Notes on use of Micro X-Win

Notes on Using Micro X-Win X Server for PCs

• General Information
• How to Set up Micro X-Win
• How to Use Micro X-Win
• Frequently Asked Questions

General Information about Micro X-Win

Micro X-Win is a X-Server for PC based platforms, enabling you to run programs using the X Windowing System on a remote machine and have the display sent to your local PC. Note that despite a common inclination to think the nomenclature should be reversed, in the true definitions of what a client and a server consist of, for the X Windowing System the server resides on the machine in which the graphics will be displayed (ie on the PC), while the application program running on the remote system is properly the client.

Micro X-Win is made by StarNet Communications and is available through a volume site purchase agreement with the campus software licensing group

How to Set Up Micro X-Win

Micro X-Win comes with two programs, the actual X Server and a configuration utility called X-Util. X-Util can be started directly from the menu or from X-Win (after X-Win is started, there will be an icon on the toolbar at the bottom of the screen. Click on that icon and select X-Util.) Before you can use Micro X-Win effectively you need to configure it. In particular, you should define sessions for those hosts which you plan to connect to using X-Win. As this configuration is necessarily user specific, PCS cannot provide an useful common departmental configuration, and so can only provide guidelines on how to configure it for yourself.`

Although there are many configurable options for this program, we will only touch on a few of the most important ones. The first one is to select the default window mode. This is done under the options menu of X-Util (although it can also be selectively overridden for specific sessions, as will be mentioned again later). PCS recommends that you use the Multiple window mode, in which case X11 windows will appear intermixed with MS Windows on your screen. Single window mode will put all your X11 windows within a single window, which makes it difficult to move between local and remote applications, although if used with XDMCP it can make things appear more like you are sitting at the remote console. However, XDMCP connections put more of the display work on the remote machine, which can overload the remote box if a number of people use it that way, so multiple windows mode is recommended.

The next step is to configure sessions. A session encompasses logging into a machine and opening some applications, usually one of which is a session manager type of program from which you can open other applications as desired. To define a session, select the Sessions menu on X-Util, and select either New Session or Edit Session. You will generally use New Session to create new sessions and Edit Session to modify existing sessions, although if you are defining sessions which are similar you can use Edit Sessions to open the edit dialog on an existing session, and change the session name to duplicate an existing session.

In the sessions dialog, it will ask you for a session name, which is simply a descriptive name for the session. It can be anything you like, and it is what will appear in the menu when you request X-Win to open a session. PCS suggests that you choose something like the hostname of the machine you want to connect to. Note: If you change the session name on an existing session and save, it does not rename the session, but instead creates a new session under the new name with the properties set (and leaving the session under the old name the same). This is an useful trick for copying sessions if creating a few sessions with very similar properties. To actually rename a session, copy it in this fashion, then delete the old session under the sessions menu.

The next step is to select the connection mode. For security reasons, you should only use rexec or XDMCP. XDMCP will connect in a manner similar to that which you would see if actually sitting at the machine (very similar if you also set to single window mode and run in a full screen display), however, it also uses more of the remote systems resources. PCS generally recommends using rexec (even though somewhat less secure) in most situations, as it places a lighter load on the network and remote system. (The security problem with rexec is that the passwords cross the network as plaintext, which makes it susceptible to sniffing attacks. However, the departmental network is switched, reducing the effectiveness of such sniffing attempts, and most of the department still uses telnet which has similar problems. If security is a concern, please contact PCS via physhelp to discuss the matter.)`

If you are using XDMCP, you need only specify the hostname of the remote machine, and optionally a login name and password (if not specified, it will prompt for). Note that the remote machine must be willing to manage your display; this is the case with most PCS maintained machines.

If you are using rexec, you will need to specify a command to be run on the remote machine, and optionally a login name and password (which will be prompted for if not specified). The command name should reflect a script to run, opening any windows, etc. On the PCS maintained clusters, the following scripts exist for your convenience:

Cluster	Command line in X-Win session config. screen
NSCP-I (AIX)	/usr/local/bin/start_dash $MYIP
PNCE-Unix/NSCP-II/Glue	/dept/phys/local/bin/start_dash $MYIP

(MYIP is an environmental variable defined by Micro X-Win containing the IP address of the PC the X server is running on.) If you dislike the standard startup (which is to display the dash> menu at the top of the screen), you can copy the named file and customize it. All commands but the last should be run in the background, and the one which is not run in the background is effectively the session manager (when it exits, the session is over). Note: On machines running Saber menu, note that both the Saber menu and dash try to place themselves as the top line of your screen. You may need to minimize Saber menu to see the dash menu.

For either rexec or XDMCP sessions, you can also specify whether the session should be Auto Startup, in which case it comes up automatically when you start Micro X-Win, and whether to Send Xauth information, which is useful if you put authentication security on your X server. You can also override the windows setting for that particular session, or just leave it as default.