VNC server setup on Linux

Setting up VNC on linux is very straight forward provided we follow ALL steps.

Here are the steps to setup VNC on Redhat Linux:
1) Edit /etc/services to add VNC related information/ports
2) Edit /etc/xinetd.d/vncserver to specify which user and which ports to use to run VNC
3) Check the status of vncserver, if disabled then enable it for run level 3/4/5.
4) Invoke "gdmconfig" and enable XDMCP protocol.
5) Restart "xinetd" service. Viola! You are done setting up VNC.
6) Use any VNC viewer to connect the server on ports mentioned in /etc/xinetd.d/vncserver (in this case, it is port 5972 or 5972/ or simply port 72 or 73 for a VNC viewer).

# cat /etc/services
:
:
:
# Local services
#
# VNC Servers
#
vnc-640x480x8 5950/tcp
vnc-800x600x8 5951/tcp
vnc-1024x768x8 5952/tcp
vnc-1280x1024x8 5953/tcp
vnc-1600x1200x8 5954/tcp

vnc-640x480x16 5960/tcp
vnc-800x600x16 5961/tcp
vnc-1024x768x16 5962/tcp
vnc-1280x1024x16 5963/tcp
vnc-1600x1200x16 5964/tcp

vnc-640x480x24 5970/tcp
vnc-800x600x24 5971/tcp
vnc-1024x768x24 5972/tcp
vnc-1280x1024x24 5973/tcp
vnc-1600x1200x24 5974/tcp

vnc-640x480x32 5980/tcp
vnc-800x600x32 5981/tcp
vnc-1024x768x32 5982/tcp
vnc-1280x1024x32 5983/tcp
vnc-1600x1200x32 5984/tcp
 
# cat /etc/xinetd.d/vncserver
# description: This vnc server serves vnc-1024x768x24 VNC sessions
service vnc-1024x768x24
{
        disable         = no
        socket_type     = stream
        protocol        = tcp
        port            = 5972
        wait            = no
        user            = demo
        server          = /usr/bin/Xvnc
        server_args     = -inetd -query localhost -once -geometry 1024x768 -depth 24  -SecurityTypes=None
}
# end
# description: This vnc server serves vnc-1024x768x24 VNC sessions
service vnc-1280x1024x24
{
        disable         = no
        socket_type     = stream
        protocol        = tcp
        port            = 5973
        wait            = no
        user            = demo
        server          = /usr/bin/Xvnc
        server_args     = -inetd -query localhost -once -geometry 1280x1024 -depth 24  -SecurityTypes=None
}
# end


# chkconfig --list vncserver
vncserver      0:off1:off2:off3:on4:on5:on6:off

# /sbin/service xinetd restart
Stopping xinetd: [  OK  ]
Starting xinetd: [  OK  ]

# /usr/sbin/gdmconfig

# echo "With gdmconfig.... enabled XDMCP (from the last tab)"
With gdmconfig.... enabled XDMCP (from the last tab)

# /sbin/service xinetd restart
Stopping xinetd: [  OK  ]
Starting xinetd: [  OK  ]
# 

OPTIONAL:
Important tip:
Following section is applicable ONLY when gdmsetup gui is not available/disabled for any reason.
In this case, first take the backup of /etc/X11/gdm/gdm.conf file so that it can be restored if needed. Then edit this file for XDMCP section to look like below:

Originally, it will look like below:

[xdmcp]
Enable=false

For VNC, it should look like below (need to modify manually if gdmsetup gui is not available):
[xdmcp]
Enable=true
HonorIndirect=true
MaxPending=4
MaxPendingIndirect=4
MaxSessions=16
MaxWait=15
MaxWaitIndirect=15
DisplaysPerHost=2
PingInterval=1
Port=177
Willing=/etc/X11/gdm/Xwilling

After this change is done, restart the xinetd service as mentioned above. VNC should work now.