Differences between version 3 and previous revision of HowToXDMXterm.
Other diffs: Previous Major Revision, Previous Author, or view the Annotated Edit History
| Newer page: | version 3 | Last edited on Thursday, October 21, 2004 5:37:13 pm | by AristotlePagaltzis | Revert |
| Older page: | version 2 | Last edited on Friday, June 7, 2002 1:07:51 am | by perry | Revert |
@@ -1,1655 +1 @@
-XDM and X Terminal mini-HOWTO
-!!!XDM and X Terminal mini-HOWTO
-!Kevin Taylor
-
- kevin@northants.lug.org.uk
-
-
-
-__Revision History__Revision v1.002002-05-16Revised by: KTMinor updates to all sections. Added details of Windows/Linux interoperability.
-Added section on starting XDM. Added details of KDM and GDM. Added new software
-resources.Revision v0.0514 November 2000Revised by: KTAdded cross-references to other !HowtosRevision v0.046 November 2000Revised by: KTUpdates after first public draft.Revision v0.033 July 2000Revised by: KTMinor updates from first commentsRevision v0.0228 June 2000Revised by: KTFirst SGML source draft from HTML sourceRevision v0.0127 June 2000Revised by: KTFirst HTML source draft
-
-
-
-
-
- This document describes the basic ideas for using XDM to manage
-X terminals. It is not meant to be a comprehensive discussion
-of all the features of XDM, but a gentle introduction to what XDM
-can do.
-
-
-
-
- For a full discussion about the installation and configuration
-of X terminals, please refer to the 'Thin-client' HOWTO, from
-the Linux Documentation Project or the Linux Terminal Server Project
-(see Section 7).
-
-
-
-
-
-
-----; __Table of Contents__; 1. Introduction: ; 1.1. Copyright Information; 1.2. Disclaimer; 1.3. New Versions; 1.4. Credits; 1.5. Feedback; 1.6. To do; 2. Basic Concepts: ; 2.1. What is covered; 2.2. About this document; 3. XDM: ; 3.1. What is XDM; 3.2. What is an X terminal; 3.3. Some Terminology; 3.4. What can XDM do; 4. Configuring XDM: ; 4.1. Configuration Files; 4.2. Configuring XDM to Manage X Servers; 4.3. Configuring XDM to Receive Queries; 4.4. Starting X; 4.5. Starting XDM; 4.6. The Chooser Application; 4.7. Alternatives to XDM; 5. Advanced Configuration Options: ; 5.1. Configuration Sets; 5.2. X Resources; 6. Common Configurations: ; 6.1. Linux to Linux; 6.2. Linux to Other Systems; 6.3. Other Systems to Linux; 7. Resources
-!!!1. Introduction----
-!!1.1. Copyright Information
-
- This document is copyrighted (c) 2000-2002 Kevin Taylor and is
-distributed under the terms of the Linux Documentation Project
-(LDP) license, stated below.
-
-
-
-
- Unless otherwise stated, Linux HOWTO documents are
-copyrighted by their respective authors. Linux HOWTO documents may
-be reproduced and distributed in whole or in part, in any medium
-physical or electronic, as long as this copyright notice is
-retained on all copies. Commercial redistribution is allowed and
-encouraged; however, the author would like to be notified of any
-such distributions.
-
-
-
-
- All translations, derivative works, or aggregate works
-incorporating any Linux HOWTO documents must be covered under this
-copyright notice. That is, you may not produce a derivative work
-from a HOWTO and impose additional restrictions on its
-distribution. Exceptions to these rules may be granted under
-certain conditions; please contact the Linux HOWTO coordinator at
-the address given below.
-
-
-
-
- In short, we wish to promote dissemination of this
-information through as many channels as possible. However, we do
-wish to retain copyright on the HOWTO documents, and would like to
-be notified of any plans to redistribute the HOWTOs.
-
-
-
-
- If you have any questions, please contact
-`linux-howto@metalab.unc.edub
-
-
-----
-!!1.2. Disclaimer
-
- No liability for the contents of this documents can be accepted.
-Use the concepts, examples and other content at your own risk.
-As this is a new edition of this document, there may be errors
-and inaccuracies, that may of course be damaging to your system.
-Proceed with caution, and although this is highly unlikely,
-the author(s) do not take any responsibility for that.
-
-
-
-
- All copyrights are held by their by their respective owners, unless
-specifically noted otherwise. Use of a term in this document
-should not be regarded as affecting the validity of any trademark
-or service mark.
-
-
-
-
- Naming of particular products or brands should not be seen
-as endorsements.
-
-
-
-
- You are strongly recommended to take a backup of your system
-before major installation and backups at regular intervals.
-
-
-----
-!!1.3. New Versions
-
- The latest version number of this document may be
-obtained from
- The Northants LUG, UK Project Pages
-.
