I have automatic backup enabled and local TimeMachine snapshots take a large amount of disk space. This space is listed as purgeable in disk info, but cannot be actually used until the system decides to free it up. How can I force TimeMachine to delete those snapshots?
If you’re not running low on disk space (5 GB free) - just let this space be allocated as there is no downside to waiting to purge files until you need space.
That being said, if you decide to preemptively delete backups, I prefer to tell the system to free up space. If you know you have 50 GB amount to free, change the 5 below to 50 and then the system will iterate across all the local snapshots and prune them in the order defined by the system.
tmutil thinlocalsnapshots / $(echo "5 * 1000000000" | bc) 2
The only iteration I would do is to see how many APFS volumes you have and then perhaps thin any that are mounted.
Here’s a nice thread explaining the urgency - 2 works well for my needs, but the manual page explains there are 4 levels of urgency, so if you have specific needs, watch the IO and performance during thinning and experiment with smaller snapshots to thin.
In Terminal, enter the following command to list all backup snapshots:
tmutil listlocalsnapshots /
You will get a list of all the snapshots in the root directory (
Delete each snapshot by entering the following command + date of the corresponding snapshot:
sudo tmutil deletelocalsnapshots <snapshot_date>
sudo tmutil deletelocalsnapshots 2020-09-26-143409
Remember you can always get help with a command in terminal by entering the root command
tmutil -help to see all the Time Machine Utility commands, and usage instructions.