downgrading Mojave 2018 touchbar Macbook Pros to High Sierra (Secure Boot)

New Contributor

Hi All!

In our environment, we still have some dependencies on High Sierra because there are some software titles that are not compatible with Mojave at this point.

We have been able to roll back touchbar Macbook Pros to High Sierra using a base OS created with Auto DMG. We do this with disk utility over thunderbolt, however after restoring the APFS image due to Secure Boot it will boot into internet recovery once to "verify startup disk" then it will restart and boot into internet recovery again to run an update and I assume "bless" the startup disk. After that everything works great, but there are times when it takes a long time to get to internet recovery even with our "amazing" internet connection on campus (956Mbps down 862Mbps up as of now). Sometimes it will take an hour to do this and other times it will take 15 minutes, which is frustrating when we can blast a base OS to a 2017 MacBook Air and be ready in 2 minutes.

I just wanted to write this up to see if anyone else is running into this same issue and has any input? Thank you!


Valued Contributor II

To my knowledge you can't Apple bakes in all the drivers with the OS release. If the originally didn't originally ship with 10.13 then it's likely that you wouldn't be able to install it.

Honored Contributor II

@jwojda For the 2018 MacBook Pros that didn't include the optional Radeon Pro Vega GPU downgrading to High Sierra 10.13.6 was possible, you just had to get the right build with the script. I'm not sure the same applies to the recent MacBook Pro refresh, and I'm not curious enough to try and find out.

@dgasin01 It certainly won't be as fast as dumping the AutoDMG created image via Thunderbolt, but have you considered using the --eraseinstall option for the startosinstall tool in the Mojave and High Sierra installers to wipe a MacBook Pro that came with Mojave and install High Sierra? We had to do an intermediate downgrade to Mojave 10.14.0 for machines that came with 10.14.1 or 10.14.2, but I'm not sure if that's still required (having finally cleared the hurdles to deploying Mojave I'm not inclined to try)

Contributor III

If you downgrade Apple may not support as potentially you void the warranty.