File: LTSPManual.xml

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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"
[
<!ENTITY ldm "<command>ldm</command>ldm;">
<!ENTITY ltspfs "<command>ltspfs</command>">
<!ENTITY rdesktop "<command>rdesktop</command>">
<!ENTITY lts.conf "<filename>lts.conf</filename>">
]>
<book>
    <title>Linux Terminal Server Project Administrator's Reference</title>
    <subtitle>
        A Guide to LTSP Networks
    </subtitle>
    <bookinfo>
        <title>Linux Terminal Server Project Administrator's Reference</title>
        <authorgroup>
            <author><firstname>Scott</firstname><surname>Balneaves</surname></author>
            <author><firstname>Jordan</firstname><surname>Erickson</surname></author>
            <author><firstname>Francis</firstname><surname>Giraldeau</surname></author>
            <author><firstname>Richard</firstname><surname>Johnson</surname></author>
            <author><firstname>David</firstname><surname>Johnston</surname></author>
            <author><firstname>Chuck</firstname><surname>Liebow</surname></author>
            <author><firstname>James</firstname><surname>McQuillan</surname></author>
            <author><firstname>Jonathan</firstname><surname>Mueller</surname></author>
            <author><firstname>Gideon</firstname><surname>Romm</surname></author>
            <author><firstname>Joel</firstname><surname>Sass</surname></author>
            <author><firstname>Robin</firstname><surname>Shepheard</surname></author>
            <author><firstname>Susan</firstname><surname>Stewart</surname></author>
            <author><firstname>Brian</firstname><surname>Tilma</surname></author>
            <author><firstname>David</firstname><surname>Van Assche</surname></author>
            <author><firstname>Carol</firstname><surname>Wiebe</surname></author>
            <author><firstname>Vagrant</firstname><surname>Cascadian</surname></author>
        </authorgroup>
        <date>Aug, 2015</date>
        <edition>1.2</edition>
        <pubdate>Aug 2015</pubdate>
        <copyright>
            <year>2008</year>
            <year>2015</year>
            <holder>Scott Balneaves and other authors</holder>
        </copyright>
        <legalnotice>
            <para>
                Permission to use, copy, modify and distribute
                the software and its accompanying documentation for any
                purpose and without fee is hereby granted in perpetuity under
                the terms of the GNU GPL2,
                provided that a copy of the GNU GPL2 appears
                with it.
            </para>
        </legalnotice>
        <legalnotice>
            <para>
                The copyright holder makes no representation about the
                suitability of this software for any purpose. It is provided
                <quote>as is</quote> without expressed or implied
                warranty.  If you modify the software in any way, identify your
                software as a variant of LTSP.
            </para>
        </legalnotice>
    </bookinfo>
    <chapter id='intro'>
        <title>Linux Terminal Server Project - LTSP</title>
        <sect1>
            <title>Introduction to LTSP and Thin Client Computing</title>
            <para>
                One of the key technologies included in modern GNU/Linux
                operating systems is the Linux Terminal Server Project (LTSP)
                which allows you to boot thin clients from an LTSP server. For
                educational environments, LTSP lowers hardware costs by
                enabling the use of older or less powerful machines as thin
                clients, as well as reduced administration overhead by having
                only to install and maintain the software on the server. When
                a workstation fails, it can simply be replaced without data
                loss or re-installation of the operating system.
            </para>
            <para>
                Thin client computing has been around for a long time in the
                UNIX world. Although the implementation has evolved quite a
                bit, the concept has remained the same:
            </para>
            <orderedlist>
                <listitem>
                    <para>
                        The thin client only takes care of the basic
                        functions like display, keyboard, mouse and sound.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        The server does the heavy weightlifting. All the
                        applications run on the server, and they simply
                        display on the thin client.
                    </para>
                </listitem>
            </orderedlist>
            <para>
                Because the thin clients have a limited number of tasks to
                manage, the hardware for the thin client can be small and
                cheap. The thin clients themselves are basically maintenance
                free. They last longer because they have no storage with
                moving parts like hard disks. If they break no data is lost
                since nothing is stored on the client itself. Simply swap the
                client with another one and go back to work. If your thin
                client is stolen or put in the trash, no data ends up in the
                hands of unauthorized people.
            </para>
            <para>
                The terminal server runs all applications and contains all
                the data. All the regular maintenance (software updates,
                administration) takes place on the terminal server. The number
                of thin clients that a terminal server can support is
                proportional to the power of the server. Because GNU/Linux
                makes efficient use of resources, you can support a surprising
                number of thin clients from a machine which might only be
                considered a powerful single user system running other
                operating systems. Please see for more details.
            </para>
            <para>
                In a thin client computing environment, the stability of the
                server is important. It's important to make sure that your
                server has good power fallback facilities, like installing a
                UPS, and depending on how much availability is required,
                redundant power supplies may be called for. As well, users who
                have the resources may decide to invest in multiple disks for
                RAID support, and other options which may be needed in a High
                Availability environment. However, you certainly don't need
                them in all environments, and GNU/Linux's high quality means
                that in all but the most demanding environments, this won't be
                needed.
            </para>
        </sect1>
        <sect1>
            <title>LTSP Security</title>
            <para>
                Security has become a key challenge for administrators and
                LTSP both recognizes and handles this quite well. Often
                schools lack the specialized IT staff or time to lock and
                clean up computers.
            </para>
            <para>
                Operating systems with LTSP included, being Linux-based
                operating systems, enjoy the security advantages of its
                Unix-like and open source heritages. This translates into
                higher quality code and no spyware and viruses, like they
                plague other operating systems.
            </para>
            <para>
                In addition, it has a strict, proactive security policy
                which means that many common problems, such as open ports or
                misconfigured software, never make it into the released
                product. Finally, LTSP based systems are true multi-user
                operating systems, making it easy to allow users to complete
                their tasks without having a level of access that could
                compromise the system.
            </para>
        </sect1>
        <sect1>
            <title>LTSP Manageability</title>
            <para>
                With administrators and especially school IT departments
                deploying and administering an increasing number of computers,
                it is difficult to find time to manage individual machines.
                LTSP thin client technology, makes deployment and management
                simple and easy. A single server is all that is needed to set
                up, manage and administrate an entire network It is recognized
                that not every school's setup is the same, so LTSP (and the
                underlying operating system) has been made to easily customize
                your unique needs.
            </para>
        </sect1>
        <sect1>
            <title>It's Green!</title>
            <para>
                With the ongoing debate about climate change, questions are
                finally being asked and answered in the fields of IT,
                education and thin client technology in general. A recent
                study compared the energy and resource consumption of a
                regular PC and Thin Client setups. You can find that study
                here: <ulink url="http://it.umsicht.fraunhofer.de/TCecology/index_en.html">
                http://it.umsicht.fraunhofer.de/TCecology/index_en.html
                </ulink>
            </para>
            <para>
                They found that thin clients use half the energy of
                traditional workstations, which not only helps on the cost
                savings (calculate that a 40 terminal thin client lab will
                save approximately $500-$800 per year), but is ecologically
                effective in avoiding electronic waste and high carbon
                emissions. Thin client production, assembly and logistics
                costs far less and requires less energy than traditional PC
                manufacturing. The recycling of old machinery also helps the
                environment, making LTSP a green solution to the environmental
                and power saving issues many IT managers face today.
            </para>
        </sect1>
        <sect1>
            <title>Cost Effective </title>
            <para>
                With ever-increasing demands on school budgets, expensive
                technology is often last on the list. LTSP can help you offer
                what your students increasingly require from computer
                technology, without breaking the bank. GNU/Linux is and always
                will be free to acquire, use and modify, including the
                underlying LTSP structure that holds it all together.
            </para>
            <para>
                Need to set up another machine? Or another 100? Just install
                them! With GNU/Linux you'll have no more expensive OS upgrades
                and licenses, and having specialized programs on only some
                computers will become a thing of the past. When you build your
                network on Open Source software, you are freed to seek support
                for your computers from whomever you wish.
            </para>
            <para>
                GNU/Linux with LTSP can also help you save hardware costs, by
                allowing you to redeploy older machines as thin clients using
                LTSP technology. Whether you choose to set up many smaller
                labs with various LTSP servers or one giant setup with a load
                balanced LTSP setup (various servers working together to
                manage the users and applications logging on) the cost savings
                are always enormous.
            </para>
        </sect1>
        <sect1>
            <title>Well Supported</title>
            <para>
                LTSP support is available from the LTSP community. Many
                of the authors of the software included in LTSP, including the
                respective developers of the various LTSP GNU/Linux
                distribution implementations themselves, can be contacted
                directly via mailing lists and IRC channels.
            </para>
            <para>
                There are many forms of support available, including mailing
                lists, Wiki websites, IRC channels, and bug trackers. There
                are also special support groups for using LTSP and GNU/Linux.
            </para>
            <para>
                The official IRC support channel is found on freenode.org at
                #ltsp
            </para>
            <para>
                The official LTSP mailing list is found here:</para>
            <para>
                <ulink url="https://lists.sourceforge.net/lists/listinfo/ltsp-discuss">
                    https://lists.sourceforge.net/lists/listinfo/ltsp-discuss
                </ulink>
            </para>
            <para>
                In fact, some of the money that would have gone to
                purchasing software can instead be spent to hire local experts
                to help train you, and to help you support your network. LTSP
                can help you take more control over your network while also
                benefiting your local economy. With LTSP based systems, these
                choices are yours.
