[SOLVED] kdm causes Can't connect to X11 window server using ':0' as the value of the DISPLAY

mattca · 11-18-2013, 12:46 PM

Hi all, normally I boot to the console, then "startx". I'm trying out kdm, and it seems to cause a java project I need for work to fail to load.

I get this error:
"Can't connect to X11 window server using ':0' as the value of the DISPLAY variable"

When I don't use kdm, the DISPLAY variable is set to ':0.0', and I've successfully forced to be this by putting a setenv command in ~/.kde/env, but it still fails with this error.

I'm not familiar with kdm at all, how can I configure it to allow this project to run?

Thanks!

aocab · 11-19-2013, 10:40 PM

I could be way off base but I wonder if the issue is becasue kdm is using the "--no-listen tcp" option when it starts X?
As far as I know, starting X from the command line using startx does not use this option unless you include it.

You could try running "xhost +localhost" before running the java project to see if that helps.
This command will allow localhost to make connections to the X server.

See the man page for xhost for more info.
Hope this helps.

mattca · 11-21-2013, 03:08 PM

Thanks for the suggestion, aocab, I'll try that ASAP. I've got everything set up and working with ratpoison right now (including my DisplayLink monitor!), so I'll probably wait until EOD tomorrow to test it out.

mattca · 11-22-2013, 04:15 PM

Alright, so I seemed to have found a workaround. You were on the right track, aocab. I need to run this project as root, and it turns out that root can't connect to the X server. Running xhost as a user worked as expected, but doing it as root produced the same error I was getting when trying to run the project.

A google search led me to this thread:
http://www.linuxquestions.org/questi...s-root-314573/

Most of the suggestions there didn't help much, but doing this:

Code:

ssh -X -l root localhost

instead of "su" allows it to work.

So! The question now is, how can I make this work without a workaround? I tried commenting out this line:

Code:

ServerArgsLocal=-nolisten tcp

in /etc/kde/kdm/kdmrc but it didn't help.

Any suggestions?

Thanks!

aocab · 11-22-2013, 06:23 PM

I would think that you could use something similar to what Alien Bob does when he builds a Linux Kernel from scratch.

Code:

echo $DISPLAY                  # you'll be needing this value 3 lines below
sudo -i                        # or "su -" on older Slackwares
xauth merge ~alien/.Xauthority # use your own username here instead of "alien"
export DISPLAY=:0.0            # use the value of DISPLAY you've seen 3 lines before

See the first section here about X and su:
http://alien.slackbook.org/dokuwiki/...kernelbuilding

Hope this helps...

mattca · 11-29-2013, 04:42 PM

I found a solution - turns out "kdesu" is the proper way to run X applications with root privileges within KDE.

Thanks for the help!

ReaperX7 · 11-29-2013, 08:54 PM

kdesu will act as a sudo like layer, but even I've had problems with it working correctly.

There is an option in kdmrc to allow root login, which I suggest you enable.

mattca · 12-02-2013, 12:24 PM

Quote:

Originally Posted by ReaperX7

kdesu will act as a sudo like layer, but even I've had problems with it working correctly.

There is an option in kdmrc to allow root login, which I suggest you enable.

AllowRootLogin is already set to "true" in /etc/kde/kdm/kdmrc...