Let says you try to access to GUI as user2 (normal user), then 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.

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.

You need to load installation UI as user2.

Login as root:

sudo su

Test the x server:

xclock

If you see a clock running you are good to go. Now run

xhost

Result should be

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.

Let says you try to access to GUI as user2 (normal user), then 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.