2

Given an upgrade from Mojave to Catalina:

Can my Time Machine backup be used to undo the upgrade (i.e, return me to Mojave), if something goes wrong?

hbquikcomjamesl
  • 914

2 Answers2

3

Yes and no

There is not a feature/function in macOS that will roll back patches (updates if you prefer) like can be done in Windows. But a Time Machine backup can indeed in assist you in rolling back to a previous update or upgrade.

Make sure you have a current backup of the system you want to upgrade. I would also make a USB installer of your current macOS version in the event that you want to roll back your upgrade.

See, what happens here, is that if you want to roll back a macOS upgrade, you need to boot from the desired macOS installer, wipe the drive, and reinstall the previous version of macOS. Then you use Time Machine to restore your data, settings and apps.

There is no uninstall for updates or upgrades like in some other operating systems. When you update or upgrade macOS there is no going back. So it is vital that you verify that all your current software is compatible with the new version you are updating to before you do the update.

Steve Chambers
  • 22,915
  • See https://apple.stackexchange.com/questions/271104/revert-to-el-capitan - I had a similar issue several years ago & Time Machine absolutely refused to restore to the older OS. There is also such as Mail, which is likely to change its database structure between OSes, which will also not revert. – Tetsujin Jan 12 '22 at 08:11

  • So it is vital that you verify that all your current software is compatible with the new version you are updating to before you do the update.

    There are very many reasons to want to undo an operating system upgrade that do not involve personal irresponsibility.

    For example, I just upgraded to Sonoma and immediately all my exFAT drives run 20 times slower. I have a fresh backup, I'd like to revert, but I can't.

    What is "vital" is the manufacturer, Apple, making sure their machines are always fit for purpose.

     – Tom Swirly Feb 20 '24 at 21:01
1

Get a big spare drive & make a bootable clone.

You cannot guarantee Time Machine will let you revert.

See Revert to El Capitan

Tetsujin
  • 115,663
  • 1
    Thankfully, the update-to-Catalina went far better than my scratch-install from two years ago did. Nothing broke, and the only glitches so far have been a few screwed up icons and a whole bunch of clutter I had to clean up in the Launchpad. – hbquikcomjamesl Jan 13 '22 at 23:52