My iMac desktop has Flash/SSD (late 2019).

Previously, I had an iMac with just the standard hard drive (not Fusion or SSD). Whenever a new OS was released, I would do I clean install i.e. backup my Home Folder, secure erase the drive, install the new OS, and then migrate my Home Folder contents (as per instructed).

I like the idea of cleaning up any straggly bits and take the drive back to its factory condition before installing a new OS. Is there some form of similar Clean Install routine for my current hard ware? Is that something which no longer can be done OR no longer is necessary?

I have seen this repeated elsewhere on this site and on the Internet: " …modern SSDs also have a fixed number of write cycles. A wiping operation would lead to several reads/writes on your SSD, making it prone to damage and reducing its lifespan."

Because of the very nature of the APFS file system and the nature of Solid State Media, a simple erase of the drive is considered sufficient. However the equivalent of the Erase and Install (a.k.a. nuke and pave) can be accomplished by

1. Being very sure you have a viable backup of your applications, data, and settings in Time Machine, another drive, or system just in case.
2. Boot into the Recovery Drive (from a cold start, hold ⌘R on Intel Macs or Press and hold the power button on Macs with Apple silicon)
3. In the Recovery Assistant launch Disk Utility and erase the target drive to APFS with a GUID partition scheme. A simple erase (recreating the directory) is all that is really needed unless it is known that your system has had the launch codes for the strategic nuclear weapons or similar informatIon on it. Quit Disk Utility.
4. Launch Install/Reinstall MacOS and install it on the blank drive (Note: an internet connection is required)
5. During the install process you will be offered the opportunity to recover your third party applications, User settings, user files. But if you are going to do that you could just as easily omitted step 3 (erasing the drive) and just do a Reinstall which will result in a clean new version of everything except the data volume and its contents.
6. If you want a truly pristine install and have a lot of time and patience, you can skip the Migration Assistant and manually reinstall all of your applications and recreate all of your settings and data yourself.

Thanks a heap! Just the exact guidance I was looking to find.



So . . . . Unless I plan to do #6, there is no point in doing anything other than simply upgrade to BIG SUR (i.e. using the Apple ICON/System Preference/Software Update menu)?


P.S. I would do #2 and #3 in a case where I was selling or discarding the iMAC?

That is the approach I have taken for several years now and as far as I can tell it is safer and more reliable in MacOS 11 (Big Sur) than it ever was in MacOS 10.x.
Yes, but stop an power down at the point where the system prompts for your language preference. Let the new user start there just as they would if the machine was fresh from Apple's orchard.

Thanks for the help.

Well, my approach has always been the same, and I just did it when installing the latest version of Big Sur, V11.1, onto an APFS-formatted partition on my (new) Samsung T7 1 TB external SSD (two other partitions on it are formatted as HFS+):

1. On my late 2018 Mac Mini running the latest version of Catalina, downloaded the Big Sur full installation file. It of course wound up inside my Applications folder.
2. Copied that file to another location on my internal SSD, and then deleted the one inside the Applications folder. What that means, of course, is that by launching it from another location, it will not get deleted.
3. Attached the 1 TB Samsung SSD to a port (USB-C) on my late 2018 Mac Mini.
4. Navigate to the location of that V11.1 Installer file, launch it, and proceed to do a clean, fresh installation of Big Sur onto that partition on the external SSD.
5. As usual, am offered the opportunity to migrate files, folders, settings, etc. from either a Time Machine backup, another backup, or a Mac. I chose "a Mac", and pointed to my Mac Mini.
6. Everything proceeded flawlessly regarding that migration.
7. Finally, restarted my Mini from that external partition, and as expected, it worked.

The primary purpose for me doing this now is to test Big Sur, as three of my critical applications are not yet compatible with Big Sur. Been testing for 2 days, and so far, all is well.

In actuality, when I do make the final move from Catalina to Big Sur (most likely in January or February, and that depends on when Tech Tool Pro will have a version ready for Big Sur), steps 1 and 2 will be the same. Then, will proceed as follows:

3a. Attach one of my Samsung 850 Pro 512 gig SSDs (enclosed inside an Orico enclosure) to the respective machine (I have 2 Macs: the Mini, and an early 2017 Mac Book Air).
4a. Run Onyx (Catalina version) and Tech Tool Pro on the respective machine.
5a. Do a SuperDuper! backup to the applicable partition on the external SSD.
6a. Restart the Mac from that just completed SuperDuper! backup.
7a. Launch Disk Utility there and Erase and Format (as APFS) the internal SSD on the respective Mac.
8. From there, repeat steps 4 through 7 above, except of course I'd be restarting from the respective internal SSD.
9. Remove the Catalina version of Onyx, and install the Big Sur version (in case folks do not know, that came out on Monday, and works fine, as expected).
10. Finally, launch Tech Tool Pro, and create the eDrive.

All of that has always worked flawlessly for me, and I wind up with a clean, stable system.