            </para>
        </sect1>
        <sect1>
            <title>Built for Education, Government and business</title>
            <para>
                LTSP based distros come with translations for many languages
                and localization features that allow people from all over the
                world to enjoy their computing experience. Accessibility
                features strive to provide a pleasant, high-quality computing
                experience to disabled users.
            </para>
            <para>
                The Free nature of GNU/Linux means that the applications a user
                is used to at their school or workplace is also available to
                them at home.  Users can install their favorite
                GNU/Linux distribution at home, and have all the same
                functionality they are used to.  In fact, many GNU/Linux
                distributions have Live CD's, which allow users to try, or even
                fully use the distribution at home, without even installing it
                on their home machine.
            </para>
            <para>
                The LTSP server software allows administrators, IT managers
                and teachers to create a low cost computer lab so that users
                can have access to the opportunities that GNU/Linux and the
                Internet can provide.
            </para>
            <para>
                Since setups can be adjusted to many situations, each thin
                client lab can be uniquely tailored to fit the business,
                agency or educational facility in question.
            </para>
        </sect1>
    </chapter>
    <chapter id='basic-concepts'>
        <title>Basic Concepts: Networks and Networking </title>
        <para>
            There are two components of a network: hardware and software.
            This section will give an introduction to both.
        </para>
        <sect1>
            <title>Hardware </title>
            <para>
                Networking works by breaking files and other data into
                little packets of information. These packets are transferred
                over a network. The difference between various types of
                networks is how they transfer packets.
            </para>
            <para>
                There are two types of networking hardware: wired and
                wireless.
            </para>
            <para>
                An important fact to remember is that a network will be only
                as fast as the slowest part. Making sure that your network
                setup matches your intended use case is an important
                consideration in an LTSP network.
            </para>
            <sect2>
                <title>Wired</title>
                <para>
                    Wired networking transfers packets over a cable that
                    resembles a telephone cord, but with more wires. Wired
                    networks can transfer packets at one of three possible
                    speeds: 10 Mbit/sec, 100 Mbit/sec, or (Gigabit) 1000
                    Mbit/sec.
                </para>
                <para>
                    A network is only useful if it can connect multiple
                    computers. There are some pieces of hardware that allow
                    multiple computers to be connected in a network. They look
                    alike, but they function differently and, likewise,
                    operate at different speeds.
                </para>
                <para><emphasis>Hub</emphasis></para>
                <para>
                    A hub is the simplest way to connect multiple computers.
                    A hub has a lot of ports in the front and usually has
                    several small lights corresponding to each port. The hub
                    takes a message it receives on one port and re-sends it to
                    all the ports. As a result, only one port can talk at a
                    time.
                </para>
                <para><emphasis>Switch</emphasis></para>
                <para>
                    A switch looks a lot like a hub; it has a lot of ports
                    in the front and usually has several small lights
                    corresponding to each port. However, a switch is unlike a
                    hub because it only makes a connection between the ports
                    it needs to. A switch can have multiple connections at the
                    same time. This allows a switch to be faster than a hub.
                </para>
                <para><emphasis>Router</emphasis></para>
                <para>
                    A router is used to make a connection between two
                    networks. Routers are also commonly used to connect a LAN
                    (local area network) to the Internet.
                </para>
            </sect2>
            <sect2>
                <title>Wireless</title>
                <para>
                    Some people may wish to try using LTSP in a wireless
                    environment, for various reasons.  This represents some
                    challenges.
                </para>
                <para>
                    Wireless networks typically have more latency than wired
                    networks, which generally makes interactive programs feel
                    slow and unresponsive.  As well, wireless adaptors cannot
                    directly PXE boot, as you need to set things such as ESSID,
                    keys, etc., which wouldn't be there in a PXE capable card.
                </para>
                <para>
                    However, for those wishing to use LTSP wirelessly, it is
                    still possible, but requires more hardware.  Wireless
                    bridge boxes are available, which contain both an ethernet
                    and a wireless network connection.  One can typically
                    connect to them like a small Internet router box, and
                    program them with the information pertinent to your
                    network.  You can then use a standard wired network card
                    connected directly to the bridge, and the bridge itself
                    will handle the wireless part.
                </para>
                <para>
                    This method has been used with success by users of LTSP in
                    the past.  The latency of wireless makes the experience
                    slower, however, depending on the application you wish to
                    use, you may find it acceptible.
                </para>
            </sect2>
        </sect1>
        <sect1>
            <title>Software</title>
            <para>
                The most common network infrastructure services include:
            </para>
            <itemizedlist>
                <listitem>
                    <para>
                        DHCP (Dynamic Host Configuration Protocol)</para>
                    <para>
                        Each computer on a network needs a unique identifier
                        called an IP address. The IP address allows packets to be
                        directed to the computer, much like a street address
                        allows mail to be delivered to the correct house. An IP
                        address follows a specific form: four groups of digits
                        forming a number from 0 to 255. For example, a local IP
                        address might be 192.168.2.50.
                    </para>
                    <para>
                        For convenience, a computer's IP address can be given
                        by a server running the Dynamic Host Configuration
                        Protocol (DHCP) service. DHCP automatically provides
                        network settings to the computers on the network. With
                        DHCP, there is no need to keep track of each computer's
                        IP address.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        DNS (Domain Name System)</para>
                    <para>
                        DNS is a service that runs on a server, and it is like a
                        phone book for computers, except that it stores IP
                        addresses instead of phone numbers. Your computer talks
                        to a DNS server every time you refer to another computer
                        system with a name instead of an IP address. For example:
                        www.ltsp.org, wikipedia.org, and google.com are all DNS
                        hostnames.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        NTP (Network Time Protocol)
                    </para>
                    <para>
                        NTP is a service that runs on a server and allows other
                        computers to synchronize their clocks. The server
                        synchronizes with an extremely accurate atomic clock, and
                        then the clients synchronize with the server.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Web Server
                    </para>
                    <para>
                        A Web server answers queries using protocols such as
                        HTTP, and sends content such as web pages back to clients.
                        Your Web browser almost exclusively talks to Web servers.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Web Proxy
                    </para>
                    <para>
                        A Web proxy is a service that runs on a server and
                        accesses Web sites on behalf of the clients. A proxy can
                        cache some data to allow faster repeated access to
                        commonly accessed pages. This is not really needed in
                        essence for ltsp thin clients, since nothing runs on them,
                        it all runs on the server. But in order to allow for
                        content filtering, a proxy is required. In the case of a
                        mixed network, where some clients are independent from the
                        the thin client network, a proxy server is useful. The
                        most common and recommended proxy solution is called
                        Squid, which can be easily installed through your distro's
                        package manager.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Content Filter or Net Guardian
                    </para>
                    <para>
                        A typical network requires a filtering policy to be
                        implemented, which can easily be done by software like
                        dansguardian, squidguard or squid-filter. This allows an
                        administrator to block and control unwanted traffic like:
                    </para>
                    <orderedlist>
                        <listitem>
                            <para>
                                banner ads,
                            </para>
                        </listitem>
                        <listitem>
                            <para>
                                user behaviour tracking via cookies,
                            </para>
                        </listitem>
                        <listitem>
                            <para>
                                animated pictures,
                            </para>
                        </listitem>
                        <listitem>
                            <para>
                                JavaScript, VBScript, ActiveX (dangerous as well
                                as annoying).
                            </para>
                        </listitem>
                    </orderedlist>
                </listitem>
                <listitem>
                    <para>
                        Firewall &amp; Port Blocker
                    </para>
                    <para>
                        A firewall is usually a service on the server, but often
                        DSL routers have the basic functionality of a firewall
                        too. A firewall can protect your server (and clients) by
                        restricting or allowing computers on the Internet from
                        initiating connections into your server or network. There
                        are many programs available for different distros. On
                        Ubuntu and Debian we recommend using gufw (uncomplicated
                        firewall), while Fedora has Fedora Firewall GUI, and SuSE
                        has Yast2 Firewall. If they are not already installed, you
                        can simply install them with your distro's package manager
                    </para>
                </listitem>
            </itemizedlist>
        </sect1>
        <sect1>
            <title>How LTSP Works</title>
            <orderedlist>
                <listitem>
                    <para>
                        LTSP is a collection of software that turns a normal
                        GNU/Linux installation into a terminal server. This allows
                        low-powered, low-cost thin-clients (or legacy hardware
                        you already own) to be used as terminals to the
                        thin-client server. LTSP is unique from other
                        thin-client systems in that it is considered by many
                        as the easiest to maintain. Other thin-client systems
                        require each client to have software that boots the
                        system to a point to be able to connect to the
                        terminal server. This could be a full-blown operating
                        system, or a minimal OS that simply provides an
                        interface to connect to the server. Systems such as
                        this generally require more maintenance and
                        administration, as the local software that boots the
                        thin-clients may become corrupt or contain bugs that
                        require attention. LTSP, on the other hand, requires
                        no client-side software. It requires only a PXE
                        capable network interface, which many thin-clients and
                        PCs have built-in already. This means that you need
                        absolutely no physical storage media (hard disk,
                        compact-flash, etc.) for your thin-client to boot to
                        LTSP. This significantly reduces the amount of
                        administration required to keep your network running.
                        The process of booting a thin-client to an LTSP server
                        is as follows:
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Thin-clients boot via a protocol called PXE
                        (Pre-eXecution Environment)
                    </para>
                </listitem>
                <listitem>
                    <para>
                        PXE requests an IP address from a local DHCP
                        server
                    </para>
                </listitem>
                <listitem>
                    <para>
                        The DHCP server passes additional parameters to
                        the thin-client and downloads a Linux initramfs filesystem image
                        via TFTP into a RAM disk on the client itself.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        The thin-client then boots the downloaded Linux
                        initramfs image, detects hardware, and connects to the LTSP
                        server's X session (normally handled by <link linkend="ldm">LDM</link>).
