dialogue in Time Machine. This is a hidden option not accessible via the graphical user interface so you have to copy & paste this in Terminal (it’s one line):