How best to do a clean install?

My Mac installation has migrated through many system updates and changes of computer, and has developed some issues, such as Safari reappearing after quitting and some other things, none of which occur in a clean account. So, when I come to install Sonoma (whenever that may be), I was wondering what the best approach would be, as there is obviously some cruft in my files that it would be nice to get rid of.
The Take Control books talk of a clean install, but use the Migration Assistant to copy the files. There is some selectivity possible, but I don’t know what files are causing problems, or what is necessary and shouldn’t be ignored.
Is there a method that will be relatively painless in transferring my data, while being selective about things like Launch Agents and Launch Daemons, plus assorted things in ~/Library?
This is likely a once in 25 years type of thing, so I expect it to take a while, but looking for advice to make it easier.

just did this on my '18 mini. Not cause I wanted to, but because a couple of dailys were not launching.
It was no party coz one of my main apps is Pro Tools.

!st off, many apps have settings you should write down, even if you use TM, CCC or other.
I didn’t write enough down, but I sure have this time.

After a total wipe, I installed from a fast bootable USB thumb.
I did not use MA as I obviously had a problem with some kind of corruption that I couldn’t pin down prior to the nuke and pave.

After the OS reinstall (Monty), one by one I installed (not d&d) my most important apps and made a dated spread so if I had I fail, perhaps I could id it this time.
Thus far all is well.

I d&d’d docs from an iDrive b.u.
I left many lesser PT plug ins behind as that’s where my suspicions lie.
As well as numerous ood or seldom used apps.
I have picked up about 150G of space.

YMMD, but take you time and make notes.

I do not use TM as it has caused issues in the past.
I use CCC monthly instead and, as I said, iDrive cloud 3x/week.

Here’s what I mean by notes:

wipe USB thumb with DU and format APFS.
Eject USB and re-insert if it won’t wipe.
launch Monterey installer and direct to USB thumb.
Restart with option held.
Select USB
About 20 mins.

Keyboard prefs:
disable caps lock
Use F keys as standard function
ShortCuts - Finder/empty trash Cntl/esc
Home/View/Show View Options (Command-J); check box to show Library folder.

Karabiner: Complex mod/add rule/enable caps-lock to cmd+cntl+opt+shft
QuickSilver: launch CapsLock/Tab
Shelf/Show Cntl/Cmd/L
from Catalog/User - make a copy of Documents folder that will end up in custom.
set Source option depth to 5
Enpass: Docs
TypeIt4: App Support/User, serial
ProTools: QS F15
Think or Swim: d&d Backup and workspace(s)
Firefox: QS F12
c&p ~/Lib/App Support/Firefox/Profiles & profiles.ini
CopyQ: github
Utilities from b.up
Mail: View: show Favs, Date & Time,
Import: User/Fritz/Library/Mailbox with largest Archive,
d&d - Data/Signatures
Keyboard shortcuts: Send, From, Date
c&p from ~/Lib/Mail/V#/MailData/Signature folder & SyncedRules.plist
QS Caps Lock + M
Prefs/View/Show Most Recent Message at Top
d&d: Photos, Movies, Docs, DLs,
reinstall MoneyDance
~/Library/Containers/com.infinitekind.MoneydanceOSX/Data/Library/Application Support/Moneydance/config.dict
/Users/Fritz/Library/Containers/com.infinitekind.MoneydanceOSX/Data/Library/Application Support/Moneydance/

Of If I was going to do this…and absent some strangeness or a known issue that’s a pretty big if…

Clone the entire drive to external
List all apps to be installed and have installers on hand or available if it’s things like Adobe cloud. Include serial numbers and activation keys and such.
Nuke the drive and install Sonoma, creating an admin account only (your daily driver is not an admin account, right…because it shouldn’t be.
Copy your existing homedir for daily driver account to /Users from the clone
Create daily driver account using same account name and tell it to use the existing homedir when asked. This will fix all the permissions.
Install apps…and only install the ones you’ll actually use.

You could create a new homedir instead in the new daily driver account step…but then all the prefs, settings, customizations, etc will need recreating and absent some issue I would not choose that approach.

This will be less painful, but I wouldn’t go so far as to call it relatively painless unless your definition of relatively is different and a lot less stringent than mine.

I wrote about this a while back.