                    </para>
                </listitem>
            </orderedlist>
            <para>
                From here, all operations such as authenticating your
                username and password, launching applications, and viewing
                websites are actually handled on the LTSP server rather than
                the thin-client. The LTSP server transfers all graphical
                information to the thin-client over the network. This allows
                very low powered thin-clients to utilize the power of the
                server for all operations. It also allows for large client
                deployments with reduced overall resource utilization, as 50
                thin-clients all running the popular OpenOffice suite under
                different sessions generally only require enough RAM for a
                single instance of OpenOffice (excluding per-user
                configuration which is minimal). The server shares memory
                between user sessions, so libraries for applications are only
                loaded once and referenced for each user session.
            </para>
        </sect1>
    </chapter>
    <chapter id='tc-hardware'>
        <title>LTSP Thin Client hardware requirements</title>
        <para>
            A lot of LTSP deployments are in classroom environments, and
            usually, in these situations, the primary goal is to re-use
            existing hardware that the school already owns. However,
            specifically designed thin clients can be used also.
        </para>
        <sect1>
            <title>Hardware reuse and sizing</title>
            <para>
                A person setting up a LTSP thin client environment for the
                first time, typically asks two questions:
            </para>
            <orderedlist>
                <listitem>
                    <para>
                        Will my existing machines work as terminals, or,
                        what should I buy to use as a terminal?
                    </para>
                </listitem>
                <listitem>
                    <para>
                        How big a server do I need?
                    </para>
                </listitem>
            </orderedlist>
            <para>
                Chances are, hardware that you already have is more than
                sufficient for terminals. One of the great advantages of an
                LTSP Server is that you can set up a high quality lab of
                terminals for your students to use, by leveraging the machines
                you already have. As for servers, usually, it's very easy to
                turn any high-end single user desktop machine into a terminal
                server capable of handling many thin clients. We'll present
                some guidelines that should help in making the most of your
                resources.
            </para>
        </sect1>
        <sect1>
            <title>Clients</title>
            <sect2>
                <title>Older hardware</title>
                <para>
                    There are three things to consider when trying to re-use
                    existing hardware:
                </para>
                <orderedlist>
                    <listitem>
                        <para>
                            CPU
                        </para>
                    </listitem>
                    <listitem>
                        <para>
                            Network
                        </para>
                    </listitem>
                    <listitem>
                        <para>
                            Thin client memory
                        </para>
                    </listitem>
                    <listitem>
                        <para>
                            Video card
                        </para>
                    </listitem>
                </orderedlist>
            </sect2>
            <sect2>
                <title>CPU</title>
                <para>
                    For using the default, secure mode of LTSP, you'll need
                    to have a slightly faster CPU. Any 533 MHz or better CPU
                    should provide acceptable performance.
                </para>
                <para>
                    If you have slower clients, in the range of 233 MHz to
                    533 MHz, you may be able to use them, if you're willing to
                    reduce the security of your thin client network. More
                    information on this is available in the chapter on
                    <link linkend="ldm">LDM</link>.
                </para>
            </sect2>
            <sect2>
                <title>Network</title>
                <para>
                    A thin client boots over the network, using a small
                    program called a network boot loader. This network boot
                    loader is sometimes located on the card itself, or, for
                    older cards without one, the user can provide one on a
                    floppy or CDRom which can be used to boot the thin client.
                </para>
                <para>
                    Three common network boot loaders which can be used are:
                </para>
                <orderedlist>
                    <listitem>
                        <para>
                            <emphasis>PXE:</emphasis> This one is the most
                            common, and many network cards and motherboards
                            with built-in network cards support this. If you
                            have one of these, you'll be able to boot without
                            any problems.
                        </para>
                    </listitem>
                    <listitem>
                        <para>
                            <emphasis>Etherboot/gPXE:</emphasis> For older cards
                            that don't have PXE included on them, you can use
                            the Free Software equivalent, Etherboot, or it's
                            newer replacement, gPXE. This
                            excellent alternative to PXE can either be booted
                            from a floppy, memory stick, or CDRom, or, if
                            you're handy with electronics, be burned onto a
                            EPROM if your card has a socket for one. More
                            information on the project can be found at
                            http://www.etherboot.org, and you can download
                            ready-to-use Etherboot images at
                            http://www.rom-o-matic.org.
                        </para>
                    </listitem>
                    <listitem>
                        <para>
                            <emphasis>Yaboot:</emphasis> For Macintosh PowerPC
                            machines (iMac's and later), you can use the built
                            in Yaboot network boot.
                        </para>
                    </listitem>
                </orderedlist>
            </sect2>
            <sect2>
                <title>Thin client memory</title>
                <para>
                    The bare minimum for a thin client to work is about
                    48MB, but it will be unusably slow, so it is recommended
                    to install at least 128MB Ram, with 256MB Ram if you can
                    spare it. This will really help speed up thin clients.
                </para>
            </sect2>
            <sect2>
                <title>Video Card</title>
                <para>
                    Typically, any video card that uses the PCI bus and has
                    16 MB or more of memory, should make a reasonable client.
                </para>
            </sect2>
        </sect1>
    </chapter>
    <chapter id='server-hardware'>
        <title>LTSP Server requirements</title>
        <para>
            An LTSP thin client network is quite scalable; a moderately
            powerful machine can serve several thin clients, and if you need
            to add more thin clients, you can either expand the capabilities
            of the existing server, or, simply add more servers.
        </para>
        <sect1>
            <title>Recommended specs</title>
            <para>
                Server sizing in an LTSP network is more art than science.
                Ask any LTSP administrator how big a server you need to use,
                and you'll likely be told "It depends". How big a server you
                need does depend largely on what it is you're planning on
                doing with your thin client network. The server requirements
                needed for a network where the only use will be a little light
                web-browsing, with no Java or Flash, will be greatly different
                from a network where you want to do heavy graphics,
                interactive games, and Flash animation. Here are some common
                guidelines that should fit most "average" cases.
            </para>
            <sect2>
                <title>Memory</title>
                <para>
                    A GNU/Linux based operating system makes efficient use
                    of memory. The usual formula that's used for adding memory
                    to a thin client server is:
                </para>
                <para>
                    256 + (192 * users) MB
                </para>
                <para>
                    So, if your target is to have a server with 20
                    terminals, you'll need:
                </para>
                <para>
                    256 + (192 * 20) = 256 + 3840 = 4096 MB
                </para>
                <para>
                    So, you'll need 4 1 Gig memory sticks. Making sure
                    you've got enough memory is the single most important
                    thing you can do to help the performance of an LTSP thin
                    client server. If you do not have enough memory in your
                    server, you'll find your server will have to use the hard
                    drive as an overflow "virtual" memory. Hard drives are
                    much slower than memory, so you'll find things getting
                    very slow if this happens.
                </para>
                <para>
                    If you intend to make heavy use of graphics work in your
                    curriculum, you may want to add even more, perhaps
                    doubling the previous estimate.
                </para>
            </sect2>
            <sect2>
                <title>Processors</title>
                <para>
                    How fast a processor you need is entirely dependant on
                    what programs you plan to use. Interactive games require a
                    bit more than say, a word processor. If you plan to use
                    Java and Flash plug-ins in your web browser, these can
                    consume a lot of processing power. For a "mixed" model,
                    i.e. some people playing TuxMath, a few people browsing
                    the web, and a few people typing in OpenOffice.org, a 2GHz
                    or better processor should be able to adequately handle 20
                    people with some minor delays. A 3GHz processor would be
                    better.
                </para>
                <para>
                    For larger networks, moving to an SMP (Symmetric Multi
                    Processing), or multiple CPU server may be advantageous.
                    If you plan to handle 30 or more clients, a newer
                    dual-core Xeon server or dual-core Opteron will provide
                    good results.
                </para>
                <para>
                    Remember, if you need to serve a large number of
                    clients, it will be worth your while to configure multiple
                    LTSP servers, each handling some of the terminals.
                </para>
            </sect2>
            <sect2>
                <title>Disks</title>
                <para>
                    It's advisable to use some form of RAID in the terminal
                    servers. Besides saving your data when a single disks
                    fails, it improves the performance (especially read
                    performance, which is the most common type of file
                    access). For people on a budget, setting up software RAID
                    1, with 2 SATA disks with NCQ (Native Command Queueing)
                    will provide good results. If you have a bigger budget,
                    and a bigger network, setting up your server with RAID 10
                    along with 10,000 RPM western digital VelociRaptors will
                    give you the best speeds possible. This will provide you
                    with top notch performance and reliability.
                </para>
            </sect2>
        </sect1>
    </chapter>
    <chapter id='network'>
        <title>Network</title>
        <para>
            If you have more than 20 users, it is recommended to use Gigabit
            Ethernet connected to a gigabit port on a switch for your LTSP
            servers. Although normal usage ranges from 0.5 to 2mbit, clients
            can peak quite high (70mbit), especially when watching multimedia
            content.
        </para>
        <para>
            Booting a thin client involves several steps. Understanding what
            is happening along the way will make it much easier to solve
            problems, should they arise.