-
-
-----
-!!1.4. Credits
-
- Thanks go to the following people for help with information and
-proof reading of the document.
-
-
-
-
- Scot W Stevenson for the original X terminal mini-howto document,
-from 1995, on which some of the material for the section on advanced
-xdm-config configurations was obtained.
-
-
-
-
- Members of the Northants LUG, UK for proof reading the document.
-
-
-
-
- The writers of the XDM, Xserver man pages and the default XDM scripts.
-
-
-
-
-
-
-
-
-; Credits for .05:
-
- Everyone who commented on the earlier versions, including Neil Zanella,
-Rafael Herrera, Paul Hornshaw, Clive Jones, Robert de Geus, Alex Schenkman,
-Richard Kaszeta, Malcolm Herbet
-
-
-; Credits for 1.00:
-
- The following people provided feedback and comments which have led up to
-the 1.00 release: Alan James, Stephen Eglen, Malcolm Hunter, Holgar Hoffman,
-Patrick Rynhart, Amedeo Lanza, Alexander Skopalik, Mike Banahan.
-
-
-
-
-
-----
-!!1.5. Feedback
-
- Feedback is most certainly welcome for this document. Without
-your submissions and input, this document wouldn't exist. Please
-send your additions, comments and criticisms to the following
-email address: `xdm-mini@northants.lug.org.ukb.
-
-
-----
-!!1.6. To do
-
- I probably ought to mention some details about the following at
-some point ...
-
-
-
-
-
-*
-
- Debugging problems with XDM.
-
-
-
-*
-*
-
- FAQs and common mistakes
-
-
-
-*
-
-
-----
-!!!2. Basic Concepts----
-!!2.1. What is covered
-
- This document describes the basic concepts behind using XDM
-(the X Display Manager) to manage X terminals and X servers,
-in order to provide 'thin-client' computing, using Linux.
-
-
-
-
- X (or the 'X Window System') is the windowing and graphics environment
-of choice for Unix systems. Its particular strength (and the key bit
-that we are interested in for this document) is that it separates the
-running applications (web browser, word processor, etc) from the actual
-graphics screen and input devices (mouse, keyboard, etc) via a network
-communications mechanism.
-
-
-
-
- Essentially, this means that you can be running
-an application on one machine, but have its input and output redirected
-to another machine via a network. This is the key feature that makes
-an X terminal possible.
-
-
-
-
- This document should be treated as a 'getting started with XDM' document,
-in that it describes the basic terms and concepts for using XDM and
-X terminals, with simple examples that provide the minimum amount of
-security.
-
-
-
-
- The reader is advised to consult the list of resources provided at
-the end of the document in order to proceed beyond these basic
-facilities - in particular, the configuration of the 'authentication'
-and security settings should be examined, as the examples given in
-this document utilise the least secure modes of operation.
-
-
-
-
- Please note - the majority of the information in this document was obtained from
-systems running Debian 2.1, SuSE 6.4, Mandrake 7.0 and !RedHat 6..
-
-
-
-
- This document does not discuss the installation or
-configuration of a network or X on Linux. Please refer to the
-appropriate HOWTO documents from the Linux Documentation Project for
-details (see Section 7).
-
-
-
-
- This document also does not attempt to describe how to install and configure
-Linux for operation as an X terminal. For this information, please refer
-to the 'thin-client' HOWTO document, provided as part of the Linux Documentation
-Project, or the Linux Terminal Server Project (see Section 7).
-
-
-----
-!!2.2. About this document
-
- This document came about because I wanted to experiment with Linux
-on a 486 PC as an X terminal to my main Linux box.
-
-
-
-
- After reading the man pages, specifications and current howto documents
-relating to XDM and X terminals, I ended up getting really confused
-about where XDM was supposed to run and confusing XDM servers with
-X servers and the like, and so after an evening or two of
-experimentation, this document was born.
-
-
-
-
- Once the basic terminology has been sorted out, the documentation
-for XDM and self-documenting sample files make very good reading
-- I just could not find a simple introduction to the basic concepts
-anywhere to get me started. Hopefully this document could prove
-to be a suitable introduction to someone in a similar position to
-me.
-
-
-
-
- Oh, and in case you are wondering, a 486dx2/66 with 16 Mb RAM
-makes a fine X terminal!
-
-
-----
-!!!3. XDM----
-!!3.1. What is XDM
-
- Put simply, XDM (the X Display Manager) can be thought of as a graphical
-replacement for the command line 'login' prompt. In reality, it can
-actually do much more than that.
-
-
-
-
- Typically, it would be started by the 'root' user (or the system startup
-scripts) on power up, and would present a user with a graphical login
-prompt. It will then manage the users X session once they login -
-i.e. it will initiate the running of their window manager and applications.
