Can't install mac os on external drive

[jamesfarrell70]

man, everything I read is wrong. My current os, which is 12.7.1 monterey is too old to install mojave on external SSD drive USB.
I tried copying the mojave installer to the drive, restart with option key and it immediately goes into internet recovery. I can't install the OS when booted as I get the "OS too old error"

Any ideas to make this work? None of the startup options work, always goes to internet recovery

 

[Nermal]

I tried copying the mojave installer to the drive

How did you do this? Did you use the createinstallmedia tool (or something that "wraps" it) or did you just drag and drop the .app onto the drive? The former will work, the latter won't.

 

[jamesfarrell70]

I dragged the mojave install file to the USB drive and launched it from there.

 

[jamesfarrell70]

I can see this is going to take hours and hours.
Kevin@Kevin-MBP Mojave % pwd

/volumes/Mojave

Kevin@Kevin-MBP Mojave % sudo /Applications/Install\ macOS\ Mojave.app/Contents/Resources/createinstallmedia --volume /volumes/Mojave

Password:

To use this tool, you must download the macOS installer application on a Mac with 10.12.5 or later, or El Capitan 10.11.6. For more information, please see the following: https://support.apple.com/kb/HT201372.

Kevin@Kevin-MBP Mojave %

Volume/Mojave is my external drive

 

[jamesfarrell70]

PRogress

Last login: Wed Dec 6 17:10:48 on ttys000

Kevin@Kevin-MBP ~ % sudo /Applications/Install\ macOS\ Mojave.app/Contents/Resources/createinstallmedia --volume /volumes/123

Password:

Ready to start.

To continue we need to erase the volume at /volumes/123.

If you wish to continue type (Y) then press return: Y

Erasing disk: 0%... 10%... 20%... 30%... 100%

Copying to disk: 0%... 10%...

 

[jamesfarrell70]

SAme error it created the media on the USB drive but went to install it and OS is too old error again

 

[jamesfarrell70]

Got it installing. After I'm done, how to I switch between the OS on the external drive and my current OS on the internal drive?

 

[Nermal]

I'm glad you got it installing. It's never as easy as it should be, apparently!

You can choose a boot volume by holding Option at the boot chime.