        </para>
        <para>
            There are four basic services required to boot an LTSP thin
            client. They are:
        </para>
        <orderedlist>
            <listitem>
                <para>
                    DHCP
                </para>
            </listitem>
            <listitem>
                <para>
                    TFTP
                </para>
            </listitem>
            <listitem>
                <para>
                    NFS or NBD
                </para>
            </listitem>
            <listitem>
                <para>
                    SSH
                </para>
            </listitem>
        </orderedlist>
    </chapter>
    <chapter id='chroot'>
        <title>The LTSP chroot environment</title>
        <para>
            In order to turn a computer into a thin client, we need to run a
            mini version of GNU/Linux on the workstation. It needs to boot
            this mini version of GNU/Linux over the network, since it probably
            won't have a hard drive on it's own. This mini GNU/Linux
            installation needs to live somewhere, and the best place for it is
            on the server.
        </para>
        <para>
            This scaled-down GNU/Linux installation, customized so that
            it's efficient to boot over the network, is called a chroot
            environment. You can have several of them, based upon several
            different CPU architectures.
        </para>
        <para>
            They'll normally live under <filename>/opt/ltsp</filename> on the server, with
            sub directories for each of the architectures. For instance, if you
            have a lab full of old Power PC Macs, and older PC's, you'll
            have an <filename>/opt/ltsp/ppc</filename> and an
            <filename>/opt/ltsp/i386</filename> directory on the
            server.
        </para>
        <para>
            This is the LTSP project's preferred area to store the chroot,
            however, different distros that support LTSP are free to change
            this.  Check with your distro's specific LTSP documentation to see
            where the LTSP chroot is stored.
        </para>
        <para>
            The reason why it is called a chroot environment is that to
            install it, the GNU/Linux command chroot is called to actually set
            the installation root to
            <filename>/opt/ltsp/&lt;arch&gt;</filename>. From there, a
            scaled-down version of the distribution is installed. What this
            means is that for you to manage the chroot, performing such things
            as updates, all you need to do is use the chroot command to change
            the root of your installation. Then you can use all your tools
            like you normally would.
        </para>
        <sect1>
            <title>The boot process of a thin client</title>
            <orderedlist>
                <listitem>
                    <para>
                        Load the Linux kernel into the memory of the thin
                        client. This can be done several different ways,
                        including:
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Each of the above booting methods will be explained
                        later in this chapter. But for now, it should be noted
                        that it makes sense in almost all cases to use a PXE
                        based network card during booting  for the fastest,
                        and easiest to setup method.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Once the kernel has been loaded into memory, it will
                        begin executing.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        The kernel will initialize the entire system and all
                        of the peripherals that it recognizes.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        This is where the fun really begins. During the
                        kernel loading process, an initramfs image will also
                        be loaded into memory.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Normally, when the kernel is finished booting, it will
                        launch the new task launcher <command>upstart</command>,
                        which will handle starting up a server or workstation.
                        But, in this case, we've instructed the kernel to load
                        a small shell script instead. This shell script is
                        called <command>/init</command>,and lives in the root
                        of the initramfs.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        The <command>/init</command> script begins by mounting
                        <filename>/proc</filename> and
                        <filename>/sys</filename>, starts <command>udev</command> to
                        discover and initialize hardware, especially the
                        network card, which is needed for every aspect of the
                        boot from here on. As well, it creates a small ram
                        disk, where any local storage that is needed (to
                        configure the <filename>xorg.conf</filename> file, for
                        instance) can be written to.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        The <emphasis>loopback</emphasis> network interface is
                        configured. This is the networking interface that has
                        <emphasis>127.0.0.1</emphasis> as its IP address.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        A small DHCP client called <command>ipconfig</command>
                        will then be run, to make another query from the DHCP
                        server. This separate user-space query gets
                        information supplied in the dhcpd.conf file, like the
                        nfs root server, default gateway, and other important
                        parameters.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        When <command>ipconfig</command> gets a reply from the
                        server, the information it receives is used to
                        configure the Ethernet interface, and determine the
                        server to mount the root from.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Up to this point, the root filesystem has been a ram
                        disk. Now, the <command>/init</command> script will
                        mount a new root filesystem via either NBD or NFS. In
                        the case of NBD, the image that is normally loaded is
                        <filename>/opt/ltsp/images/&lt;arch&gt;.img</filename>.
                        If the root is mounted via NFS, then the directory
                        that is exported from the server is typically
                        <filename>/opt/ltsp/&lt;arch&gt;</filename>.
                        It can't just mount the new filesystem as
                        <filename>/</filename>. It must
                        first mount it to a separate directory. Then, it will
                        do a <command>run-init</command>, which will swap the
                        current root filesystem for a new filesystem. When it
                        completes, the filesystem will be mounted on
                        <filename>/</filename>. At
                        this point, any directories that need to be writable
                        for regular start up to occur, like
                        <filename>/tmp</filename>, or <filename>/var</filename>, are
                        mounted at this time.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Once the mounting of the new root filesystem is
                        complete, we are done with the <command>/init</command> shell script and
                        we need to invoke the real <command>/sbin/init</command> program.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        The <command>init</command> program will read the
                        <filename>/etc/event.d</filename>
                        directory and begin setting up the thin client
                        environment. From there, upstart will begin reading
                        the start up commands in <filename>/etc/rcS.d</filename>.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        It will execute the <command>ltsp-client-setup</command> command
                        which will configure many aspects of the thin client environment,
                        such as checking if local devices need starting, loading any
                        specified modules, etc.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Next, the <command>init</command> program will begin
                        to execute commands in the <filename>/etc/rc2.d</filename> directory
                    </para>
                </listitem>
                <listitem>
                    <para>
                        One of the items in the <filename>/etc/rc2.d</filename>
                        directory is the <command>ltsp-client-core</command>
                        command that will be run while the thin client is
                        booting.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        The &lts.conf; file will be parsed,
                        and all of the parameters in that file that pertain to
                        this thin client will be set as environment variables
                        for the <command>ltsp-client-core</command> script
                        to use.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        If Sound is configured at this point, the
                        <command>pulseaudio</command>
                        daemon is started, to allow remote audio connections
                        from the server to connect and play on the thin
                        client.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        If the thin client has local device support enabled,
                        the <command>ltspfsd</command> program is started to
                        allow the server to read from devices such as memory
                        sticks or CD-Roms attached to the thin client.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        At this point, any of the screen sessions you've
                        defined in your &lts.conf; will be
                        executed.
                    </para>
                    <para>
                        Screen sessions are what you want to launch on all
                        of the virtual screens on your terminal. These are the
                        standard virtual screens that all GNU/Linux
                        distributions usually have, i.e.
                        <keycombo><keycap>Alt</keycap><keycap>F1</keycap></keycombo>, through
                        <keycombo><keycap>Alt</keycap><keycap>F10</keycap></keycombo>.
                    </para>
                    <para>
                        By default, a standard character based getty will be
                        run on screen 1 (<varname>SCREEN_01</varname> in the &lts.conf; file).
                    </para>
                    <para>
                        As well, if nothing else is specified in the
                        &lts.conf;
                        file, an &ldm; screen script is run
                        on <varname>SCREEN_07</varname>. The LTSP Display
                        Manager (&ldm;)
                        is the default login manager for LTSP.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        If <varname>SCREEN_07</varname> is set to a value of
                        &ldm;, or <command>startx</command>, then the X
                        Windows System will be launched, giving you a graphical user interface.
                    </para>
                    <para>
                        By default, the Xorg server will auto-probe the card,
                        create a default <filename>/etc/X11/xorg.conf</filename> file on the
                        ram-disk in the terminal, and start up xorg with that custom config.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        The X server will either start an encrypted <command>ssh</command>
                        tunnel to the server, in the case of &ldm;, or an an
                        XDMCP query to the LTSP server, in the case of
                        <command>startx</command>. Either way,
                        a login box will appear on the terminal.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        At this point, the user can log in. They'll get a
                        session on the server.
                    </para>
                    <para>
                        This confuses a lot of people at first. They are
                        sitting at a thin client, but they are running a
                        session on the server. All commands they run will be
                        run on the server, but the output will be displayed on
                        the thin client.
                    </para>
                </listitem>
            </orderedlist>
        </sect1>
    </chapter>
    <chapter id='network-boot'>
        <title>Network booting the thin client</title>
        <para>
            Getting the thin client to boot over the network can be
            accomplished in a variety of ways:
        </para>
        <orderedlist>
            <listitem>
                <para>
                    Boot ROM
                </para>
            </listitem>
            <listitem>
                <para>
                    Local media
                </para>
            </listitem>
        </orderedlist>
        <sect1>
            <title>Boot ROM</title>
            <para>
                Depending on your network card, it may already contain a
                boot ROM, or you may be able to use an EPROM programmer to
                create your own. Check the hardware documentation for the
                network card in your thin client for details.
            </para>
            <sect2>
                <title>Etherboot</title>
                <para>
                    Etherboot is a very popular open-source bootrom project.
                    It contains drivers for many common network cards, and
                    works very well with LTSP.
                </para>
                <para>
                    ROM images suitable for booting from floppy, CD-ROM,
                    etc., can be obtained from http://www.rom-o-matic.org
                </para>
                <para>
                    Linux kernels must be tagged with the <command>mknbi-linux</command>,
                    which will prepare the kernel for network booting, by
                    prefixing the kernel with some additional code, and
                    appending the initrd to the end of the kernel.
                </para>
                <para>
                    The kernels that are supplied with LTSP are already
                    tagged, and ready to boot with Etherboot.
                </para>
            </sect2>
            <sect2>
                <title>PXE</title>
                <para>
                    Part of the 'Wired for Management' specification from the
                    late 1990's included a specification for a bootrom
                    technology known as the
                    <emphasis>Pre-boot Execution Environment</emphasis>
                    commonly abbreviated as <emphasis>PXE</emphasis>.
