Apple’s Time Machine software made it easy to setting up incremental back-ups, with one exception: network drives more formally called network-attached storage, or NAS. Time Machine only directly supports drives formatted with Apple’s HFS+J file system, and will eventually use all disk space on the drive. This page provides an illustrated guide showing how to set up Time Machine on a network drive, using a sparse bundle to emulate a smaller HFS+J drive. Click ‘show screenshot’ after each instruction to see the relevant screenshot.

via Time Machine on a network drive.