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XenServer Virtual Machine Installation Guide Installing Linux VMs 24
the appropriate Red Hat Linux x86 Installation Guide for details regarding installing additional software
on your VM.
2. Open the GDM configuration file with your preferred text editor and add the following lines to the file:
[server-VNC]
name=VNC Server
command=/usr/bin/Xvnc -SecurityTypes None -geometry 1024x768 -depth 16 \
-BlacklistTimeout 0
flexible=true
• With configuration files on Red Hat Linux 3 and 4, this should be added above the [server-Stan-
dard] section.
• With configuration files on Red Hat Linux 5, this should be added into the empty [servers] section.
3. Modify the configuration so that the Xvnc server is used instead of the standard X server:
• If you are using Red Hat Linux 3 or 4, there will be a line just above that that reads:
0=Standard
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 the section called “Checking runlevels” for further details.
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 3, use redhat-config-securitylevel-tui.
For Red Hat Linux 4 and 5, use system-config-securitylevel-tui.