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10.7: Restore Apple Hardware Test boot mode
Authored by: alexiskai on Aug 25, '11 12:27:13PM

I'm pretty sure this doesn't work if your boot volume is encrypted. You'd need to create a separate unencrypted boot disk/partition, boot to that, install AHT, then boot into AHT.

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10.7: Restore Apple Hardware Test boot mode
Authored by: Crazor on Aug 28, '11 05:24:14AM

On encrypted systems, there is a small booter partition which contains the EFI application that asks for your password, loads the kernel from the booter partition and once the kernel found and unlocked your encrypted volume, system startup continues as usual.

If your system has the recovery system (and most Lion installs should have), it and the booter share a partition after your root volume. diskutil list will confirm there is this hidden partition called "Recovery HD". If your system for some reason does not have the recovery system, but you encrypted the root volume, the partition will be named "Boot OS X".

Either way, just mount this hidden partition ("diskutil mount Recovery\ HD" or "diskutil mount Boot\ OS\ X") and then copy the .diagnostics folder to /Volumes/{Recovery\ HD|Boot\ OS\ X}/System/Library/CoreServices.

After that, you can boot to AHT by holding D, like on unencrypted systems.

It is probably a good idea to copy AHT to the Recovery HD, regardless of the encryption status of your root volume, but I haven't tested if the firmware finds AHT there when the partition is not the first HFS+ volume on your primary disk.

Curiously, one can boot the recovery system, but not AHT, when the firmware password is set...

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10.7: Restore Apple Hardware Test boot mode
Authored by: jollyroger on Jan 20, '12 06:42:08AM

I just tried doing this, but there isn't enough space on the recovery volume to copy all of the files in the .diagnostics folder. : (


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