Well, like the title says, I have inittab set to id:5:initdefault but it always boots to runlevel 3 (as confirmed by "runlevel" and "who -r")
Typing 'init 5' brings the GUI up. Also, appending '5' to the kernel grub line also brings up the GUI.
By why is inittab ignored?
initdefault
line ininittab
exactly as you've shown? There should be colon on the end - soid:5:initdefault:
. Although if init didn't recognise the line I'd expect (from the docs) it to prompt for run level.