Sep 23, 2021 'Reinstall Mojave: Recently installed Big Sur on my 2014 MBP but doesn't play well with some of my apps. Tried to reinstall Mojave but downloader would not install stating that I have the most recent OS. Can't use Time Machine as this is on an external drive which won't open in Big Sur. Anybody know a workaround?' -Verify Compatibility. I’m trying to get Mojave to install and I’ve gone through all the steps to: 1. Create install USB disk for Mojave 2. Boot from Mojave install disk 3. Delete internal SSD 4. Install Mac OS here, it only gives me a choice to “Reinstall macOS” and goes out and tries to grab Catalina. It doesn’t use the install files on the USB to.

  1. Reinstalling Mojave On Mac
  2. Reinstalling Mojave
  3. Reinstalling Os Mojave
  4. Reinstalling Mac Os Mojave
Catalina

UPDATE: This method does not work on macOS Big Sur. It can only be used on Catalina and older

Reinstalling Mojave On Mac

When a freshly built or rebuilt Mac gets to the “country choice” screen as part of Setup Assistant, and is connected to a network, the device checks in with Apple to see if it is assigned to be enrolled to an MDM service using Automated Device Enrollment (what we used to call DEP). If you forget to assign the device to the correct MDM service before getting to this point, it can be difficult to get it to enroll to the service you intended without reinstalling the OS once again.

In recent times, the following command, which is supposed to reset the DEP cache, has become more reliable:

The question is, how to run this command during the Setup Assistant process? You can bring up Terminal during Setup Assistant, but since there is no admin account on the device up to the point when Device Enrollment takes place, one cannot run the above command.

Gaining root access at the Setup Assistant

To be able to run the above command, we need to gain root access. I learned this is possible from @yohan via MacAdmins Slack.

First, we need to re-enable the Language Chooser Screen, which is the first screen in Setup Assistant but is not shown by default on computers more than once. To do this, we can do one of two things:

Enabling the Language Chooser screen on Macs without a T2 chip

Boot into Single User Mode using Cmd-S.

  1. On a Mac running Catalina or greater, run the following commands:

  2. On a Mac running Mojave or earlier, run the following commands, replacing the volume name if your system volume is not named Macintosh HD:

Upon restarting, you should see the “language chooser” screen.

Enabling the Language Chooser screen on Macs with a T2 chip

Single User Mode is not available on T2 Macs, so instead, boot into Recovery Mode using Cmd-R and open Utilities > Terminal (you can also do this on non-T2 Macs if you wish). Then, run the following commands:

Now, quit Terminal, and reboot back into the system volume, and you should see the “language chooser” screen.

Opening Terminal as root on the Language Chooser screen

To open Terminal at this screen, click Ctrl-Alt-Cmd-T (all keys pressed together). Terminal at this point is running as root. So, now you can run:

Then close Terminal and continue with Setup Assistant as normal. In my recent experience this has always been successful in resetting the DEP cache so that it will check in with Apple again and get the correct current DEP status.

Reinstalling Mojave

June 8, 2019

Today I performed a clean install of macOS Mojave 10.14 on the fusiondrive of my Mac Mini 2014. Below I have written down my notes.

Reinstalling Os Mojave

Downloading MacOS Mojave from the App Store

Get macOS Mojavein the App store. The download is just over 6GB. When the installerstarts, quit the installer. The installer will remain in theApplications folder.

Creating the USB installer

Insert a USB stick of at least 8GB. Launch Disk Utilities, select thethumb drive in the left pane and select Erase.

Name the stick 'Untitled', select 'OS X Extendend (Journaled)' as theformat and 'GUID Partition Map' as the scheme and click the Erasebutton. When finished, click Done and close Disk Utility.

Launch Terminal and paste the following two lines:

This will erase the thumb drive and copy the installer:

Install macOS Mojave 10.14

Restart your Mac and hold down the Option key as soon as you hear thestart up sound. Use the keyboard arrows to select 'Install macOSMojave'. After a short while a window is shown. Select the 'DiskUtility' option.

Select the fusion drive of your Mac, in my case 'Macintosh HD', andselect Erase. I choose APFS for the format.

Reinstalling Mac Os Mojave

When done, return to the macOS Utilities screen and select 'InstallmacOS'.