-
-
-
-
- This could be considered a typical 'simple local machine login'
-configuration, as may be found installed by many Linux distributions
-by default. However, XDM can also manage remote X servers and provide
-login prompts to remote 'X terminals'. In short, it is not limited to
-the local machine - it can easily manage other machines connected via
-a network.
-
-
-
-
- XDM is a very configurable utility and this document will only just
-'scratch the surface' of what may be achieved. This document aims to
-provide enough information to configure your X terminals and application
-servers to connect to each other. The reader is referred to
-Section 7 for further information on the topics
-discussed here.
-
-
-
-
- A note on security: X (in its default configuration) and XDMCP are not
-particularly secure. I am assuming that you are running X on a
-'trusted' network and that security is not an issue.
-For details of how to tighten up your X connections
-(and more details about using the networking capabilities of X) please
-refer to the 'Running Remote X Applications' Howto document, which is
-also part of the LDP (see Section 7).
-
-
-----
-!!3.2. What is an X terminal
-
- This term could be used to cover various configurations, but at its
-simplest, is a machine with a network connection, keyboard,
-mouse and monitor, configured to run the X Windows System to connect
-to an application server somewhere on the network.
-
-
-
-
- There are several configurations of 'X terminal' with varying levels
-of functionality, ranging from completely diskless terminals to full
-X workstations.
-
-
-----
-!!3.3. Some Terminology
-
- Before I go any further, I ought to explain the terms I will be using
-in this document. When talking about X, there is quite a lot of
-confusion over what is serving facilities to what. This is especially
-true when you are considering distributed sessions over a network
-involving X terminals. I will be using the terms described below.
-
-
-
-
-
-
-
-
-; Diskless X terminal:
-
- This would be a machine with no local disks, that would perform its
-boot up from an EPROM (or similar) and utilises a network connection to a
-server. It would obtain its
-network configuration, operating system, system configuration and all
-applications from the server. Once booted however, this
-would be the same as a 'dumb X terminal' (see below). Typically this
-configuration would use a combination of the following network protocols
-in order to boot: BOOTP, DHCP, TFTP, etc. Refer to
-Section 7
-for some references that detail how to build diskless X terminals.
-
-
-; Dumb X terminal:
-
- This would be a machine that boots from its local disk into an operating
-system, and starts the 'X server' program and nothing more. Somehow, a login
-prompt would be provided on the machine, to enable a user to login to an
-'application server' somewhere on the network.
-
-
-; X Workstation:
-
- This would be similar to a dumb X terminal, but would provide the option
-of logging on to the local machine itself, hence would be quite capable of
-becoming a standalone workstation (i.e. no network connectivity) if required.
-Most distributions can be configured 'out of the box' as a stand-alone
-X Workstation, with a graphical login prompt.
-
-
-; Application Server:
-
- In the context of this document, I use the term 'application server' to
-describe a machine that will provide the applications (X clients) that our X
-terminal will want to run. This can include everything from editors and browsers,
-through to the actual 'Window Manager' itself.
-
-
-; X Server:
-
- This is the program that manages the display of a machine with a physical
-console (display, keyboard, mouse, etc). It can be thought of as a combined
-graphics card, keyboard and mouse 'driver'.
-This will provide these facilities as a service to X clients (hence the term
-'server'). Please refer to the X User Howto in
-Section 7
-for more details.
-
-
-; X Client:
-
- This is an application that requires the use of an X server to access
-input (keyboard and mouse) and output (display). An X client cannot produce
-output without the services of the X server. The X server could be
-running locally (on the same machine, as is the case with an X
-workstation) or elsewhere on the network
-(as is the case with an X terminal connecting to an Application Server).
-
-
-
-
-
-
-
- From the above descriptions, an X Workstation could be thought of
-as consisting of a dumb X terminal and application server running on the same
-machine.
-
-
-
-
- This document will be looking at the architecture of the various options
-listed above and will describe the role that XDM can play in configuring
-them.
-
-
-----
-!!3.4. What can XDM do
-
- XDM is responsible for providing the user with a login
-prompt and initiating their X session. It can manage local sessions (i.e. people
-logging into an X workstation) or sessions on remote machines, via a connection
-to an application server, from a diskless or dumb X terminal.
-
-
-
-
- XDM would typically run on an application server, to permit users to logon
-and run applications from that server.
-
-
-
-
- There are 2 main ways that XDM can interact with an X Server:
-
-
-
-
-
-*
-
- XDM accepts queries from X server
-
-
-
-*
-*
-
- XDM manages X server
-
-
-
-*
-
-
-----
-!3.4.1. XDM accepts queries from X Server
-
- The communications between XDM and the actual 'X server' (the machines
-with the physical screen/keyboard/mouse/etc) are handled via XDMCP the
-'X Display Manager Control Protocol'.
-
-
-
-
- This permits X servers to send out queries to servers running XDM.
-Effectively, the X server has to say 'I have someone wanting to login -
-please give me a login prompt'. In this mode of operation, XDM will
-not do anything unless it is asked to by your X server.
