Sudo nvram autopower on M2 now exclamation at startup!

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Hi All,

A warning to all fellow apple silicone users: I just found my M2 air unbootable after using a recommended terminal command to disable the auto power on with lid opening feature. I entered the sudo nvram auto_boot=0 and then sudo nvram auto_boot=false (or similar) commands and at first reboot my system was toast with the exclamation mark indicating I needed to either revive or restore to firmware!

What a shame apple make this impossible to disable using sensible menu options. I'd love to try some other options to disable it but I'm just glad its now back to normal.

For any other victims: I solved it by holding down the power button for an extended time where it says its bringing up alternative startup options. I just then clicked my usual Mac HDD as the device to boot from and it was fine. A Sudo nvram -P revealed that Autoboot was now true so thankfully it seems to have corrected itself. Just as well bcos you can't clear the NVRAM or SMC on apple silicone!
 
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Your Mac's Specs
MBP 16" 2021 (M1Pro), iPhone 13 Pro, an iMac, plus ATVs, AWatch, MacMini
You changed something in the sealed volume, and on boot, the security system detected the change, hence the blocked boot. That is now how security works. I don't know who "recommended" whatever terminal command you used, but they clearly do not understand how the security has been changed.

Just as well bcos you can't clear the NVRAM or SMC on apple silicone!
Not true. SMC is reset on every cold boot automatically. So, if you want to reset SMC, just shut down the Mac and wait about 5 seconds before cold booting.

And it's Apple Silicon, not silicone.
 

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