Cannot boot from a MacOS Pro

[cparada]

I have no way to boot from my Mac Pro.

I already tried to do a few things describing in some threads, like change policy, but the option to enable booting from external devices is not there.

Any clue, or confirmation that it does not work?

[PetrCihlar]

What are you trying to boot? Remote exam USB stick?
Mac Pro can certainly boot from an external USB device. Make sure the Secure Boot is disabled in the Apple startup security utility
https://support.apple.com/en-us/HT208198
Personally, I would not attempt using Mac Pro for the exam as I believe there will be compatibility issues. Let us know if you made it to the compatibility test.

[cparada]

Yes, I am trying to boot from an exam USB stick. I created the USB image using the provided iso and the dd command in https://www.redhat.com/rhdc/managed-files/tr-remote-exams-preparation-ebook-f27382-202103-en_2.pdf.

However, booting from USB using Option key is not working. Holding the start buttom drives me to the boot policies setting, but the Allowed Boot Media option is not there as described in https://support.apple.com/en-us/HT208198. Not sure if this is because the MacBook hw/sw version or because any RH policy on it.

Anyone has any solution? other than not using the Mac for the exam, which is the option otherwise

[PetrCihlar]

did you create the USB stick correctly? There is an error in the pdf manual, describing the use of dd command for Mac. The home folder is not "home" but "Users". So you need to modify the path. Did you press and hold the ALT key correctly? The USB stick should surely be recognized and visible if it contains a valid bootable system.
Also, do not use any USB-C multiport adapter to connect the USB-A type USB stick. Those adapters do not work often.

[cparada]

I did everything as you correctly, but no success. Mac does not enter in the mode to select which boot drive to use.

Wrt USB-C multi-adapter it is a must, as my laptop does not have a USB port. Maybe this this the issue.

I'll try with a Windows machine now.

[PetrCihlar]

no way you cannot open the boot menu on Mac by pressing and holding down the Option key just after the start-up chime. The only reason may be non-Apple compatible keyboard. Check this out. Regards Petr

[BrianStinehart]

Hello,

I'm having a similar issue, but I am able to access the correct Startup Security Utility settings, which have been set to "No Security" and "Allow booting from external or removable media." Even with these settings applied, I'm still not able to see the external startup disk in Startup Manager.

As instructed, I created the USB image using the provided iso and dd command, and I am using a direct, single port USB-C adapter to connect the USB-A type stick. 

Any ideas? I have an exam in 20 minutes and have been trying to resolve this for days

[BrianStinehart]

Have also tried an older ISO with no joy: https://static.redhat.com/downloads/training-certification/rhrexboot-2020-08.iso

[Tess]

Sad news, but if the laptop didn't work yesterday, you should have moved your exam 24h before the deadline. Now you're gonna lose your timeslot and money.

[Tess]

https://www.redhat.com/rhdc/managed-files/tr-remote-exams-preparation-ebook-f27382-202103-en_2.pdf 

Page 37

The manual from RedHat very explicitly says that:

1. The exam environment ISO is not compatible with Apple ARM-based systems.
2. The exam environment ISO is not compatible with Apple x86-based systems that have the T2 security chip.
3. The exam environment ISO is compatible in a limited degree with Apple x86-based systems from 2017 and earlier. Nothing else.

A Mac is not a safe bet for a Red Hat exam, unfortunately. I'm lucky enough to have a throw-away Windows laptop at home, just for this stuff.