[Linux]TigerVNC failed on start

Symptom:
After a power outage, my CentOS 7 server restarts. When using systemctl start vncserver@.service, error occurs

HOWTO fix it:
- issue journctl -xn, and look for some clue. In my case, there is a hint saying something like “deleting /tmp/.X11….. if the xserver is not in use”
- issue rm -rf /tmp/.X11