-
-
-
-
- The query from the X server can take one of 3 forms:
-
-
-
-
-
-*
-
- Direct query: the X server contacts a named host, requesting that XDM
-on that host presents a login prompt on its display.
-
-
-
-*
-*
-
- Broadcast: the X server sends out a broadcast message to the network,
-and the first server running XDM that responds to the broadcast will
-be the one to present the login prompt on its display.
-
-
-
-*
-*
-
- Indirect query: the X server contacts a named host, but asks it which
-other hosts it knows about on the network. The named host will then
-present the user with a list of hosts to choose from, and will then
-go on to initiate communications with the selected host resulting in
-the selected host presenting a login prompt on the X servers display.
-
-
-
-*
-
-
-
-
- There are several other options, but these will not be described here
-- refer to the XDM and XDMCP documentation in Section 7
-for more details.
-
-
-----
-!3.4.2. XDM Manages X Server
-
- If you have a set of machines (e.g. diskless or dumb X terminals) that just
-end up running an X server, all designed to provide a login prompt to a
-single application server, then it is possible to configure XDM on the
-application server to connect back to each X server and present its login
-prompt on each display automatically.
-
-
-
-
- In this mode of operation, XDM will actively 'push out' a login prompt
-to any listed X server that it knows about, without waiting for
-a query from the X servers themselves.
-
-
-
-
- In this case, the configuration file 'Xservers' (see later) lists each
-machine (including the local display, if required) to which XDM should
-connect, to display its login prompt.
-
-
-
-
- This configuration, when used with no remote X servers listed in the
-configuration, is the typical configuration used for a X workstation,
-in order to present a user with a graphical login to the local machine
-he is working on. As stated earlier, most distributions will support
-this configuration 'out of the box' in order to present the user with
-a local graphical login prompt.
-
-
-
-
- Note: XDM must be permitted to connect to the X servers in question - so
-the access control on the X servers must be configured accordingly.
-
-
-----
-!!!4. Configuring XDM
-
- This section covers what needs to be configured for XDM to perform
-the functions described so far in this document.
-
-
-
-
- In each case, the configuration described is the minimum necessary to
-accomplish each goal. In most cases this means that the configuration
-is also the least secure. Please refer to some of the additional
-documentation listed in Section 7
-for information about securing XDM and X terminals
-(in particular the 'Running Remote X Applications Howto' from the LDP).
-
-
-----
-!!4.1. Configuration Files
-
- This describes the following scheme of XDM configuration files:
-
-
-
-
-
-*
-
- xdm-config
-
-
-
-*
-*
-
- Xaccess
-
-
-
-*
-*
-
- Xservers
-
-
-
-*
-*
-
- Xresources
-
-
-
-*
-
-
-
-
- These must be setup for the machine actually running XDM itself. They will typically be
-found in (Debian 2.1. Mandrake 7..2, !RedHat 6.2):
-
- /etc/X11/xdm
-
-or (SuSE 6.4):
-
- /usr/X11R6/lib/X11/xdm
-
-
-
-
-
-
-
-
-
-; xdm-config:
-
- Defines the names and locations of the other configuration files and the basic
-access permissions. For all distributions considered for this document,
-the file names were as listed here (but sometimes the locations varied).
-
-
-
-
- This also defines the scripts to be run for the various state
-transitions for an X session, i.e. on startup, etc. You should
-not need to change these, as most distributions would appear to
-come with this pre-configured for you.
-
-
-
-
- Note that XDM managed X sessions have a different set of startup
-and configuration scripts to X sessions started via xinit or startx
-(i.e. non-XDM managed X sessions).
-
-
-
-
- Some distributions (e.g. Redhat 7.1) include the following line in this configuration
-file, which will prevent XDM from listening for queries:
-
- !DisplayManager.requestPort:
-
-This must be commented out as follows:
-
- !!DisplayManager.requestPort:
-
-
-
-; Xaccess:
-
- Determines which machines can connect to XDM - i.e.
-from which other machines on the network we are accepting XDMCP
-queries. If a machine is not listed in this file, then it will not
-be able to request a login prompt from XDM.
-
-
-; Xservers:
-
- Contains a list of machines that XDM will connect to, to provide a
-login prompt, automatically - i.e. those machines already running an X
-server, but would like this machine to provide the login prompt.
-
-
-
-
- This is only required for 'XDM Managed X Servers'. You do not need
-any entries in this file if you will be relying on remote X servers
-to query XDM.
-
-
-
-
- When running as a stand-alone 'X Workstation', there is usually a
-single entry in this file, listing just the localhost.
-
-
-; Xresources:
-
- Details of the X properties used by the XDM widgets (e.g. size of the
-login 'box', colours, bitmap backgrounds, etc).
