by Jeffery Ludwig & Justin Federici

This setup is specific to CentOS 4.2 and Fedora Core 5, but other distributions will be very similar. When running Fluent remotely on a cluster, it is necessary to setup a local server to accept incoming X11 connections. On the server (workstation) side, the following changes must be made to a stock installation:

• The firewall must be setup to allow incoming tcp on ports 6000-6020, perhaps more. Each X11 session uses a successive port so that the upper limit may be to be increased. This can be done by either adding 6000:tcp, 6001:tcp, 6002:tcp... to the other ports line in system-config-securitylevel program, or allowing all incoming traffic from the cluster.

For CentOS 4.2

• The GDM daemon must have the DisallowTCP=false option explicitly specified. This config change is made in /etc/X11/gdm/gdm.conf, there is also a factory setting that may need to be change as well. After a reboot, a ps -aux dump should show X11 running without the -nolisten option.

For Fedora Core 5

• In the file /etc/X11/xdm/kdmrc, remove the “-nolisten tcp” flag from ServerArgsLocal.

• Run /usr/bin/gdmsetup and under the Security tab, uncheck “Deny TCP”.

• Restart X11

For all systems

• xhost +grendel.che.udel.edu must be executed once every session. This is easily accomplished by adding this line to ~/.bashrc

The DISPLAY variable has the following format: 123.123.123.123.x:0. The x indicates which starting port the client program sends on. If port forwarding is needed (a router) this can be used to setup two servers behind one router.