How do I get 2560x1440 resolution within VirtualBox on a Mac?
Solution 1:
Well this is embarrassing.
It turns out that all I needed to do was run in full screen mode and then Ubuntu will figure out the new resolution automatically. I could have sworn I tried that. Oh well.
Don't know how to "cancel" this question, I'm afraid.
Solution 2:
This question has already been answered, however, I'd like to share the following post worked for me, namely commands I used were:
xrandr --newmode "2560x1440_60.00" 311.83 2560 2744 3024 3488 1440 1441 1444 1490 -HSync +Vsync
xrandr --addmode Virtual1 2560x1440_60.00