                </para>
                <para>
                    A PXE bootrom can load at most a 32 kilo-byte file. A
                    Linux kernel is quite a bit larger than that. Therefore,
                    we setup PXE to load a 2nd stage boot loader called
                    <command>pxelinux</command>, which is small enough
                    to be loaded. It knows how to load
                    much larger files, such as a Linux kernel.
                </para>
            </sect2>
        </sect1>
        <sect1>
            <title>Local media</title>
            <para>
                If your network card in the thin client doesn't have a boot
                ROM built in, and you don't have access to an EPROM burner,
                have no fear! Chances are, that old machine has a floppy
                drive, or CD-ROM in it. If so, then you can use local media to
                boot the thin client.
            </para>
            <sect2>
                <title>Floppy disk</title>
                <para>
                    Booting Etherboot from a floppy is an excellent way of
                    booting an LTSP thin client that doesn't have a boot ROM.
                    Etherboot is loaded in the boot sector of the floppy.
                    Then, it will act just like a bootrom. The boot code will
                    be executed, the network card will be initialized, and the
                    kernel will be loaded from the network server.
                </para>
            </sect2>
            <sect2>
                <title>Hard disk</title>
                <para>
                    The hard disk can be used with LILO or GRUB, to load the
                    Linux kernel and initrd. You can also load the Etherboot
                    bootrom image from the hard disk, and it will act like a
                    bootrom.
                </para>
            </sect2>
            <sect2>
                <title>CD-ROM</title>
                <para>
                    A bootable CD-ROM can be loaded either with a Linux
                    kernel, or an Etherboot image.
                </para>
            </sect2>
            <sect2>
                <title>USB Memory device</title>
                <para>
                    Just like a CD-ROM, Floppy disk and Hard disk, you can
                    use a USB Memory device to boot an Etherboot module.
                </para>
            </sect2>
        </sect1>
        <sect1>
            <title>Installation</title>
            <para>
                With the integration of LTSP into distributions, installation
                of LTSP is now usually as easy as adding the LTSP packages in
                your distro's package manager.  Consult your distribution's
                documentation for details on how to install LTSP on your
                particular system.
            </para>
            <para>
                However, as a general guideline, usually after you've installed
                your distributions' LTSP packages, and configured your network
                interfaces, and some kind of DHCP3 server, you'd run (as root):
            </para>
            <screen>
sudo ltsp-build-client
            </screen>
            <para>
                If you are on a 64-bit system but your clients
                have another architecture use the --arch option
                e.g. <screen>ltsp-build-client --arch i386</screen>
            </para>
            <para>
                After that, you should be able to boot your first thin
                client.
            </para>
        </sect1>
    </chapter>
    <chapter id='customizing-ltsconf'>
        <title>Customizing thin client behaviour</title>
        <para>
            By default, most thin clients will automatically configure
            themselves correctly, and just work when they're plugged in.
            However, sometimes you may wish to customize their behaviour. You
            would do this by editing the &lts.conf; file.
        </para>
        <sect1>
            <title>Location of the lts.conf file</title>
            <para>
                In order to speed up LTSP, by default, we're using NBD
                (Network Block Devices) rather than NFS. To do this, we'd had
                to move the the lts.conf file out of the chroot and into the
                TFTP directory, in /var/lib/tftpboot/ltsp/&lt;arch&gt;, where
                &lt;arch&gt; is the architecture you are working on (usually i386,
                but could be something else, like amd64 for example). This
                means you can make changes to the file immediately, and simply
                reboot the terminal, without recompiling the image.
            </para>
        </sect1>
        <sect1>
            <title>Sample lts.conf file</title>
            <para>
                Here is an example of the lts.conf file: </para>
            <screen>
################
# Global defaults for all clients
# if you refer to the local server, just use the
# "server" keyword as value
# see lts_parameters.txt for valid values
################

[default]
    X_COLOR_DEPTH=16
    LOCALDEV=True
    SOUND=True
    NBD_SWAP=True
    SYSLOG_HOST=server
    XKBLAYOUT=de

################
#[MAC ADDRESS]: Per thin client settings
################

[00:11:25:84:CE:BA]
    XSERVER = vesa
    X_MOUSE_DEVICE=/dev/ttyS0
    X_MOUSE_PROTOCOL=intellimouse

###############
# A Thin Client Print server
# (switch off X by pointing tty7 to shell,
# to save resources)
###############

[00:11:25:93:CF:00]
    PRINTER_0_DEVICE=/dev/usblp0
    SCREEN_07=shell

###############
# A workstation that executes a specific
# command after login
###############

[00:11:25:93:CF:02]
    LDM_SESSION=/usr/bin/myloginscript
            </screen>
        </sect1>
    </chapter>
    <chapter id='lts-conf'>
        <title>Format of the lts.conf file</title>
        <para>
            When LTSP was designed, one of the issues that needed to be
            dealt with was varying hardware configurations for the thin
            client. Certainly, whatever combination of processor, network card
            and video card available today would not be available in 3 months,
            when you want to add more thin clients to the network. So, LTSP
            devised a way of specifying the configuration of each thin client.
            The configuration file is called lts.conf and it lives in the
            <filename>/var/lib/tftpboot/ltsp/&lt;arch&gt;/</filename> directory.
        </para>
        <para>
            The format of the lts.conf allows for 'default' settings and
            individual thin client settings. If all of your thin clients are
            identical, you could specify all of the configuration settings in
            the <varname>'[Default]'</varname> section. The file must have a first line
            containing <varname>'[Default]'</varname> in any case.
        </para>
        <sect1>
            <title>Section headings </title>
            <para>
                Section headings begin with an identifier in the form
                [Default] which is used for all computers as mentioned above,
                and [MAC address] for individual workstations, in the form of
                [XX:XX:XX:XX:XX:XX], where X is the digits 0-9, or A-F.
            </para>
            <para>
                You can usually read the MAC address for a network card from
                a sticker on the card itself, or use some kind of network tool
                to discover it. The best way to check for the MAC address of
                the machine is by starting it up, checking its IP number and
                doing a <command>arp -an</command> on the server, this should then tell you
                which IP number has which MAC address.
            </para>
        </sect1>
        <sect1>
            <title>Variable Assignments</title>
            <para>
                After the section heading, you can then define variables.
                Variables are ether boolean values, requiring a True/False or
                Y/N answer. Note that you can either use True or False, Yes or
                No, or Y or N. Whichever you prefer. Other variables may
                simply be strings, supplied after the = sign. The general
                format of an assignment looks like:
            </para>
            <screen>
VARIABLE = value
            </screen>
            <para>
                Comments can be inserted into the file for your
                documentation purposes. Comments start with a # character, and
                everything after the # for the rest of the line is considered
                a comment.
            </para>
        </sect1>
        <sect1>
            <title>The LIKE keyword</title>
            <para>
                The <varname>LIKE</varname> keyword allows you to define a
                general set of parameters under a unique identifier, and then
                assign individual workstations that set of parameters using the
                <varname>LIKE</varname> keyword.  An example will illustrate
                it's use.
            </para>
            <para>Let's assume you have 3 kinds of thin clients on your
                network.  One set, which are used in the lab, have older video
                cards, and must use 16 bit colour at 1024x768 resolution.
                Another set need to have their video ram set to 8 megs, and a
                third set which auto-detect everything correctly.  We don't
                need to specify anything for the third set, but having some
                symbolic names for the first two would help us to maintain the
                &lts.conf; file.
            </para>
            <para>
                Here's an example &lts.conf; that
                illustrates how this would be done:
            </para>
            <screen>
[Lab]
    X_COLOR_DEPTH = 16
    X_MODE_0 = 1024x768

[Lowram]
    X_VIDEO_RAM = 8096

[00:40:32:71:77:A1]
    LIKE = Lab

[00:70:84:BB:27:52]
    LIKE = Lowram
            </screen>
            <para>
                As you can see, using the <varname>LIKE</varname> keyword can
                make your &lts.conf; more readable, by
                allowing you to group related parameters together into a single
                symbolic name.
            </para>
        </sect1>
    </chapter>
    <chapter id='general-parms'>
        <title>General thin client parameters</title>
        <para>
            There are several variables that one can define in the lts.conf
            file which control how the thin client interacts with the server.
            These are:
        </para>
        <xi:include
         href='lts.conf.xml'
         xpointer='lts-conf-general-list'
         xmlns:xi='http://www.w3.org/2001/XInclude' />
    </chapter>
    <chapter id='localdev-parms'>
        <title>Local Device thin client parameters</title>
        <para>
            Local devices such as USB sticks, CD-ROM drives, or even floppy
            disks need special configuration in order to be accessed from the
            thin client. The following values allow to enable or disable the
            use of various local devices:
        </para>
        <xi:include
         href='lts.conf.xml'
         xpointer='lts-conf-localdev-list'
         xmlns:xi='http://www.w3.org/2001/XInclude' />
    </chapter>
    <chapter id='screen-scripts'>
        <title>Screen Scripts</title>
        <para>
            Screen scripts are how LTSP determines what type of login will
            run on what virtual screen. Most GNU/Linux machines have 12
            virtual consoles, which you can access by pressing
            <keycombo><keycap>Control</keycap><keycap>Alt</keycap><keycap>F1</keycap></keycombo>, through
            <keycombo><keycap>Control</keycap><keycap>Alt</keycap><keycap>F12</keycap></keycombo>.
            On some distributions there is a text based getty that is
            started on screen 1, but you normally can't log into it, as there
            are no local users on the thin client.
