Resolved Need instruction on how to take 2015 iMac back to original state

[TohMac]

Can anyone please point towards an easy to understand site explaining in detail how to take my 2015 iMac back to its original OS.

I made the mistake of upgrading to Catalina and wish to take it back to Mojave with a clean install. I haven't done a format since Macbook pros came with CD tray and disc.



Mojave

 

[Fishrrman]

I think what you'll need to do is:

- Create some kind of backup on an external drive

- Download the Mojave installer

- Use a 3rd-party app like "Install Disk Creator" or "DiskMaker X" to create a bootable USB flash drive installer of Mojave. (I believe you'll need a 16gb or larger USB flash drive)

- Boot from the flash drive, DON'T run the installer yet, instead close it and open disk utility, then...

- ERASE the internal drive to APFS, GUID partition format.

- Now quit disk utility and re-open the OS installer.

- Do a fresh install of Mojave. When it's done, go through the setup.

- At this point you can -try- to use setup assistant to migrate stuff from your backup, but if setup assistant won't do it, you'll have to do a "manual migration".

Plan on an entire day free to do this. Sometimes things go much faster, but then again, sometimes they don't.
Good luck.

Finally -- I hope you've "learned your lesson" about "upgrading" to "the latest and greatest" before taking a good look to see where such a "leap of faith" will land you...

 

[TohMac]

Thank you.

That does sound to be a lot more work than it used to be but I will follow that. As for upgrading, it was not my wish to have the latest as I was still using Sierra but ran into problems with the update process and unable to find the Mojave installer, rather than just the updates. Live and learn.


I have everything backed up. Just want a clean install of Mojave. Have important files backed up as well as on another mac.

 

[TohMac]

NM. Its a mess.

 

[satcomer]

Read the Apple Support article What to do before you sell, give away, or trade in your Mac