How to Use macOS Time Machine via Terminal (tmutil)

Time Machine is widely considered one of the best consumer backup solutions ever created, thanks to its “set it and forget it” graphical interface. However, for system administrators managing fleets of Macs, or power users trying to script automated backup routines, the System Settings GUI is incredibly limiting. Fortunately, macOS includes a powerful command-line utility called tmutil, which allows you to control every aspect of Time Machine directly from the Terminal.

Step 1: Check Backup Status

If you are connected via SSH to a remote Mac and want to know if its backups are running properly, you can query the current status.

tmutil status

This will output a block of text. If the Running parameter is 0, no backup is currently in progress. If it is 1, you will see real-time data regarding the percentage completed and bytes copied.

Step 2: Start and Stop Backups Manually

You can force a backup to begin immediately without waiting for the next scheduled hourly interval.

tmutil startbackup

By default, this command returns you to the prompt immediately while the backup runs silently in the background. If you want the terminal to wait and provide progress updates until the backup is finished, append the --block flag:

tmutil startbackup --block

If a backup is running and is consuming too much disk I/O while you are trying to work, you can halt it instantly:

tmutil stopbackup

Step 3: Manage Backup Destinations

In enterprise environments, you often need to point a Mac to a network share (like an SMB server or a NAS) for its Time Machine destination, rather than relying on users plugging in USB hard drives.

To see where the Mac is currently backing up:

tmutil destinationinfo

To set a new network destination (you will be prompted for the SMB password):

sudo tmutil setdestination smb://username@server_address/ShareName

If you have multiple destinations configured and want to remove an old one, grab the ID string from the destinationinfo output and run:

sudo tmutil removedestination [Destination_ID]

Step 4: Exclude Specific Files and Folders

Video editors often have terabytes of scratch files that they do not want clogging up their Time Machine drives. While you can exclude folders via the GUI, tmutil allows you to script these exclusions.

To exclude a specific folder (e.g., the Downloads folder):

sudo tmutil addexclusion -p ~/Downloads

The -p flag ensures the exclusion is absolute and tied to that specific path. If you want to check if a file or folder is currently excluded, you can use the isexcluded command:

tmutil isexcluded ~/Downloads

Step 5: Calculate Space Requirements

If you are about to run a backup and want to know exactly how much data will be transferred (the “delta” between the current state of the Mac and the last backup), tmutil can calculate it without actually initiating the copy process.

tmutil calculatedrift [Backup_Drive_Path]

Alternatively, if you want to know how much space a specific folder on your Mac will take up on the backup drive, use:

tmutil uniquesize ~/Documents

By leveraging tmutil, you can incorporate Time Machine management into bash scripts, Jamf Pro policies, or simple cron jobs, giving you enterprise-level control over Apple’s consumer backup tool.