iMac 2013 Boot to USB

Hi, I got a 2013 iMac from a friend. I decide to shrink the Mac OS partition and added Zorin.
It’s been a while and really never used the Mac OS, so finally decided I would remove that partition and expand the Zorin partition to use the whole drive.
I installed GParted and figured I could easily do that, by formatting the MacOS partition and then expanding the Zorin partition.
Problem is that when I’m booted from Zorin, it won’t let me change the size or move that partition.

OK. So, I figure I have to boot from a live USB so that the Zorin partition is no longer active.
Apparently, to boot a Mac with a USB, you have to use a USB keyboard and hold the Option key during boot. I only have a Windows USB wireless keyboard and I’ve tried holding the Windows key or the Left ALT key but no luck. Not sure how I got it to work the first time,but it’s been quite a while.

Is there any trick I’m missing?

Problem solved after reading more internet posts. The key is to wait for the startup chime before clicking and holding the Option(ALT) key. Looks like I was holding it before the chime or too long after it. There is an Apple Support post that said to hold the Option key while pushing the Power button. This must be for newer machines.
I was able to boot from USB into Zorin and then use GParted to delete the MacOS partition and then move/expand the existing Zorin partition to use the full drive. Now need to start filling up that space :slight_smile: