Here’s a three-step process to create a Time Machine backup on a network-attached storage (NAS) unit.
- Create a sparsebundle image on your local system.
- Create and set permissions on your network share.
- Copy the sparsebundle to the network share root.
First, when you use Time Machine with a SMB disk, it creates a .sparsebundle disk image to put the backup data into. The disk image has a capacity of 2.75 TB. Since my SMB disk has only 1.5 TB of capacity, the disk image shows that 1.25TB is used and 1.5TB is available. The trick is to create another sparsebundle disk image of a given capacity (I used 300GB) on the SMB disk. Use ‘Mac OS Extended (Case-sensitive, Journaled)’ as the volume format in Disk Utility. Name the volume the same as the volume used by Time Machine (it should be Backup of computerName), and save it to something like test.sparsebundle.