What to do when a macOS update goes wrong – The Eclectic Light Company

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While macOS updates have become increasingly reliable, the more updates you install, the greater the chances of one of them going wrong. Because they can change components from the firmware to bundled apps and Safari, those post-update problems can include anything from kernel panics to Finder glitches.

Did you remember to back up before updating?

The single most important action you should take before starting any macOS update, no matter how small, is to check that you have a current backup. If you have Time Machine or a third-party equivalent set to make hourly backups, this should be no more than a quick check to ensure there’s a backup in storage that was made in the last hour. If full backups are less frequent then you may need to make a fresh one before going any further.

Another good habit of the past, running First Aid on your startup disk, should no longer be necessary, though. To do that properly you’d need to start up in Recovery and run it from there. This was almost essential in the years before journalling was added to HFS+, to ensure there were no minor errors that could escalate to a disaster in the update. With APFS First Aid is only indicated when you suspect there may be a problem with the file system of the boot volume group to be updated.

Boot loop

There’s one emergency situation that can happen on rare occasions if there has been a problem updating firmware: a boot loop, in which the Mac tries to start up, hits an early kernel panic, so tries to restart again, and continues in that loop. If that happens, press and hold the Power button until the Mac shuts down, and refer to this article.

Recovery Assistant (Tahoe and later)

macOS Tahoe introduced a new Recovery mode, Device Recovery Assistant. When your Mac has problems starting up correctly, it may start up in this new mode to perform repairs, and should also capture a sysdiagnose in the process. This is described here.

Restart, Safe mode

Otherwise the first thing to try is simply restarting your Mac normally. If that proves a problem, or things are still awry, try Safe mode. On an Apple silicon Mac, shut it down, wait ten seconds or so, then start it up in Recovery, select the disk to use for Safe mode, hold the Shift key, and click Continue in Safe Mode .

On an Intel Mac, hold the Shift key during startup.

Once running, leave your Mac for a couple of minutes, then restart in normal mode, with your fingers tightly crossed.

Sometimes Safe mode works fine, but as soon as you return to normal mode everything goes wrong again. That’s a good indicator that something you have installed is at fault, rather than the macOS update, although it’s often a combination of both working against one another. You now need to hunt down the third-party software that has become upset by the update, and either update or remove it.

If Safe mode either doesn’t help, or you can’t even enter it, then your Mac’s problems could be from the macOS update itself or something third-party, and teasing them apart isn’t going to be easy. This is when you should, for the first time, ask yourself whether you want to return to your previous version of macOS without the update, or try to fix what you’ve got. You can change your mind later, but this is a key question determining what you do next.

sysdiagnose for reference

In all more serious problems following a macOS update, now’s the time to gather evidence that could be useful later, particularly if you need to call on Apple Support. The best way to do this is to run a sysdiagnose, which captures the contents of your Mac’s log before relevant entries are removed, and adds to that detailed information about everything else that could be relevant to engineers investigating the problem.

There are three ways to create a sysdiagnose for a Mac:

Using both hands, press Command-Option-Control-Shift-. [period or stop] at the same time.

In Activity Monitor’s toolbar, open the … [ellipsis] menu and select the System Diagnostics command.

In Terminal, type the command sudo sysdiagnose, although I prefer using sudo sysdiagnose -f ~/Documents to save the archive in my Documents folder. You will be shown a stern warning and have to press Enter to confirm you really do want to create the archive.

Several minutes later, you should be shown where the sysdiagnose archive has been saved, normally in /var/tmp/ unless you use the -f option at the command line. Copy that to external storage if possible, so you’ll retain access even if the boot disk is completely erased when trying to fix the problem.

Missing files or apps

Rarely, you may discover that some files or even whole apps appear to have vanished from your Mac when it logs you back in after an update. In most cases, these have been moved to the Trash, and should still be there as long as you haven’t emptied it. It’s most unusual, though, for anything to simply...