How to Fix "Xlib: No protocol specified"

While installing Oracle database I was getting this error. I searched various blogs and forums and
found out many solutions but lastly I got one solution which worked for me.

But well I will post all the possible ways which you can try (as per my knowledge) to overcome this issue.


Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified

Specify the display protocol by logging into the user account you are getting the error

Solution 1:
$ export DISPLAY=localhost:0.0
$ xhost +

Solution 2:

$ export DISPLAY=(machine_name):0.0
For example:
$ export DISPLAY=
$ xhost +

Solution 3 (which worked for me)
Login to the user account where you are getting the above error

$ xauth $DISPLAY
xauth: creating  new authority file /home/oracle/.Xauthority
xauth: (argv):1: unknown command ":0.0"

The best way to check whether your Xlib display protocol is working or not is by using xclock command

$ xclock
After running this command you should see a small clock on your screen.

Solution 4
In case the above solution does not works
Login as root

# xauth $DISPLAY
xauth: creating new authority file /home/root/.Xauthority
# xauth list $DISPLAY MIT-MAGIC-COOKIE-1 f601e6a29ea688786765434c5c6325071
Now copy the above output and su to the user you are facing issue
# su - oracle
$ xauth add MIT-MAGIC-COOKIE-1 f601e6a29ea688786765434c5c6325071
xauth: creating new authority file /home/oracle/.Xauthority

Now test if your DISPLAY is working

You should get a small clock output on the screen