Try these steps for Redhat and best of luck.
- Review ~home/.vnc/xstartup file and you may have to uncomment first couple of lines to enable VNC Session manager
- Start VNC by executing /usr/bin/vncserver command . For the first time, you need to setup a password to protect your VNC Session.
"ps -la" will list all user processes and you can find VNC processes and kill it using "kill -9 <VNC Process ID>"
Cleaning up VNC Files