Using an Xdmcp Client

Once you've reconfigured and restarted the XDMCP server, it's time to try it with an XDMCP client—that is, an X server. The simplest configuration is usually from a Windows X server. For instance, Figure 26.3 shows the configuration utility for Xmanager.

Figure 26.3: Windows X servers typically provide a GUI tool for setting XDMCP server options.

The XDM tab shown in Figure 26.3 provides several options relating to XDMCP use:

Do Not Use XDM (Passive) This option tells the server not to use XDMCP at all. Instead, you use some other method of initiating the connection to the remote system.

XDM Query This option tells the server to connect directly to a single XDMCP server. If all works well, you'll see the XDMCP login prompt and be able to access the system.

XDM Broadcast This option tells the server to broadcast a query for available XDMCP servers and present a list to you, as shown in Figure 26.4. You can then select which remote system you want to use, whereupon you'll see that system's XDMCP login prompt.

Figure 26.4: XDMCP clients frequently enable you to pick which XDMCP server to use from a list.

XDM Indirect This option works much like XDM Broadcast, except that the server doesn't send a broadcast itself; instead, it asks the host you specify to send the broadcast and display a chooser. This option is most useful if you're trying to select from machines that reside behind a firewall that blocks broadcasts but not XDMCP logins or other X-related activity.

Note All of these options apply when you start the X server after configuring it. For instance, with Xmanager, the XDMCP option applies when you launch the program from the Xmanager icon.

If you want to use a Linux system with XDMCP as a dumb GUI terminal for another system, you can do so. The trick is to not start X in the normal way, which launches a local window manager and may present the system's own XDMCP login prompt. Instead, you launch X from a text-mode login or custom startup script and pass it the -query hostname, -broadcast, or -indirect hostname options, which work much like the options of similar names just described for Xmanager. For instance, with X not running, you might type the following command at a text-mode prompt:

$ /usr/X11R6/bin/X -indirect

This command starts X, tells the system to obtain a list of accessible systems from, and presents that list on the display. One important difference between XFree86's handling of these options and those of most Windows X servers is that XFree86 doesn't present a list of available servers if you use the -broadcast option. Instead, it connects directly to the first available server.

Tip If you have slow computers that you want to continue using, one way is to convert them into X terminals—computers that do nothing but run X in order to run programs on other systems. Install Linux on these systems, configure them to start in text mode, and create custom SysV or local startup scripts to launch X. Users can then log into other systems, using the old systems only for their displays, keyboards, and mice.

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