-
-
-
-
-
-----
-!!4.2. Configuring XDM to Manage X Servers
-
- An entry must be placed in the Xservers file for each X server
-that XDM will be presenting a login prompt on. This could include
-the local machine and/or a list of remote machines.
-
-
-
-
- Example
-
- # First the local host
-:0 local /usr/bin/X11/X vt7
-#
-# Then the remote hosts
-emma:0 foreign
-alex:0 foreign
-
-
-
-
-
- This will start XDM on the local machine and also present
-a login screen on the X servers running on the hosts 'emma' and 'alex' (assuming that
-permissions have been setup on 'emma' and 'alex' such that this machine
-is permitted to connect to the running X servers).
-
-
-
-
- Note that it is possible to specify the host and display (:, :1, etc)
-if required. This is useful, for example, if you are running multiple X servers on a
-single machine, etc.
-
-
-----
-!!4.3. Configuring XDM to Receive Queries
-
- The file Xaccess determines which hosts may query XDM on this machine,
-in order to request a login prompt.
-
-
-
-
- Example
-
- # First line for direct queries
-*
-# Following line for indirect queries
-* CHOOSER BROADCAST
-
-
-
-
-
- This means that any host may request a login prompt via XDM (the first '*')
-using a direct query.
-
-
-
-
- The 'CHOOSER' line specifies which hosts can connect to XDM using
-indirect queries - in this case, any host may query this machine for
-a list of potential hosts to connect to (the second '*' line).
-
-
-
-
- 'BROADCAST' means that the 'chooser' application on this machine
-will obtain its list of available servers (that will also be running XDM)
-via network broadcast queries. I will talk about the 'chooser' later.
-
-
-
-
- It is possible to place specific host names or specifications of network IP
-addresses (e.g. a whole IP network or specific hosts) in these entries (and there
-are also other indirect queries possible, without using the chooser)
-but this is not described here (refer to Section 7
-for some links to more information).
-
-
-----
-!!4.4. Starting X
-
- The way you start the X server itself, will depend upon how you want it to
-interact with XDM locally and remotely.
-
-
-
-
-
-
-
-
-; X Workstation: XDM and local X server:
-
- XDM will normally start X automatically for you and XDM will usually
-be configured to run as part of the startup process (via the init scripts).
-Most distributions have a specific 'run-level' for starting the system up
-with a graphical login prompt.
-
-
-
-
- The Xservers file would typically contain a single entry - that of the
-local host, and the Xaccess file would only need to permit access from
-the local host.
-
-
-; X Terminal: Remote XDM:
-
- Just start X with no clients, with access permissions such that the
-remote XDM is able to connect when it starts up. The following will start
-X with no access control:
-
- /usr/X11R6/bin/X -ac
-
-
-
-
-
- When the remote XDM is started, it will 'push out' a login prompt to
-all such configured X servers (as listed in its Xservers file).
-
-
-; X Terminal: Query a remote XDM:
-
- Recall there are 3 modes for queries: direct, indirect and broadcast
-(direct for a single host, indirect for a list of hosts or broadcast for
-the first host that replies):
-
- /usr/X11R6/bin/X -query the.remote.host
-/usr/X11R6/bin/X -indirect the.remote.host
-/usr/X11R6/bin/X -broadcast
-
-
-
-
-
-
-
-
- In each case, X will probably have to be started as root.
-
-
-
-
- It is possible to have a machine automatically start X and perform a query
-for a running XDM on the network. One way is to 'hijack' the inittab setting
-for running as a graphical login (this is runlevel 5 on Debian and
-Redhat based systems, and 3 for SuSE - this example assumes runlevel
-5 throughout). This is often the line beginning x:5 towards the end of /etc/inittab.
-Set this to (or add it if it doesn't exist):
-
- x:5:respawn:/usr/X11R6/bin/X -broadcast
-
-Replacing -broadcast with -direct or -indirect, etc. as required. You may have to
-change your default runlevel to be 5 too, (and then reboot), as follows:
-
- id:5:initdefault:
-
-
-
-----
-!!4.5. Starting XDM
-
- In a standard X workstation configuration, XDM would typically be started up by
-specifying the default initial run-level to be that corresponding to a full graphical
-login. On Redhat and Debian based systems this is usually runlevel 5. On SuSE it is
-run-level 3.
-
-
-
-
- It is possible to run XDM automatically on startup by changing the default runlevel
-to that described above. This is configured in /etc/inittab as follows:
-
- id:5:initdefault:
-
-
-
-
-
- Alternatively it is possible to add a startup script for XDM itself to the rc scripts
-in the startup directories (/etc/rc.d/ for Redhat/Debian), to start and stop XDM in a
-similar manner to other services on a Linux machine.
-
-
-
-
- The following script is suitable for a Redhat (and probably Mandrake) based system,
-and should be saved as /etc/rc.d/init.d/xdm. You will have to enable it using
-'chkconfig --add xdm'.
