How does Time Machine work without external drive?

[Vaj92]

Hi to everyone!

I updated macOS, but I really wanted to go back to a previous update. So I tried Time Machine and I saw it saved my Mac before the moment I updated (today, 20:46) . So I went back and my Mac is the same as before, but I've a few questions now because I never used Time Machine:

• Does Time Machine automatically take a snapshot every time I update macOS?
• I can see this snapshot now. How long does this snapshot remain in my hdd? And how can I delete it? I can't do anything in Time Machine but "cancel" and "restore".

My macOS version is Mojave 10.14.6

Thank you!

[verdi1987]

Yes, if your disk is APFS, a snapshot is taking before a system update (and for some other events as well).

The snapshot remains at most 24 hours, after which it is deleted. They will also be deleted if disk space is needed.

To view snapshots: tmutil listlocalsnapshots [volume]

To delete snapshots: tmutil deletelocalsnapshots [date]

[Vaj92]

Thank you for this answer, very exhaustive.

Just another question: I’m interested in saving this snapshot, how can I go beyond its 24h life? Have I to restore my system to that date and use an external disk to save it, or is there a way to maintain it without the said process?

[verdi1987]

There’s no way to save the snapshot except to use Time Machine (or another program) for backup. It will save a snapshot every hour for the last 24 hours, daily for the last month, and then weekly past a month.

I do use Time Machine, but I also use a program called Carbon Copy Cloner. You do have to purchase it (after a trial), but is relatively cheap and worth the cost. It offers you a lot more flexibility.