My MacBook Pro early 2011 developed the same problem many people have: it stopped starting up. Trying to follow the instructions in this post: GPU problem - Boot Hangs on Grey Screen and partly this: Single-User-Recovery-Mode on High Sierra 10.13.6, especially Luca Bonavita's suggestion, I got stuck when I tried to create the Extensions-off folder. My MBP has a partitioned hard drive. When I start up in single user mode, it addresses the "first" partition, which runs on Mountain Lion, so the Extensions-off folder was created on that partition. However, ML does not not have the offending AMDRadeonX3000.kext file, so I ended up with: No such file or directory when trying to move the kext. I tried to access the other partition that runs El Capitan via target mode with the below code, but could not even get past the first step.
(Yosemite being the partition that runs El Capitan)
mkdir -p /Yosemite/System/Library/Extensions-off
I assume the
csrutil disable command is necessary afterall? If so, how can I use that on the second partition? Or is it the
/sbin/mount -uw /that was missing? Or did I just make a mistake in the code (basically just copying and pasting, as the noobe that I am...)?
Edit: The code was wrong; it should've started with
sudo and then
sudo mkdir -p /Volumes/Yosemite/System/Library/Extensions-off
The System integrity is OFF on the ML (first) partition. Edit: Apparently, ML does not have SIP, hence DiskUtility on the iMac showed OFF for that volume.
I followed the instructions for Sierra, because I was not able to boot into single user recovery mode.