XQuartz El Capitan not setting $DISPLAY for a Vagrant built VM I've built multiple VMs with Vagrant (CentOS, ArchLinux, Debian), all exhibit the same problem:

When I ssh onto the VM, 

0;vagrant@archlinux: ~vagrant@archlinux:~$ echo $DISPLAY

0;vagrant@archlinux: ~vagrant@archlinux:~$ 


I've tried troubleshooting as explained here: http://www.xquartz.org/Support.html, but that didn't help.

I'm running El Capitan 10.11.3, XQuartz 2.7.8.

All I'm trying to do is to run vagrant ssh -c 'xclock' and have a window show up on my host OS.
I had this same issue but realized I never restarted OS X after installing XQuartz. Once I rebooted, XQuartz was correctly detected and X11 forwarding worked.