I have attempted to follow this guide:
It seems to have gotten partway through the boot process.
From OSX, the list of partitions on the boot device (I apologise for some serious potatocam):
Grub options after pressing 'edit' are here:
Initramfs prompt appears as follows:
The walkthrough suggests removing the internal hard disk of the laptop to do this procedure, but that is NOT an option for me. I only need to boot into this environment once, to perform an installation.
Further info - using OSX's diskinfo, I see the following UUIDs:
/dev/disk2s1 - C972F4B3-83FF-4E9F-A9CC-A7F0FDF6477D /dev/disk2s2 - 44980794-0CC8-48FF-A1A4-902C6A781B7F /dev/disk2s3 - BBFAD016-C4C4-4A70-9A44-4ED03CFB27B7 /dev/disk2s4 - D71A4E6A-014F-4F24-B54B-B3E70C5E753B
I think the largest partition, /dev/disk2s3, should probably be considered root? But changing the grub config to BBFA... does not help - the kernel cannot find that device. Also, it doesn't even load any partitions in /dev/sdb, only /dev/sdb itself.