        </para>
        <para>
            However, for debugging purposes, you may want to set up root to
            log in on the thin client. You may need to do this if you're
            debugging problems with local devices, for example. Fortunately,
            it's easy to do: on the server, as root, just chroot into the LTSP chroot,
            and set the password with passwd.
        </para>
        <screen>
chroot /opt/ltsp/&lt;arch&gt;
passwd
        </screen>
        <para>
            By default, if there's nothing else mentioned in
            &lts.conf;,
            an LDM session will be started on screen 7.
        </para>
        <xi:include
         href='lts.conf.xml'
         xpointer='lts-conf-screen-list'
         xmlns:xi='http://www.w3.org/2001/XInclude' />
    </chapter>
    <chapter id='rdesktop'>
        <title>The "rdesktop" screen script</title>
        <para>
            LTSP includes an &rdesktop; screen script that
            can be used to bring up a full screen RDP connection using
            &rdesktop; on the thin client. This
            screen script can be invoked in one of two ways.
        </para>
        <sect1>
            <title>Single Line</title>
            <para>
                For example, by adding the following
                &lts.conf; parameter:
            </para>
            <screen>
SCREEN_07 = "rdesktop -a 16 192.168.0.253"
            </screen>
            <para>
                That is, calling it with the arguments you normally would on the
                command line. This method of invocation is useful in that you can have
                multiple screens pointing to different RDP servers with different
                arguments and switch between them.
            </para>
        </sect1>
        <sect1>
            <title>Multiple Line</title>
            <para>
                For example, by adding the following parameters to
                &lts.conf;:
            </para>
            <screen>
SCREEN_07 = rdesktop
RDP_SERVER = 192.168.0.253
RDP_OPTIONS = "-a 16"
            </screen>
            <para>
                This method will apply the same arguments and server to all screens.
            </para>
        </sect1>
        <sect1>
            <title>RDP + Local Devices</title>
            <para>
                When you run an &rdesktop; screen script,
                &rdesktop; runs on the thin
                client. The thin client, by default, has no way of automounting
                removable devices, and the normal localdev approach used in an
                &ldm; session in which local devices invoke a call over ssh to have the
                Linux server mount the device obviously won't work.
            </para>
            <para>
                To address this issue in a controlled way, we have chosen to use
                &ltspfs; as a local automounter for RDP
                sessions. To add local device support, you must:
            </para>
            <orderedlist>
                <listitem>
                    <para>
                        Install ltspfs in the chroot.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Use folder redirection in &rdesktop; to map the local /media/root
                        folder created by ltspfs to the server as a shared drive.  For
                        example, you could add the following &rdesktop; argument:
                    </para>
                    <screen>
-r disk:Drives=/media/root
                    </screen>
                    <para>
                        With this redirection, you should get a "Drives" share in Windows
                        under My Computer. Inside the "Drives" share, a folder will appear for
                        each local device.  The local device will be mounted with ltspfs, so
                        they can just be removed when the device is not being written to
                        without "unmounting".
                    </para>
                </listitem>
            </orderedlist>
        </sect1>
        <sect1>
            <title>RDP + Local Sound</title>
            <para>
                You should be able to add sound to your RDP session with the following
                &rdesktop; argument:
            </para>
            <screen>
-r sound:local
            </screen>
        </sect1>
    </chapter>
    <chapter id='modules-scripts'>
        <title>Modules and startup scripts</title>
        <para>
            For the most part, LTSP does a very good job of detecting what
            hardware's on your thin client. However, it's possible that you
            may want to manually specify a kernel module to load after boot.
            Alternatively, you may have a script you've written that you've
            put in the chroot, and want to make sure gets run at startup. LTSP
            provides some hooks to allow you to do this.
        </para>
        <xi:include
         href='lts.conf.xml'
         xpointer='lts-conf-modules-list'
         xmlns:xi='http://www.w3.org/2001/XInclude' />
    </chapter>
    <chapter id='sound'>
        <title>Sound in LTSP</title>
        <para>
            Sound in LTSP is handled by running the
            <command>pulseaudio</command> daemon on the
            thin client, which sits on top of the ALSA kernel drivers.  The
            thin client's kernel should detect the thin client sound hardware
            via the usual udev mechanisms, and enable the sound card.  At boot
            time, the <command>pulseaudio</command> daemon is run, which allows the thin client to
            receive audio streams via network connections.
        </para>
        <para>
            On login, the LDM sets both the <varname>PULSE_SERVER</varname> and
            <varname>ESPEAKER</varname>
            environment variables for the X windows session, to allow the
            server to re-route the sound over a TCP/IP socket to the thin
            client.
        </para>
        <xi:include
         href='lts.conf.xml'
         xpointer='lts-conf-sound-list'
         xmlns:xi='http://www.w3.org/2001/XInclude' />
    </chapter>
    <chapter id='xwin-parms'>
        <title>X-Windows parameters</title>
        <para>
            Setting up X windows on the thin client's normally a pretty easy
            operation. The thin client uses X.org's own auto configuration
            mode to let X determine what it thinks is installed in the box.
        </para>
        <para>
            However, sometimes, this doesn't always work. Either due to
            strange/buggy hardware, or buggy drivers in X.org, or because X
            detects default settings that you don't want. For instance, it may
            detect that your monitor is capable of doing 1280x1024, but you'd
            prefer it to come up in 1024x768 resolution. Fortunately, you can
            tweak individual X settings, or, alternatively, simply provide
            your own <filename>xorg.conf</filename> to use.
        </para>
        <sect1>
            <title>X.org Configuration</title>
            <xi:include
             href='lts.conf.xml'
             xpointer='lts-conf-xorg-list'
             xmlns:xi='http://www.w3.org/2001/XInclude' />
        </sect1>
    </chapter>
    <chapter id='xrandr'>
        <title>XRANDR setting for managing displays</title>
        <para>
            The new Xorg Xserver has the ability to figure out (for the most part,
            to the extent that the driver helps in the process) the best mode for
            the videocard.  Moreover, with the new dependency upon hal and Xrandr,
            it is recommended to add input devices with hal and modify video modes
            with Xrandr 1.2 calls.  In essence, the xorg.conf becomes a place really
            to fix deficiencies in poorly written drivers or to force certain
            abnormal driver behavior in a particular environment in a way that can
            not be otherwise done through hal or Xrandr.
        </para>
        <sect1>
            <title>New Xorg structure within LTSP</title>
            <para>
                To accommodate this, Xorg now understands partial xorg.conf files.
                Meaning you only add the sections that you need to force.  Otherwise, it
                discovers everything.  That's why you might see minimalist xorg.conf
                files in your LTSP chroot.
            </para>
            <para>
                The <filename>screen-session.d/</filename> directory (located in the
                chroot's <filename>/usr/share/ltsp directory</filename>) is a structure of shell scripts all
                of which are sourced in order (similar to
                <filename>Xsession.d/</filename> or <filename>rc.d/</filename> that you
                may be familiar with).  These scripts are executed upon the beginning of
                each session but before the Xserver (if the session runs an Xserver) is
                launched.  You can make whatever script you want that may need to run at
                that point.  For LTSP, one thing we use it for is to set up
                <emphasis>how</emphasis> the
                Xserver will be launched.  This entails not just generating a
                <filename>xorg.conf</filename>
                file as needed, but also configuring the parameters that the Xserver
                should be launched with.  The nice thing about a collection of sourced
                scripts is that it gives flexibility to the distribution or to the
                administrator to add additional scripts that may be required for that
                distribution or for a particular network environment that will not
                modify existing files (and therefore require more maintenance to care
                for updates in the upstream code).
            </para>
        </sect1>
        <sect1>
            <title>Script structure</title>
            <para>
                Each script is named with a prefix letter, then an order number, then a
                name.  The prefix letter determines when the scripts of that prefix are
                executed and the order number determines in what order.
            </para>
            <para>
                PREFIXES:
                Prefixes that may be used include:
            </para>
            <para>
                S - Is a script that runs at the beginning of a session (screen script)
                K - Is a script that runs at the end of a session (screen script)
                XS - Is a script that is only run at the beginning of screen scripts
                that run an Xserver
            </para>
            <para>
                All of the scripts that generate a xorg.conf or modify the Xserver
                arguments are XS* scripts.
            </para>
            <para>
                These scripts are mostly organized by the particular lts.conf parameter
                or function that they affect.  For example, XS85-xvideoram adds the
                ability to specify the X_VIDEO_RAM parameter in lts.conf and force the
                amount of video ram used by the driver.
            </para>
            <para>
                If you are going to create your own script, I recommend looking at other
                scripts to understand the structure.  Since many hacks may impact the
                same xorg.conf sections, each section has a function of hacks assigned
                to it, and in your script, you would create a function and add it to the
                list of functions for that section.  For example, if you add something
                to the Monitor section (that cannot already be added through existing
                functions) you would create a function in your script and add it to the
                monitor_hacks function list.  Again, easier to read the code and look at
                examples to understand how to write a new script.
            </para>
            <para>
                Also, please note that one of the lts.conf parameters you can specify
                is:  <varname>CONFIGURE_X_COMMAND</varname>
                This should be set to a path to a script.  So, if you have the old
                configure-x.sh and like it better, simply copy it into the chroot, to
                say,
                <command>/opt/ltsp/&lt;arch&gt;/usr/share/ltsp/configure-x.sh</command>
                and then in &lts.conf;,
                specify:  <screen>CONFIGURE_X_COMMAND =
                    "/usr/share/ltsp/configure-x.sh"</screen>  and
                you will be back to where you were.
