1

I just upgraded from El Captain to Mojave and I have a Time Machine backup of the instant before starting the upgrade.

I need to be able to eventually restore the previous operative system, but I am afraid that that backup could be removed in order to make space for newer backups.

How can I "mark it" and ensure that that specific backup will not be discarded?

Kamafeather
  • 446
  • once you have let Mojave back up to the TM drive, you have lost the ability to roll back to El Cap from it. See https://apple.stackexchange.com/questions/271104/revert-to-el-capitan – Tetsujin Feb 18 '19 at 11:17
  • 1
    @Tetsujin Are you sure? I've rolled back to a previous OS several time using TM. Last time was c. Sierra, I think. – benwiggy Feb 18 '19 at 11:42
  • @benwiggy - having spent quite some time trying to do it, pretty sure. How did you manage to do it, wholesale or just piecemeal? – Tetsujin Feb 18 '19 at 14:37
  • @Tetsujin Boot to Recovery, choose Restore from TM, choose a snapshot. Bingo. https://support.apple.com/en-gb/HT203981 – benwiggy Feb 18 '19 at 15:45
  • Flatly refused when I tried it. – Tetsujin Feb 18 '19 at 15:50
  • @Tetsujin You should ask a question about it....!!! – benwiggy Feb 19 '19 at 08:25
  • @benwiggy - I'm no longer in a position to be able to test it. My last rollback, from my linked question above, was 18 months ago. I've been on Mojave since the first beta; I couldn't wait to get rid of the Sierras. – Tetsujin Feb 19 '19 at 08:28
  • If you tried on a beta could be that the restore feature was not stable/complete enough ‍♂️ – Kamafeather Feb 19 '19 at 12:07
  • What makes you think I tried it on a beta - you need to read the linked QA for details. – Tetsujin Feb 19 '19 at 13:22

1 Answers1

3

There is no way of marking a TM snapshot as being particularly important.

However, as long as the TM disk isn't full, then TM should not normally delete the snapshot that accounts for a complete OS change. (Assuming that you had the old OS on your disk for more than 1 month.)

TM will start deleting the oldest snapshots if the drive is full, to make space for the newest ones.

If you want to make absolutely certain, you would do well to use an app like SuperDuper! or CarbonCopyCloner to make a clone disk image, which you can restore at a later time. (But you needed to do this before upgrading.)

Bear in mind that when you roll the whole disk back, you will lose any changes to your data made since the rollback date. IMAP servers will handle changes to email, but documents and other files will need to be restored by other means.

benwiggy
  • 35,635