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

I know this is not a rare problem. I've read the threads here regarding this for the most part and the advice I have picked up hasn't helped. I often get this message when trying to run apps in KDE as root:

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

I have tried xhost + and xhost + localhost and it doesn't seem to do anything. Of course, if I log in as root rather than just su to root I don't have this problem. So it is obviously a permissions issue. Does anybody know how to fix this? I haven't had this problem until I had to reinstall recently. Suggestions most appreciated.

BTW I run Debian. Thank you again.

There's a couple things you need to do. First become root and from a command prompt. Type:

root@yourhost#>echo $DISPLAY

If you don't get :0.0 for output, we need to make it that way. So type

root@yourhost#>export DISPLAY=:0

That takes care of the first part. Now I assume you are logging into the box with your user account, starting x if it's not already started, then su -ing to root. If this is the case, you need the MIT Magic Cookie!

Run these commands substituting your non-root username for 'user'.

root@yourhost:~>cd /root/ (in case you weren't there)
root@yourhost:~>xauth -f /home/user/.Xauthority extract ./xcookie :0.0
(if the above command complains that :0.0 isn't found, try it again with :0 or 0:0, most likely :0.0 will work though)
root@yourhost~>xauth merge ./xcookie

What you just did is pulled a copy of the MIT-Magic-cookie thing from your user account's Xauthority and put it in yours.

I just wanted to say thank you. Your directions worked flawlessly. I saw that you replied previously and just tried it out today. Thanks again :D

wouldn't this be easier?

xhost +localhost
su
<enter root password>
execute whatever app
exit
xhost -localhost (optional)

OR, just add xhost +localhost to whatever startup script runs when you load your X environment...

Hi Hayl. Thank you for your reply as well. I later found that the previous method while effective, is only temprorary. Once I shutdown X I had to issue the command again (although still appreciative for the suggestion).

So I tried the method you had described and it did not work for me at all. I have seen the method you have described offered as advice several times...but it never works for me. I don't know why:

me@Debian:~$ xhost +localhost
localhost being added to access control list
me@Debian:~$ su
Password:
Debian:/home/me# synaptic
Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified

What am I doing wrong here?

Hi
While trying the above one I got error like this


xauth: error in locking authority file /home/user/.Xauthority


Thank you

I am trying to connect the Cygwin X on Window 7 machine through putty; However I am getting the below error message:

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

Error: Can't open display: 151.149.171.82:0

Below are the steps I followed:

1. Launch the 64 bit Cygwin X.
2. It starts the Cygwin X and shows its symbol on right corner.
3. Then I started the xterm and start the xclock which is required to start the Xmenu through putty.
4. After that I have used the below commands to access the X display windows:
export DISPLAY=IPaddress:0.0
xhost +
5. Here I am getting that error. I am not able to open the required screen as well.
6. I tried to add the IP in host file but still getting the same error.
7. I have also tried xauth list $DISPLAY but it didn't show me the display list

Can you please help me out to get the solution of this so that I can use the cygwinX on Window 7?