I installed Centrify and joined an Active Directory domain but now it just stays on the bootup screen. I'm using Loki.
I'm unsure how I can reach a recovery console.
There is a recovery mode on elementary Loki as with Ubuntu. The GRUB menu is just hidden during startup.
Press the Esc key before elementary starts to show the GRUB menu and select "Advanced Options". From there, you can select the recovery console with the kernel you wanted.
If all else fails, it wouldn't hurt to use a recovery disk to boot into to further diagnose your problems.