-
- #!/bin/sh
-# xdm start/stop script for !RedHat based systems
-#
-# chkconfig: 234 60 60
-# description: xdm permits remote users to logon to this X display
-# processname: /usr/X11R6/bin/xdm
-# config: /etc/X11/xdm/xdm-config
-# source function library
-. /etc/rc.d/init.d/functions
-[ -x /usr/X11R6/bin/xdm
] || exit
-prog=/usr/X11R6/bin/xdm
-RETVAL=
-start () {
-echo -n $"Starting $prog: "
-# start daemon
-daemon $prog
-RETVAL=$?
-echo
-[[ $RETVAL = 0 ] 88 touch /var/lock/subsys/xdm
-return $RETVAL
-}
-stop () {
-echo -n $"Stopping $prog: "
-killproc $prog
-RETVAL=$?
-echo
-[[ $RETVAL = 0 ] 88 rm -f /var/lock/subsys/xdm
-return $RETVAL
-}
-restart () {
-stop
-start
-RETVAL=$?
-return $RETVAL
-}
-# See how we were called.
-case "$1" in
-start)
-start
-;;
-stop)
-stop
-;;
-status)
-status $prog
-RETVAL=$?
-;;
-restart)
-restart
-;;
-condrestart)
-# only restart if it is already running
-[[ -f /var/lock/subsys/xdm ] 88 restart || :
-;;
-reload)
-echo -n $"Reloading $prog: "
-killproc $prog -HUP
-RETVAL=$?
-echo
-;;
-*)
-echo $"Usage: $0 (start|stop|restart|condrestart|reload|status)"
-RETVAL=1
-esac
-exit $RETVAL
-
-
-
-----
-!!4.6. The Chooser Application
-
- When XDM receives an indirect query, and assuming that the appropriate options
-have been specified in Xaccess for the 'chooser' application, it can
-provide the user with a list of other XDM managed servers that it
-knows about.
-
-
-
-
- In this mode of operation, instead of the normal XDM login prompt,
-the user will be presented with a 'chooser' application, which will
-provide a list of detected hosts on the network that are currently
-accepting XDM connections.
-
-
-
-
- When I first tried the use the chooser, I found that the Xresources
-files that came with my SuSE and Debian systems, specified a size for
-the chooser widget that was too big for the screens ... The following
-line from the Xresources file fixed that:
-
- Chooser*geometry: 700x500+300+200
-
-
-
-
-
- The chooser will obtain its lists of hosts by one of two methods:
-
-
-
-
-
-*
-
- Broadcast Query: In this mode a request is broadcast over the network,
-and a list is built up from the replies received from other application
-servers running XDM.
-
-
-
-*
-*
-
- Explicit Listing: It is possible to provide a list of hosts for
-the chooser in the Xaccess file, as follows:
-
- %hostlist emma alex liam abigail
-* CHOOSER %hostlist
-
-This will mean that the hosts emma, alex, liam and abigail will all be
-listed as candidates - even if one of the machines is down
-(there is often a button to 'ping' the host to see if it is
-running, before trying to connect to it).
-
-
-
-*
-
-
-
-
- Not that it is possible to include the localhost in the list of machines
-known to the chooser as well. XDM should be configured not to startup on
-the local console display though. Login should always be performed via
-an indirect query to the local chooser application, then the localhost
-should appear alongside any other hosts on the network.
-
-
-----
-!!4.7. Alternatives to XDM
-
- Both KDE and Gnome have their own application to replace the standard
-XDM. They do similar things and are well documented.
-As far as providing remote X access, there is a single setting in the configuration
-file for the application to enable XDMCP support.
-
-
-
-
-
-
-
-
-; KDM: KDE Display Manager:
-
- The following must be set in the KDM configuration file (/usr/share/config/kdm/kdmrc
-for a Mandrake 8.1 system):
-
- [[Xdmcp]
-Enable=True
-
-
-
-; GDM: Gnome Display Manager:
-
- The following must be set in the GDM configuration file (/etc/X11/gdm/gdm.conf):
-
- [[Xdmcp]
-Enable=True
-
-To have GDM running without starting the local X server, comment out the line
-
- =Standard
-
-in the 'servers' section of the configuration file too.
-
-
-
-
-
-----
-!!!5. Advanced Configuration Options----
-!!5.1. Configuration Sets
-
- The xdm-config file provides a rich set of options, when it comes
-to defined scripts and other configuration files. In many cases,
-the defaults provided with your distribution should be fine, but
-for those of you who want more ...
-
-
-
-
- The names of the startup scripts and configuration files used by
-XDM are determined by a series of statements in the top-level
-xdm-config file. This permits you to configure a different set
-of files for different X servers and X terminals, with different
-abilities.
-
-
-
-
- For example, say you are using XDM to manage your local display, but
-also want it to accept queries from other X terminals on the network.
