Troubleshoot Refused VNC Connection in CentOS 7

Troubleshoot Refused VNC Connection in CentOS 7

Posted on March 15, 2015 by Istvan Szarka — 2 Comments

The other day I connected to my CentOS 7 computer from Windows via RealVNC Viewer. Everything went fine, but after I left the machines unattended for a short time, the connection froze to the point that I had to shut CentOS down and boot it again. When I tried to connect again, I got an error message saying something like “The connection was refused by the host computer” or similar, I can’t remember exactly. I rebooted CentOS several times, but nothing changed. Now I had to connect a monitor and the necessary peripherals to the box and start troubleshooting.

First, I checked the status of the VNC service:

[root@localhost Desktop]# systemctl status vncserver@:2.service -l
vncserver@:2.service - Remote desktop service (VNC)
   Loaded: loaded (/etc/systemd/system/vncserver@:2.service; enabled)
   Active: failed (Result: exit-code) since Sat 2015-02-28 14:37:00 CET; 10min ago

Feb 28 14:37:00 localhost.localdomain systemd[1]: vncserver@:2.service: control process exited, code=exited status=2
Feb 28 14:37:00 localhost.localdomain systemd[1]: Failed to start Remote desktop service (VNC).
Feb 28 14:37:00 localhost.localdomain systemd[1]: Unit vncserver@:2.service entered failed state.

The VNC service apparently failed to start. If you don’t know why I used vncserver@:2.service, please read my earlier post about configuring VNC. I tried to start the service, but it kept failing:

[root@localhost Desktop]# systemctl start vncserver@:2.service
Job for vncserver@:2.service failed. See 'systemctl status vncserver@:2.service' and 'journalctl -xn' for details.

As I was digging through the internet, I found some clues about corrupted session files that had to be deleted to solve this problem. The files were supposed to be in the /tmp/.X11-unix directory (capital X11, Linux is case-sensitive!). When I checked the contents of /tmp, I found this:

There was no /.X11-unix directory inside. The issue was, that this folder is hidden and such items can only be seen if you put -la after ls, like this:

Now I saw the folder I was looking for at the end of the list. Inside /.X11-unix were the session files:

The corrupted file belonging to “vncuser”, the user I configured for VNC access, was X2. I removed it with the rm /tmp/.X11-unix/X2 command. Then, I started the service, rebooted the computer and I was able to seamlessly connect to my CentOS machine through VNC.