You need to load installation UI as user2.
Try to following this:
Login as root:
sudo su Test the x server:
xclock If you can see a clock running, that's good to go, now try run this:
xhost The result should like this:
xhost SI:localuser:tri # tri is my user name Now let user2 access xhost
xhost +SI:localuser:user2 now try to login again to user2 and try to open any of GUI program.