            </para>
        </sect1>
        <sect1>
            <title>XRandR parameters</title>
            <xi:include
             href='lts.conf.xml'
             xpointer='lts-conf-xrandr-list'
             xmlns:xi='http://www.w3.org/2001/XInclude' />
        </sect1>
    </chapter>
    <chapter id='printer'>
        <title>Printer configuration parameters</title>
        <para>
            Sometimes, it's convenient to hang a printer off of a thin
            client in a lab, so that the computer lab has access to local
            printing resources. Fortunately, LTSP can accommodate printing on
            the workstation.
        </para>
        <para>
            LTSP can connect up to 3 printers per workstation to the network
            via a small daemon called JetPipe. Both parallel and USB printers
            are supported. JetPipe makes the printer look like a standard HP
            Jet Direct printer interface. You can then create any cups printer
            on your server, and point it at the printer via a Jet Direct
            connection.
        </para>
        <para>
            In your <filename>dhcpd.conf</filename> file that controls your
            thin client IP assignments, you'll want to assign a static IP for
            the terminal with the printers, to guarantee that it gets the same
            IP address every time it boots. Otherwise, your printing won't
            work if the terminal leases a different IP address.
        </para>
        <xi:include
         href='lts.conf.xml'
         xpointer='lts-conf-printer-list'
         xmlns:xi='http://www.w3.org/2001/XInclude' />
    </chapter>
    <chapter id='keyboard'>
        <title>Keyboard parameters</title>
        <para>
            All of the keyboard support files are copied into the
            <filename>/opt/ltsp/&lt;arch&gt;</filename> hierarchy, so configuring international keyboard
            support is simply a matter of configuring X.org. There are several
            configuration parameters for this.
        </para>
        <para>
            The values for the above parameters are from the X.org
            documentation. Whatever is valid for X.org is valid for these
            parameters.
        </para>
        <para>
            We would like to add documentation to show what values are
            needed for each type of international keyboard. If you work with
            this and can configure your international keyboards, feedback to
            LTSP would be greatly appreciated.
        </para>
        <xi:include
         href='lts.conf.xml'
         xpointer='lts-conf-keyboard-list'
         xmlns:xi='http://www.w3.org/2001/XInclude' />
    </chapter>
    <chapter id='touchscreen'>
        <title>Touchscreen configuration</title>
        <para>
            Description to be added later.
        </para>
        <xi:include
         href='lts.conf.xml'
         xpointer='lts-conf-touchscreen-list'
         xmlns:xi='http://www.w3.org/2001/XInclude' />
    </chapter>
    <chapter id='localapps'>
        <title>Local Applications</title>
        <para>
            Description to be added later.
        </para>
        <xi:include
         href='lts.conf.xml'
         xpointer='lts-conf-localapps-list'
         xmlns:xi='http://www.w3.org/2001/XInclude' />
    </chapter>
    <chapter id='ldm'>
        <title>The LDM display manager</title>
        <sect1>
            <title>Introduction</title>
            <para>
                The LTSP Display Manager, or &ldm; is the
                display manager specifically written by the LTSP project to
                handle logins to a GNU/Linux server. It is the default display
                manager for LTSP thin clients running under LTSP, and has a
                lot of useful features:
            </para>
            <orderedlist>
                <listitem>
                    <para>
                        It is written in C, for speed and efficiency on low
                        end clients.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        It supports logging in via either a greeter (a
                        graphical login application) or autologin.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        It can be configured to encrypt X Windows traffic,
                        for increased security, or leave it unencrypted, for
                        better performance on slower clients.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        It contains a simple load-balancing system, to allow
                        the system administrator to allow load balancing
                        across several servers.
                    </para>
                </listitem>
            </orderedlist>
            <para>
                We'll go over the &lts.conf; entries you'll
                need to control these features below.
            </para>
        </sect1>
        <sect1>
            <title>Theory of operation</title>
            <para>
                To help understand the following sections, a bit of an
                explanation of how &ldm; does it's work is
                needed. Most thin client display managers tend to run up on
                the server. The &ldm; display manager is
                unique in that it runs on the thin client itself. This allows
                the thin client to have a lot of choice as to how it will set
                up the connection. A typical login session goes as follows:
            </para>
            <orderedlist>
                <listitem>
                    <para>
                        &ldm; launches and starts up the X
                        Windows display on the thin client.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        &ldm; starts up the greeter, which is
                        a graphical program which presents the user with a
                        nice login display and allows them to select their
                        session, language, and host they'd like to log into.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        &ldm; collects the information from
                        the greeter, and starts an ssh session with the
                        server. This ssh connection is used to create an ssh
                        master socket, which is used by all subsequent
                        operations.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Now, the users selected session is started via the
                        master socket. Depending on whether or not an
                        encrypted connection has been requested, via the
                        <varname>LDM_DIRECTX</varname> parameter, the session is either connected
                        back to the local display via the ssh tunnel, or via a
                        regular TCP/IP connection.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        During the session, any memory sticks, or other
                        local devices that are plugged in, communicate their
                        status to the server via the ssh control socket.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        When the user exits the session, the ssh connection is
                        closed down, the X server is stopped, and &ldm;
                        restarts itself, so everything starts with a clean slate.
                    </para>
                </listitem>
            </orderedlist>
        </sect1>
        <sect1>
            <title>Encrypted versus unencrypted sessions</title>
            <para>
                By default, LTSP5 encrypts the X session between the server.
                This makes your session more secure, but at the cost of
                increased processing power required on the thin client and on
                the server. If processing power is a concern to you, it's very
                easy to specify that the connection for either an individual
                workstation, or the default setting should use an unencrypted
                connection. To do so, simply specify:
            </para>
            <screen>
LDM_DIRECTX = True
            </screen>
            <para>
                in your &lts.conf; file in the appropriate
                section.
            </para>
        </sect1>
        <sect1>
            <title>Auto login features</title>
            <para>
                This new version of LDM supports auto login of accounts, if
                specified in the &lts.conf; file. Simply
                create a config section for each of the terminals you want to
                log in automatically (you can use either MAC address, IP
                address, or hostname) and specify the variable
                <varname>LDM_USERNAME</varname>
                and <varname>LDM_PASSWORD</varname>. Note that you must have
                created these accounts on the server, with the passwords
                specified. An example will serve to illustrate how to use
                this:
            </para>
        </sect1>
        <sect1>
            <title>Load balancing features</title>
            <para>
                In this version of LTSP, there's a simple load-balancing
                solution implemented that allows administrators to have
                multiple LTSP servers on the network, and allow the thin
                client to pick which one of the servers it would like to log
                into.
            </para>
            <para>
                The host selection system is simple and flexible enough to
                allow administrators to implement their own policy on how they
                want the load balancing to happen: either on a random,
                load-based, or round robin system. See for details.
            </para>
        </sect1>
        <sect1>
            <title>RC script capabilities</title>
            <para>
                LDM has a very good system for handling user-supplied rc.d
                scripts.  This allows people looking to add site-specific
                customizations to their LTSP setups an easy way to integrate
                this functionality into LTSP.
            </para>
            <para>
                These rc.d scripts can be placed in
                <filename>$CHROOT/usr/share/ldm/rc.d/</filename>.  They are
                executed in the usual rc.d type method, so you must make sure
                that any script you write will not make a call to
                <command>exit</command>.
            </para>
            <para>
                The files start with the letter I, S, K, or X, and have two
                digits after them, allowing you to place them in order of
                execution.  The letters stand for:
            </para>
            <itemizedlist>
                <listitem>
                    <para>
                        <emphasis>I</emphasis> scripts are executed at the
                        start of LDM, before the greeter has been presented.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        <emphasis>S</emphasis> scripts are executed after the user
                        has logged in, but before the X session is run.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        <emphasis>X</emphasis> scripts are executed while the X
                        session is being executed.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        <emphasis>K</emphasis> scripts are executed after the X
                        session has ended, but before the user logs out entirely.
                    </para>
                </listitem>
            </itemizedlist>
            <para>
                Your scripts can make use of the following environment
                variables in the S, X, and K scripts:
            </para>
            <variablelist>
                <varlistentry>
                    <term><varname>LDM_USERNAME</varname></term>
                    <listitem>
                        <para>
                            This is the username the user supplied at login.
                        </para>
                    </listitem>
                </varlistentry>
                <varlistentry>
                    <term><varname>LDM_SOCKET</varname></term>
                    <listitem>
                        <para>
                            The path to the ssh control socket that LDM has open
                            for communication with the server.
                        </para>
                    </listitem>
                </varlistentry>
                <varlistentry>
                    <term><varname>LDM_SERVER</varname></term>
                    <listitem>
                        <para>
                            The current server that LDM is connected to.
                        </para>
                    </listitem>
                </varlistentry>
                <varlistentry>
                    <term><varname>LDMINFO_IPADDR</varname></term>
                    <listitem>
                        <para>
                            The IP address of the thin client.
                        </para>
                    </listitem>
                </varlistentry>
            </variablelist>
            <para>
                You can use these variables to create scripts that customize
                behaviors at login time.  For instance, lets say you were
                running the GNOME desktop environment, and wanted to force your
                users to have blank-only mode for their screen savers, to save
                network bandwidth.