Sounds like you aren’t in any hurry to upgrade, so in the meantime, you shoud try re-installing your current macOS from recovery to see if that will cure any of the issues you are seeing, assuming you have not done that yet. Will give you a clean System without disturbing any of your apps, user data and most all settings.

Thanks for all those thoughts. @ace, I’d forgotten the article, so re-reading that was helpful, and it’s probably the way I’ll go.

@alvarnell I’m not clear if that will do what I need. Nothing is a real show-stopper for me, so I’m leaning towards waiting until I move to Sonoma (I was in Sonoma County a few months ago for my nephew’s wedding, but I can’t afford to move there physically!) to avoid going through the long process twice.

This article by Howard Oakley of Eclectic Light might help:

How to clean install modern Macs

Reinstalling from Recovery isn’t a long process at all. Just boot into Recovery and choose to reinstall macOS. Takes approximately the same amount of time as a macOS update from there. No need to re-install anything else as they are left untouched.

I had some time today, so I thought I’d try the reinstall option. After ensuring that I have two good backups, I did the shut down and restart into Recovery. I got as far as selecting the disk for the installation, chose the internal disk, and got the message “The volume cannot be downgraded.” What next? I seem to be able to reinstall to the external disk, but that won’t really help.

I haven’t done this before, but according to How to ‘clean’ install modern macOS – The Eclectic Light Company, you have the following options. From least-to-most destructive:

  • Use the macOS “Erase all content and settings” option. This will wipe everything except for macOS itself, restoring your Mac to the state of a newly-purchased one, ready to start from scratch or restore data from a backup.

  • From Recovery mode, use the Reinstall macOS feature. But this can’t downgrade anything, as you found out.

  • From Recovery mode, wipe the System and Data volumes from the macOS APFS container. Then you should be able to clean-install macOS.

  • Use DFU mode to wipe everything. This will replace your firmware and erase the boot volume group, starting clean. Since you’re not yet running Sonoma, you’ll need another Mac with Configurator 2 in order to do this.

The article doesn’t mention deleting the macOS APFS container (or deleting all the volumes from that container) before a macOS reinstall. So maybe that’s not a viable option. But that’s probably not necessary. Simply deleting the System and Data volumes should be sufficient.

I think that this takes me beyond the quick system reset that @alvarnell suggested, so I will wait until I have the time to do @ace 's level 2 clean install with Sonoma.

Once caution. In the past I have done used migration to configure a new Mac, and that has worked very well. When I got a new macStudio, however, since I was moving from an (Intel) iMac Pro to a M1 system, I decided to do a clean install, with a manual configuration of the new system. In the process, something went wrong with iCloud synchronizaiton and the new Studio Mail (empty) was taken as the new “standard” and synchronized via iCloud to my other Macs resulting in the loss of a lot of archived email. I don’t know what happened - no warnings or error messages - and I was able to restore most of the lost email - but now I have a Mail database backup running and I am not inclined to do a clean install again!


That must mean that something went wrong with your last update if Recovery is trying to downgrade your current OS. It should know what you are currently running and re-install that version. I’ve done that several times and never had a problem.

Re-installation can also be accomplished by creating a bootable thumb drive with a full installer of the version you are running, but it’s a bit more complicated than using Recovery and requires a thumb drive.

Yes, I thought it was weird that it refused to downgrade, when it was supposed to be reinstalling the same version. Another reason to do the clean install when it’s time!

Following up, I did the level 2 clean install this week. The morning was done with backups and installing, and the afternoon with installing the applications, though I took the opportunity to leave out ones I don’t think I have a need for. I did keep a record of everything I had in the Applications folder and its subfolders, so I can go back for them if I need to.
Two full days of testing and work later, things seem to be working correctly. I no longer see the zombie Safari turning up, and another bug that was hanging around without a proper diagnosis doesn’t seem to trigger now, so I will call it a win, and a whole lot less painful than I thought it might be.


A sad follow-up. After weeks of being good, the zombie Safari is back. I run Safari for something (my main browser is Firefox), quit, and then some time later I see that Safari is running again, often without any open windows. Nobody had any good ideas why that was happening when I first mentioned it a few years ago.
Also, the other bug was solved, when I found that I had a setting on my computer that showed autolayout issues, which it turns out happen in the Save panel, and having that setting on caused it to crash in certain circumstances.
So, the reasons I wanted to do the clean install seem to have been unaffected by doing it, so I just have to live with occasionally quitting a zombie Safari…