Mojave USB installer problem

[hellfried]

I am using a 2019 13" MBP running Catalina. I am trying to install Mojave on an external SSD drive. I downloaded the full installer for Mojave from App Store and created a bootable USB installer with it. I can boot into it at startup but it takes me straight to MacOS Recovery. It will only allow me to install Catalina on the SSD drive. No option for Mojave. Help!

 

[Snow Tiger]

I am using a 2019 13" MBP running Catalina. I am trying to install Mojave on an external SSD drive. I downloaded the full installer for Mojave from App Store and created a bootable USB installer with it. I can boot into it at startup but it takes me straight to MacOS Recovery. It will only allow me to install Catalina on the SSD drive. No option for Mojave. Help!

This is not the Mac Book Pro forum , shoo !

You are not permitted by Apple to load earlier versions of macOS on drives than the macOS of the Mac you are currently using , even for another drive .

OK , I thought of a solution . Using Start Up Manager , by pressing option key at start up , choose the USB OS installer icon and boot from that . Once the installer permits , choose your external drive to install Mojave onto .

Your installer must have Mojave version 10.14.5 or later .

 

[tsialex]

You are not permitted by Apple to load earlier versions of macOS on drives than the macOS of the Mac you are currently using , even for another drive .

Not correct.

You can go back to the earliest version that your Mac supports. With 2019 13"MacBook Pro, is macOS 10.14.5 (18F2058).

The current Mojave Mac App Store installer, 10.14.6, will install just fine with 2019 13"MacBook Pro.

A lot of people buying the refresh 2018 Mac mini, what is being erroneous called 2020 Mac mini, that Apple delivers with Catalina can install Mojave just fine.

 

[Snow Tiger]

Not correct.

You can go back to the earliest version that your Mac supports. With 2019 13"MacBook Pro, is macOS 10.14.5 (18F2058).

View attachment 910109

The current Mojave Mac App Store installer, 10.14.6, will install just fine with 2019 13"MacBook Pro.

A lot of people buying the refresh 2018 Mac mini, what is being erroneous called 2020 Mac mini, that Apple delivers with Catalina can install Mojave just fine.

OK , then maybe the issue the OP is having is that he is using a Mojave installer with a version that predates 10.14.5 .

He should build another installer with the latest version of Mojave .

 

[tsialex]

OK , then maybe the issue the OP is having is that he is using a Mojave installer with a version that predates 10.14.5 .

He should build another installer with the latest version of Mojave .

No, it's probably T2 Security Settings.

Mac App Store only sends you the current version. To get 10.14.5 (normal build don't support just released Macs, 2019 MacBook Pro had a different release of 10.14.5, 18F2058, than everyone else, 18F132) or earlier, he would had to download it before July 22 2019.

About Startup Security Utility on a Mac with the Apple T2 Security Chip - Apple Support

Use Startup Security Utility to make sure that your Mac always starts up from your designated startup disk, and always from a legitimate, trusted operating system.

support.apple.com

 

[Snow Tiger]

Not correct.
You can go back to the earliest version that your Mac supports.

My statement is correct , if someone is trying to install an older OS version onto an external drive from a Mac OS session running a newer version of macOS .

He is not using Start Up Manager to boot the installer from .

He must also have chosen the USB boot installer from the Start Up Disk selector within System Preferences and something went wrong - a redirect of sorts .

[automerge]1588086042[/automerge]

No, it's probably T2 Security Settings.

Mac App Store only sends you the current version. To get 10.14.5 (normal build don't support just released Macs, 2019 MacBook Pro had a different release of 10.14.5, 18F2058, than everyone else, 18F132) or earlier, he would had to download it before July 22 2019.

About Startup Security Utility on a Mac with the Apple T2 Security Chip - Apple Support

Use Startup Security Utility to make sure that your Mac always starts up from your designated startup disk, and always from a legitimate, trusted operating system.

support.apple.com

I was thinking he was using an older installer .

Does Apple permit the installation of an OS onto an external drive the security settings do not permit to be used as a start up device ? That would seem weird . I would think there would be some sort of check on that , before installation .

 

[tsialex]

Alex , are you certain he can do that from a macOS session ?

I think what the OP is attempting is to click on a Mojave installer icon on the desktop of a Mac running Catalina , to install Mojave on an external drive . Is this permitted ?

He is not using Start Up Manager to boot the installer from .
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I was thinking he was using an older installer .

Does Apple permit the installation of an OS onto an external drive the security settings do not permit to be used as a start up device ? That would seem weird . I would think there would be some sort of check on that , before installation .

Only way to downgrade is via createinstallmedia USB installer. You can install if the T2 Security is disabled.

 

[tsialex]

My statement is correct , if someone is trying to install an older OS version onto an external drive from a Mac OS session running a newer version of macOS .

Sure, it's correct, but it's not the only way to install macOS.

Does Apple permit the installation of an OS onto an external drive the security settings do not permit to be used as a start up device ? That would seem weird . I would think there would be some sort of check on that , before installation .

You can install if the T2 Security is disabled and external boot enabled.

 

[hellfried]

Thanks for all the comments and tips. I think its the T2 chip. I can boot into the usb installer using my 2017 Macbook Air and it correctly gives me the option of installing Mojave on my SSD.

@tsialex How does one disable the T2 chip and is it advisable to do so?

 

[tsialex]

I already linked to the Apple Support article, post #5. Read it to see how to disable SecureBoot and enable external booting.

About Startup Security Utility on a Mac with the Apple T2 Security Chip - Apple Support

Use Startup Security Utility to make sure that your Mac always starts up from your designated startup disk, and always from a legitimate, trusted operating system.

support.apple.com

 

[Fishrrman]

OP wrote:
"How does one disable the T2 chip and is it advisable to do so?"

Yes.
I would advise you to disable it (one of the very first things I did on my 2018 Mini, and a year later, it still runs just fine).

Do this:
1. Boot to the recovery partition (command-R at boot).
2. When you get there, open the startup security utility
3. DISABLE it (as much as it can be disabled) by choosing "the lowest options" in each panel
- "no security" and "allow booting from external media"
4. Close startup security and reboot to your regular drive at least once.

NOW try connecting your external bootable drive or installer, and try again.