Panaceas: which general fixes still work well?

We all like a good panacea, something that fixes almost anything, without having to invest time and effort discovering what’s causing the problem. There are times when troubleshooting simply isn’t possible, or when simple panaceas are often the best. The trouble with panaceas is they’re like folk medicine: once they become popular, we continue to try them, no matter how little sense they might make. Here, changes in Macs and macOS over the last few years have made several traditional panaceas completely ineffective, or no longer possible.


This follows the generic principle of turning something off and back on again, which works so widely, and still holds good. It’s sometimes not tried when it’s most useful, for instance after updating macOS, when it can fix all manner of problems. On other occasions, rather than going through a full restart, we could be as successful with the more conservative and less disruptive action of logging out and back in again. Provided that the affected system runs for that user, that can prove just as good as a full restart.

A straight restart, using the Restart… command in the Apple menu, sometimes doesn’t prove as clean a break as the Mac needs. In some cases, it’s better to go through a cold boot by shutting the Mac down, leaving it for 10-20 seconds, then starting it up using the Power button. Knowing when to do that seems something of an art.

Safe mode

As a panacea, Safe mode is both underused and poorly understood. Apple’s description doesn’t help either: for example it states that “it also does a basic check of your startup disk, similar to using First Aid in Disk Utility”, although that doesn’t appear to be true of recent versions of macOS, which don’t check snapshots on the Data volume any more. That’s easily checked if Time Machine makes hourly snapshots on your Mac’s Data volume, as checking 24 snapshots takes an appreciable period, which would impose significant delay when starting up in Safe mode.

Starting up in Safe mode is also quite different on Apple silicon Macs. If you try holding the Shift key during startup on your M-series Mac, nothing happens at all. Instead you have to shut your Mac down, start up in Recovery, and there select and engage Safe mode, before your Mac restarts into the mode. This is an unfortunate side-effect of Secure Boot and 1 True Recovery.

Safe mode is most often used as a means of clearing system caches, thus a temporary measure before restarting in regular mode. There are good reasons for trying actions like installing macOS updates in Safe mode, though, which are often forgotten. Further details (M-series).

Reinstall last macOS update

Before Apple introduced the signed and sealed System volume (SSV) in Big Sur, it offered downloadable standalone updaters as Installer packages. With the SSV, macOS installations and updates are far more than can be put into an Installer package, and Apple stopped providing those updaters. Once your Mac has installed a macOS update, there’s no way of downloading and installing that update again, nor can there be any need, as I explain below. This panacea has passed into history.

Install the Combo update

For the same reasons, Apple no longer provides ‘Combo’ updates, consisting of a consolidated update capable of taking any previous version of that major release of macOS up to the current version. Combo updates are also dead and gone.

Reinstall macOS

After restarting, this used to be one of the most common panaceas recommended, usually when an advisor couldn’t think of anything better. Although it’s still widely recommended, even by Apple, it has now lost much of its rationale.

Reinstalling macOS used to work, when it did, because the files and folders that made up the system were just ordinary files and folders, and their integrity wasn’t checked. Errors could and did occur during macOS installation and updating, and despite the protection of SIP could occur at other times too. Some of the problems treated by reinstalling macOS undoubtedly arose because of those errors, so users accepted that as a useful panacea that did fix those problems.

The SSV is different. It’s not even a regular volume, but a snapshot of the System volume, and snapshots are immutable, as some of us know from bitter experience. Furthermore, every single bit in the System is verified in a tree of hashes. If the SSV no longer matches its hash tree, then macOS won’t boot from it. There are some differences in how thoroughly checks are made of this, but if your Intel Mac has a T2 chip, or it’s an Apple silicon Mac, you can rest assured that, so long as your Mac has full boot security active, it won’t tolerate any change or corruption in the SSV.

Verifying the integrity of the System is now easy: just restart. If there’s anything wrong, your Mac will tell you, and in the case of Apple silicon Macs will put the Mac into Recovery ready for macOS to be reinstalled.

So is there any remaining role for reinstalling macOS when a Mac boots normally into Full Security mode? I’d like to see rationale and results before continuing what should have lost all rhyme and reason. Details.

Clean reinstall macOS

Wiping your startup System and Data volumes and recreating them from scratch is different, and the only way that I know to tackle deep-seated problems in the Data volume and its firmlinks with the System volume. It’s a long process, and these days involves migration from a backup or copy of the Data volume. If all else has failed, it may be the only remaining option.


We generally like panaceas that are quick to apply, and minimally disruptive. Resetting, wiping or zapping the NVRAM is a perfect example, as it can be performed during a restart on Intel Macs. Details.

If you’ve got an Apple silicon Mac, though, it’s more controversial. Despite claims you might see, using the normal startup keys on an M-series Mac does absolutely nothing, and there’s no readily accessible feature in Recovery mode either. It might be possible to reset some of the unprotected parameters in the NVRAM in Terminal in Recovery mode, but I don’t recommend trying.

Reset SMC

In pre-T2 Intel Macs, this is a discrete component and another instant panacea with a proven track-record. The introduction of the T2 chip made this a bit more complex, but still of value in some cases. As Apple silicon Macs don’t have a discrete SMC, there’s no means to reset what doesn’t exist in them. Details.

Restore/repair/reset permissions

Once a popular panacea for Intel Macs, and recommended by Apple, this has recently all but vanished, although the Terminal command is still available in Recovery mode. Unless Apple documents it again and explains more, I wouldn’t recommend trying it. Details.

Hardware diagnostics

This isn’t a panacea as such, but a valuable step in diagnosing many problems that could be hardware-related. Don’t forget to use when appropriate. Details (Intel).

First Aid on the boot volume group

This is another valuable diagnostic step, and should whenever possible be performed using Disk Utility in Recovery mode, where checks can be run best. Remember that Apple recommends starting by running First Aid on each volume, then container(s), and finally the disk itself.

New User

Creating a new user to try to isolate problems thought to stem from something in the current user’s Home folder and settings remains a valuable diagnostic tool, although it doesn’t really solve a problem, merely helps you pin it down.

What’s gone:

  • Reinstall last macOS update
  • Install the Combo update
  • Reinstall macOS (in most/all? cases)
  • Restore/repair/reset permissions.

What’s left:

  • Restart
  • Safe mode
  • Clean reinstall macOS
  • Zap PRAM/NVRAM (Intel only)
  • Reset SMC (Intel only)
  • Hardware diagnostics
  • First Aid on the boot volume group
  • New User.