Can't downgrade to High Sierra

[bradley8795]

So I have searched for hours and hours trying to figure out how to downgrade back to High Sierra from the latest beta. I know exactly how to do it, but of course it is not working.

First of all I am on a 2017 27" iMac base machine. Currently on 10.14 Beta (18A353d)

I need to downgrade, because I was an idiot and didn't read that it may not work with some printers, well mine are on the list.

So basically what happens is I of course backed everything up, then boot into internet recovery. Open up disk utility and try to erase the disk. But it just won't do it, I let it set for a little over an hour, I've opened up the log, and it gets stuck on Erasing Disk (not the exact wording). It only takes about 5 seconds to get that far, but even if I leave it for an hour it will not go further. It also will not allow me to quit the disk utility, so I have to turn off the iMac by holding the power button, and it will boot back to Mojave.

I had the bright idea of setting up bootcamp to see if I could print in Windows, because I can't do it through parallels, well when trying to partition the disk it errors out, and won't continue. I have tried portioning it through both disk utility and the boot camp app.

I was, and still am fully prepared to erase and start over, knowing that betas have bugs. But at this point I can't even do that.

Any ideas?

 

[bradley8795]

Ok, update time. So still haven't been able to get the drive erased.

Created a USB installer for High Sierra. Installed High Sierra on a portable USB 3 drive. Of course it is horribly slow, but it is working.....for now. Just installed the printer software. That only took 30 minutes. But now I am back to being able to print. Just have to boot from the external drive to do it.

Crappy workaround, and it is painfully slow, and takes way to much time. But it is working, so that is the important part.

If anyone has any other ideas I am open to suggestions. I am assuming that the next beta release will fix it, and 2 weeks of dealing with this won't absolutely kill me, but I would definitely like to have the option to fix it if I can.

 

[Marcopolo53]

What I would do is 1 - remove beta profile from iMac 2- from the bootable USB 10.13.6 installation (Functioning) install CCC (latest version - 30 trial version) - then boot from USB 10.13.6 and use DU to erase the internal SSD / HD to HFS+ 4- use CCC to Clone USB 10.13.6 to Internal SSD/ HD 5 - set internal SSD/HD as startup disk

 

[bradley8795]

What I would do is 1 - remove beta profile from iMac 2- from the bootable USB 10.13.6 installation (Functioning) install CCC (latest version - 30 trial version) - then boot from USB 10.13.6 and use DU to erase the internal SSD / HD to HFS+ 4- use CCC to Clone USB 10.13.6 to Internal SSD/ HD 5 - set internal SSD/HD as startup disk

I actually tried that last night. When in the external hdd OS I can not partition, or erase the internal hdd. DU sees the internal HD, and will attempt the process, but it will never complete. Just sits at deleting volume for as long as I will allow it to.

I was wanting to just do a completely fresh reinstall of High Sierra, and I am not worried about a backup with CCC because I have everything I need backed up in at least 3 other places. But as far as I can tell there is absolutely no way to wipe Mojave off the internal drive with DU. I would assume there is no way to do it with terminal either, though I haven't tried that.

It's working, its a pain in the ass, but it is working for now. Unless I can get something else to work, then I am okay dealing with this until the next beta comes out, which I would hope would allow me to downgrade, or at least fix my printer problem.

 

[Marcopolo53]

using the same process ( boot from USB Installation HS ) DU internal but Unmount Internal HD containing the Four APFS containers , choose the internal HD - the one with Apple name, and try Formatting the Entire Internal Drive

 

[Fishrrman]

bradley wrote:
"I was wanting to just do a completely fresh reinstall of High Sierra, and I am not worried about a backup with CCC because I have everything I need backed up in at least 3 other places. But as far as I can tell there is absolutely no way to wipe Mojave off the internal drive with DU."

You are wrong.
You can downgrade back to any version of the OS you wish.*
(* = that will boot and run the Mac you have)

But... there's "a catch".

The catch is:
You have to KNOW WHAT TO DO.
And so far... you're not doing it right.

 

[bradley8795]

using the same process ( boot from USB Installation HS ) DU internal but Unmount Internal HD containing the Four APFS containers , choose the internal HD - the one with Apple name, and try Formatting the Entire Internal Drive

You sir are awesome. Not sure why I didn't think of the containers before. Though your solution didn't work perfectly I changed it a bit and got it to work. Basically I deleted the container, and drive through terminal. Because DU still would not do it. That gave me the ability to format the drive, and reinstall High Sierra. But now I have 2 drives. The regular Macintosh HD, and a secondary untitled drive. The untitled drive the PCI Express drive at 27.55GB. I am assuming that the the SSD portion of my Fusion Drive.

This is my first Mac with a Fusion Drive. Should I have installed the OS on the PCI-E drive? If so, can I now just use CCC to clone the working drive to the PCI-E drive, or would a new wipe and reinstall be necessary?

[doublepost=1533827017][/doublepost]

bradley wrote:
"I was wanting to just do a completely fresh reinstall of High Sierra, and I am not worried about a backup with CCC because I have everything I need backed up in at least 3 other places. But as far as I can tell there is absolutely no way to wipe Mojave off the internal drive with DU."

You are wrong.
You can downgrade back to any version of the OS you wish.*
(* = that will boot and run the Mac you have)

But... there's "a catch".

The catch is:
You have to KNOW WHAT TO DO.
And so far... you're not doing it right.

Well thanks for the awesome insight. Care to take a look at the above post and tell me what I am doing wrong? Or at least point me in the right direction?
[doublepost=1533829762][/doublepost]And of course 60 seconds in google and I found the answers I needed about the fusion drive. Thanks @Marcopolo53 for all your help.

 

[Marcopolo53]

Bradley,
you are very welcome, glad to be of some help

 

[Fishrrman]

"That gave me the ability to format the drive, and reinstall High Sierra. But now I have 2 drives. The regular Macintosh HD, and a secondary untitled drive. The untitled drive the PCI Express drive at 27.55GB. I am assuming that the the SSD portion of my Fusion Drive.
This is my first Mac with a Fusion Drive. Should I have installed the OS on the PCI-E drive? If so, can I now just use CCC to clone the working drive to the PCI-E drive, or would a new wipe and reinstall be necessary?"

If you have a 1tb fusion drive, the SSD portion is too small (as you indicated above) to really put the OS onto. It might work as a standalone boot drive for a while, but I'm thinking it would quickly "fill up" and then wouldn't run properly.

I'll give you my advice on what to do:
1. Use either CarbonCopyCloner or SuperDuper (both are free to download and use for 30 days) to create a fully bootable clone of your current "working High Sierra OS" onto an external drive.
2. Boot from the cloned drive. NOW YOU HAVE COMPLETE CONTROL over the iMac's two internal drives, and can do anything you want with them (because you are booted from a totally-separate drive and OS).
3. Use either Disk Utility or terminal to erase both drives individually, to "Mac os extended with journaling enabled". I would run DU's "repair disk" function on each, as well.
4. Next, use terminal to "RE-fuse" the drives back into a fusion drive. (remember that HS does not use APFS for fusion drives, it uses HFS+)
5. With that done, open CCC (or SD) and "RE-clone" the contents of your external drive BACK TO the newly-created fusion drive.
6. That should do it. Reboot to the internal fusion drive and be sure to re-designate it as the startup disk in the startup disk preference pane.