63
Modify it to read:
0=VNC
• If you are using Red Hat Linux 5 or greater, add the above line just below the [servers] section and
before the [server-VNC] section.
4. Save and close the file.
Restart GDM for your change in configuration to take effect, by running the command /usr/sbin/gdm-restart.
Note:
Red Hat Linux uses runlevel 5 for graphical startup. If your installation is configured to start up
in runlevel 3, change this for the display manager to be started (and therefore to get access
to a graphical console). See Section D.4, “Checking Runlevels” for further details.
D.2.3. Firewall Settings
The firewall configuration by default does not allow VNC traffic to go through. If you have a firewall between
the VM and XenCenter, you need to allow traffic over the port that the VNC connection uses. By default, a VNC
server listens for connections from a VNC viewer on TCP port 5900 + n, where n is the display number (usually
just zero). So a VNC server setup for Display-0 will listen on TCP port 5900, Display-1 is TCP-5901, and so on.
Consult your firewall documentation to make sure these ports are open.
You might want to further customize your firewall configuration if you want to use IP connection tracking or limit
the initiation of connections to be from one side only.
To customize Red Hat-based VMs firewall to open the VNC port
1. For Red Hat Linux 4 and 5, use system-config-securitylevel-tui.
2. Select “Customize” and add 5900 to the other ports list.
Alternatively, you can disable the firewall until the next reboot by running the command service iptables stop,
or permanently by running chkconfig iptables off. This can of course expose additional services to the outside
world and reduce the overall security of your VM.
D.2.4. VNC Screen Resolution
If, after connecting to a VM with the graphical console, the screen resolution is mismatched (for example, the VM
display is too big to comfortably fit in the Graphical Console pane), you can control it by setting the VNC server
geometry parameter as follows:
1. Open the GDM configuration file with your preferred text editor. See Section D.2.1, “Determining the
Location of your VNC Configuration File” for information about determining the location of this file.
2. Find the [server-VNC] section you added above.
3. Edit the command line to read, for example:
command=/usr/bin/Xvnc -SecurityTypes None -geometry 800x600
where the value of the geometry parameter can be any valid screen width and height.
4. Save and close the file.
