Problem: On CentOS 4.8, logging into VNC session on server for first time does not show Gnome session.

Solution: Edit the VNC xstartup file.

Edit the ~/.vnc/startup and replace the line

# xterm -geometry 80×24+10+10 -ls -title “$VNCDESKTOP Desktop” &

twm &

with

gnome-session &

When vncserver is first run, the xstartup file should be similar to the following:

[oracle@localhost ~]$ cat .vnc/xstartup
#!/bin/sh

# Uncomment the following two lines for normal desktop:
# unset SESSION_MANAGER
# exec /etc/X11/xinit/xinitrc

[ -x /etc/vnc/xstartup ] && exec /etc/vnc/xstartup
[ -r $HOME/.Xresources ] && xrdb $HOME/.Xresources
xsetroot -solid grey
vncconfig -iconic &
xterm -geometry 80x24+10+10 -ls -title "$VNCDESKTOP Desktop" &
twm &

After replacing the last line, the xstartup file should now appear as follows:

[oracle@localhost ~]$ cat .vnc/xstartup
#!/bin/sh

# Uncomment the following two lines for normal desktop:
# unset SESSION_MANAGER
# exec /etc/X11/xinit/xinitrc

[ -x /etc/vnc/xstartup ] && exec /etc/vnc/xstartup
[ -r $HOME/.Xresources ] && xrdb $HOME/.Xresources
xsetroot -solid grey
vncconfig -iconic &
xterm -geometry 80x24+10+10 -ls -title "$VNCDESKTOP Desktop" &
gnome-session &

After running vncserver, if the GNOME desktop GUI does not load when you connect with the VNC viewer, then try replacing the contents of xstartup with the following:

#!/bin/sh
# Add the following line to ensure you always have an xterm available.
( while true ; do xterm ; done ) &
# Uncomment the following two lines for normal desktop:
unset SESSION_MANAGER
exec /etc/X11/xinit/xinitrc
[ -x /etc/vnc/xstartup ] && exec /etc/vnc/xstartup
[ -r $HOME/.Xresources ] && xrdb $HOME/.Xresources
xsetroot -solid grey
vncconfig -iconic &
xterm -geometry 80x24+10+10 -ls -title "$VNCDESKTOP Desktop" &
gnome-session &

Note that you need to kill the vncserver session and restart it for the changes to take effect. For example, to kill the vncserver session 1, issue the following command:

vncserver -kill :1

Then rerun ‘vncserver’ to restart the VNC server session and reconnect with the VNC viewer.

Reference:

http://wiki.centos.org/HowTos/VNC-Server