-It is possible to specify a different Xresources file for each of these
-cases, by using the following 2 lines in xdm-config:
-
- !DisplayManager._.resources /etc/X11/xdm/Xres_
-!DisplayManager*resources /etc/X11/xdm/Xresources
-
-This will use Xres_0 for the local display (_0 is the XDM way of
-saying :) and Xresources for everything else (the '*').
-
-
-
-
- Similarly, if you wanted a particular resource file for a specific
-host, you would use an entry like the following:
-
- !DisplayManager.host_.resources /etc/X11/xdm/Xres_host_
-
-
-
-
-
- Note that XDM configuration files use the terminology host_, where you
-would normally use host:, to designate 'display 0 on host'.
-
-
-
-
- If you look over your default xdm-config file, you will probably
-find that it has been setup so that your local X server has different
-files to the remote ones anyway, as different things must be performed
-on startup and reset of the server. My Debian file has the following
-for local servers:
-
- !DisplayManager._.resources: /etc/X11/xdm/Xresources_
-!DisplayManager._.setup: /etc/X11/xdm/Xsetup_
-!DisplayManager._.startup: /etc/X11/xdm/Xstartup_
-!DisplayManager._.reset: /etc/X11/xdm/Xreset_
-
-and the following for remote servers:
-
- !DisplayManager*resources: /etc/X11/xdm/Xresources
-!DisplayManager*setup: /etc/X11/xdm/Xsetup
-!DisplayManager*startup: /etc/X11/xdm/Xstartup
-!DisplayManager*reset: /etc/X11/xdm/Xreset
-
-
-
-----
-!!5.2. X Resources
-
- This document has only briefly touched on the available X resources, but
-I should mention that it is possible to fully configure XDM via the Xresources
-file.
-
-
-
-
- The following may all be changed if required:
-
-
-
-
-
-*
-
- Fonts, login prompt sizes
-
-
-
-*
-*
-
- Background graphics
-
-
-
-*
-*
-
- Window Titles, etc
-
-
-
-*
-
-
-
-
- There is a more detailed discussion of XDM resources, on Richard Kaszeta's web site
-(see Section 7)
-
-
-----
-!!!6. Common Configurations----
-!!6.1. Linux to Linux
-!6.1.1. Stand-alone X Workstation
-
- This has already been mentioned several times in this document, but
-in summary, it is a PC running XDM, with a single entry in the Xservers
-file, relating to the localhost (i.e. the local machine).
-
-
-
-
- This is usually the default configuration provided by most distributions
-'out of the box'.
-
-
-----
-!6.1.2. X Terminal and Application Server
-
- XDM runs on the application server:
-
-
-
-
-
-*
-
- Xserver: Contains no entries
-
-
-
-*
-*
-
- Xaccess: Must permit the X terminal to connect
-
-
-
-*
-
-
-
-
- X terminal runs X using a direct query to the application server:
-
- /usr/X11R6/bin/X -query the.application.server
-
-
-
-----
-!6.1.3. Group of Managed X Terminals
-
- XDM runs on an application server:
-
-
-
-
-
-*
-
- Xserver: Lists each X terminal to be managed
-
-
-
-*
-*
-
- Xaccess: Must permit each X terminal to connect
-
-
-
-*
-
-
-
-
- Each X terminal, just runs X, with suitable access control to
-permit XDM to connect to it.
-
- /usr/X11R6/bin/X -ac
-
-
-
-----
-!!6.2. Linux to Other Systems
-
- It is possible to use a Linux X terminal to connect to another
-system running XDM. The same principles as above apply, but
-the specifics of configuring XDM (or its equivalent) will be
-specific to that system.
-
-
-----
-!6.2.1. Linux and Solaris
-
- You can run X on a Linux box, instructing it to query
-a Solaris machine as previously described:
-
- /usr/X11R6/bin/X -query the.solaris.server
-
-
-
-
-
- Note that you may have to configure X on the Linux
-machine to use the font server from the Solaris box.
-Although my Linux box connected and logged in fine without
-doing this, the fonts used by CDE were not displayed
-correctly.
-
-
-
-
- I have not got this to work yet, as I don't have a
-Solaris box that I have any control over - but I am
-told that a font entry in /etc/XF86config similar to
-the following should work - you may have to change the
-port number from 7200 to something else (7100 has been
-quoted at me before). Can anyone confirm that this works?
-
- !FontPath "tcp/solaris.box:7200/all"
-
-
-
-----
-!6.2.2. Linux and Windows
-
- It is not possible to use X to remotely display Windows applications
-on a Windows box. It is possible to use X to display Windows versions
-of X applications on a Linux box, using a Windows X Server and Windows
-X applications (for example the XFree86 Win32 port -
-see Section 7)
-
-
-
-
- It is possible to view Windows applications remotely on a Linux box
-using one of the following applications (which don't rely on X or XDM):
-
-
-
-
-
-*
-
- Windows Terminal Services (WTS). RDesktop is a Linux application that
-understands the 'RDP' protocol used by WTS. This enables Linux to act
-as a client to WTS (see Section 7).
-
-
-
-*
-*
-
- Vitual Network Computing (VNC). This is an excellent platform independent
-remote desktop system that provides a bi-directional 'Windows or Linux' to
-'Windows or Linux' networked desktop. It can be a bit slow, but works
-well (see Section 7).
-
-
-
-
- You can actually do quite strange things with VNC, such has having multiple
-machines connect and 'control' the desktop (and consequently 'fight' over
-control of the mouse :). It also doesn't maintain any
-state in the client, so you can leave your client, shutdown, bootup again,
-reconnect and carry on from where you left off. There is even a version
-of the viewer implemented as a Java applet, usable from any Java-enabled web
-browser.
-
-
-
-*
-
-
-----
-!!6.3. Other Systems to Linux
-
- If you have an X server for your system, it should be able to connect
-to a Linux XDM application server.
-
-
-----
-!6.3.1. Solaris and Linux
-
- I assume that you would run XDM on the Linux box as usual, and
-instruct X on Solaris to query the Linux box - does anyone have
-any information on this?
-
-
-----
-!6.3.2. Windows and Linux
-
- If you have an X server for windows that supports XDMCP queries, then
-it should be possible to configure it to query the Linux box. You should
-just run XDM on the Linux box as usual.
-
-
-
-
- There are many commercial X Server implementations for Windows, and I will
-not list them all
here. There is also a port of XFree86 to Windows, that
-makes use of the cygwin libraries (used to port many GNU/Linux tools to
-Windows - see Section 7). This works well.
-
-
-
-
- The following batch file would start the cygwin XFree86 X server on
-Windows and connect to a Linux box (or any OS/machine running XDM),
-assuming a default installation of cygwin and XFree86 in c:\cygwin
-(save it as xdm.bat):
-
- @echo off
-if "%1"=="" goto noserver
-goto allok
-:noserver
-echo Usage: xdm servername
-goto end
-:allok
-set path=%PATH%;\cygwin\bin;\cygwin\usr\X11R6\bin
-c:
-chdir \cygwin\usr\X11R6\bin
-XWin -query %1
-:end
-
-
-
-----
-!!!7. Resources
-
- This section lists some resources that have been consulted in order to
-construct this document and which provide further details to the concepts
-described.
-
-
-
-
- Many of the references listed below form part of the Linux Documentation
-Project (LDP): http://www.tldp.org/
-
-
-
-
-
-
-
-
-; The X Window System:
-
-
-
-
-
-
-*
-
- X User Howto (from the
-LDP)
-
-
-
-*
-*
-
- Running Remote X Applications Mini Howto (from the
-LDP)
-
-
-
-*
-*
-
- Man pages: X (main concepts), Xserver (X server concepts)
-
-
-
-*
-*
-
- X FAQ (on
-http://www.x.org/)
-
-
-
-*
-
-
-; Thin-clients/X terminals:
-
-
-
-
-
-
-*
-
- Thin-client Howto Document (from the
-LDP)
-
-
-
-*
-*
-
- Linux Terminal Server Project:
-http://www.ltsp.org/
-
-
-
-*
-*
-
- Setting up LTSP systems (using quiet hardware):
-http://development.gbdirect.co.uk/xterminal.html
-
-
-
-*
-*
-
- Diskless Howto Document (from the
-LDP)
-
-
-
-*
-*
-
- X terminal pages:
-http://dns.solucorp.qc.ca/xterminals
-
-
-
-*
-*
-
- Richard Kaszeta: Converting old PCs into Standalone X Terminals:
-http://www.menet.umn.edu/~kaszeta/unix/xterminal/
-
-
-
-
-*
-
-
-; XDM, XDMCP, etc:
-
-
-
-
-
-
-*
-
- Man pages: xdm
-
-
-
-*
-*
-
- XDMCP Howto Document (from the
-LDP)
-
-
-
-*
-
-
-; Software:
-
-
-
-
-
-
-*
-
- Cygwin/XFree86 (Win32): http://www.cygwin.com/
-
-
-
-*
-*
-
- VNC: http://www.uk.research.att.com/vnc/
-
-
-
-*
-*
-
- rdesktop: http://www.rdesktop.org/
-
-
-
-*
-*
-
- X Servers for Windows (and other systems): http://www.rahul.net/kenton/xsites.html
-
-
-
-*
-*
-
- GPL Java X Server: http://www.jcraft.com/weirdx/
-
-
-
-*
-*
-
- X Terminal/Diskless specific distributions: http://lwn.net/Distributions/
-
-
-
-*
+Describe
[HowToXDMXterm
] here.