            </para>
            <para>
                Since the script is actually running <emphasis>on the thin
                    client itself</emphasis>, you want this script to set this
                up on the server, where the Gnome session is running.  That's
                where you can make use of the <varname>LDM_SOCKET</varname> and
                <varname>LDM_SERVER</varname> environment variables to run an
                <command>ssh</command> command on the server, using the control
                socket that LDM has set up.  Here's an example script.  You
                could install this into
                <filename>$CHROOT/usr/share/ldm/rc.d/X01-set-blankonly</filename>:
            </para>
            <screen>
#
# sourced with .
#
# Script to automatically switch gnome screensaver to blank
# only mode
#
ssh -S ${LDM_SOCKET} ${LDM_SERVER} "/usr/bin/gconftool-2 --set --type string /apps/gnome-screensaver/mode blank-only"
            </screen>
            <para>
                Using this mechanism, it's easy to customize your LTSP setup to
                your needs.
            </para>
        </sect1>
        <sect1>
            <title>LDM lts.conf parameters</title>
        <xi:include
         href='lts.conf.xml'
         xpointer='lts-conf-ldm-list'
         xmlns:xi='http://www.w3.org/2001/XInclude' />
        </sect1>
        <sect1>
            <title>Multiple server setup</title>
            <para>
                A multiple server setup is useful for larger thin client
                networks. Instead of using one big server, it makes it
                possible to use smaller servers, and dispatch users on them.
                You can adjust computing resources as the demand grows simply
                by adding a new server. To make sure that every server behaves
                the same from the users point of view, new services and
                configurations that are required will be discussed. In
                addition, some configurations specific to thin clients will be
                presented.
            </para>
        </sect1>
    </chapter>
    <chapter id='infrastructure'>
        <title>Infrastructure setup</title>
        <sect1>
            <title>Network topology</title>
            <para>
                The network topology is the same as a standalone server
                setup, except that there are more than one server on the thin
                client LAN.
            </para>
            <para>
                You will need to select one server to behave as the primary
                server. This server will be used to run additional services,
                hold users files, and network boot thin clients.
            </para>
            <para>
                Secondary servers will be used only to run desktop sessions.
                They are simpler, and will be configured to use the central
                services from the primary server.
            </para>
        </sect1>
        <sect1>
            <title>Common authentication</title>
            <para>
                A user should be able to start a session with the same login
                and password, no matter which server it connects to. For this
                purpose, a central authentication mechanism must be used.
                There are many possibilities offered. Here are the major
                technologies:
            </para>
            <orderedlist>
                <listitem>
                    <para>
                        LDAP authentication: On the master server, setup an
                        OpenLDAP server. Configure each servers to use this
                        LDAP server as the authentication base.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        NIS authentication: On the master server, setup a
                        NIS server. Configure each server to use this NIS
                        server for the authentication.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Winbind authentication: Useful if you already have
                        an Active Directory server.
                    </para>
                </listitem>
            </orderedlist>
            <para>
                For detailed instructions, see their respective manuals.</para>
        </sect1>
        <sect1>
            <title>Shared home directories</title>
            <para>
                Shared home directories are easy to setup using an NFS server
                on eithe the primary LTSP server, or even better, a standalone
                NFS server.  Other more modern, faster (and consequently more
                expensive) options include a SAN, and maybe even moving to a
                fibre-channel raid SAN.  Consult your distribution's
                documentation for details and suggestions for setting up an NFS
                server.
            </para>
        </sect1>
        <sect1>
            <title>Shared printers</title>
            <para>
                For printers to be accessible on each server, the cups
                server must be configured to share printers. Refer to the CUPS
                manual for your distribution for detailed setup instructions.
            </para>
            <para>
                Note that an LTSP thin client acting as a print server
                resembles a JetDirect print server.
            </para>
        </sect1>
        <sect1>
            <title>Managing the SSH known hosts file</title>
            <para>
                For security reasons, a thin client won't connect to an
                untrusted server. You must add the keys of secondary servers
                inside the client root on the primary server. To do this,
                first export the key file of the secondary server using LTSP's
                tools. As root, run:
            </para>
            <screen>
ltsp-update-sshkeys --export ssh_known_hosts.myhostname
            </screen>
            <para>
                Then, copy the file
                <filename>ssh_known_hosts.myhostnam</filename>
                to the primary server, in the directory
                <filename>/etc/ltsp/</filename>
                and run <command>ltsp-update-sshkeys</command> on the primary
                server. Then, thin clients will trust the freshly added
                server, and will be able to connect to it.
            </para>
            <para>
                If a secondary server changes it's IP address, then this
                procedure must be repeated.
            </para>
        </sect1>
        <sect1>
            <!-- FIXME: this should be generalized a bit, but since
                 iptables SHOULD be available on ALL distros, it can probably
                 stay.
            -->
            <title>Setting Network Forwarding or Masquerading</title>
            <para>
                The purpose of IP Masquerading is to allow machines with
                private, non-routable IP addresses on your network to access
                the Internet through the machine doing the masquerading.
                Traffic from your private network destined for the Internet
                must be manipulated for replies to be routable back to the
                machine that made the request. To do this, the kernel must
                modify the <emphasis>source</emphasis> IP address of each
                packet so that replies will be routed back to it, rather than
                to the private IP address that made the request, which is
                impossible over the Internet. Linux uses
                <emphasis>Connection Tracking</emphasis>
                (conntrack) to keep track of which connections belong to which
                machines and reroute each return packet accordingly. Traffic
                leaving your private network is thus "masqueraded" as having
                originated from your gateway machine. This process is referred
                to in Microsoft documentation as Internet Connection Sharing.
            </para>
            <para>
                IP Forwarding with IP Tables
            </para>
            <orderedlist>
                <listitem>
                    <para>
                        to enable IPv4 packet forwarding by editing
                        /etc/sysctl.conf and uncomment the following
                        line:</para>
                    <screen>net.ipv4.ip_forward=1</screen>
                </listitem>
                <listitem>
                    <para>
                        If you wish to enable IPv6 forwarding also
                        uncomment:
                    </para>
                    <screen>net.ipv6.conf.default.forwarding=1</screen>
                </listitem>
                <listitem>
                    <para>
                        Next, execute the sysctl command to enable the new
                        settings in the configuration file:
                    </para>
                    <screen>sudo sysctl -p</screen>
                </listitem>
                <listitem>
                    <para>
                        IP Masquerading can now be accomplished with a
                        single iptables rule, which may differ slightly based
                        on your network configuration:
                    </para>
                    <screen>sudo iptables -t nat -A POSTROUTING -s 192.168.0.0/16 -o eth0 -j MASQUERADE</screen>
                    <para>
                        The above command assumes that your private address
                        space is 192.168.0.0/16 and that your Internet-facing
                        device is eth0. The syntax is broken down as follows:
                    </para>
                </listitem>
            </orderedlist>
        </sect1>
    </chapter>
    <chapter id='session-dispatching'>
        <title>Session dispatching</title>
        <sect1>
            <title>Define the server list</title>
            <para>
                LDM is a login manager for thin clients. Users can select a
                server from the available ones in the host selection dialogue
                box.
            </para>
            <para>
                The displayed server list is defined by the
                <varname>LDM_SERVER</varname>
                parameter. This parameter accepts a list of server IP address
                or host names, separated by space. If you use host names, then
                your DNS resolution must work on the thin client. If defined
                in the &lts.conf; file, the list order will
                be static, and the first server in the list will be selected
                by default.
            </para>
            <para>
                You can also compute a new order for the server list, by
                creating the script
                <command>/opt/ltsp/&lt;arch&gt;/usr/share/ltsp/get_hosts</command>
                . The parameter
                <varname>LDM_SERVER</varname>
                overrides the
                script. In consequence, this parameter must not be defined if
                the <command>get_hosts</command> is going to be used. The
                <command>get_hosts</command>
                script writes on the standard output each server IP address or
                host names, in the chosen order.
            </para>
        </sect1>
        <sect1>
            <title>Dispatching method</title>
            <para>
                You can change this behaviour by using a script to rearrange
                the list. The simplest way to do it is by randomizing the
                list. First, define a custom variable in the file
                &lts.conf;
                , for example <varname>MY_SERVER_LIST</varname>, that will
                contain the list of servers, the same way as
                <varname>LDM_SERVER</varname>
                Then, put the following script in
                <command>/opt/ltsp/&lt;arch&gt;/usr/share/ltsp/get_hosts</command>
            </para>
            <screen>
#!/bin/bash
# Randomize the server list contained in MY_SERVER_LIST parameter
TMP_LIST=""
SHUFFLED_LIST=""

for i in $MY_SERVER_LIST; do
    rank=$RANDOM
    let "rank %= 100"
    TMP_LIST="$TMP_LIST\n${rank}_$i"
done

TMP_LIST=$(echo -e $TMP_LIST | sort)
for i in $TMP_LIST; do
    SHUFFLED_LIST="$SHUFFLED_LIST $(echo $i | cut -d_ -f2)"
done
echo $SHUFFLED_LIST
            </screen>
            <para>
                More advanced load balancing algorithms can be written. For
                example, load balancing can be done by querying ldminfod for
                the server rating. By querying ldminfod, you can get the
                current rating state of the server. This rating goes from 0 to
                100, higher is better. Here is an example of such a query:
                <screen>nc localhost 9571 | grep rating | cut -d: -f2</screen>
            </para>
        </sect1>
        <sect1>
            <title>Network Swap</title>
            <para>
                Just like on a full fledged workstation, it helps to have
                swap defined for your thin client. "Swap" is an area of disk
                space set aside to allow you to transfer information out of
                ram, and temporarily store it on a hard drive until it's
                needed again. It makes the workstation look like it has more
                memory than it actually does. For instance, if your
                workstation has 64 Megabytes of ram and you configure 64
                Megabytes of swap, it's theoretically possible to load a 128
                Megabyte program.
            </para>
            <para>
                We say, "theoretically", because in practice, you want to
                avoid swapping as much as possible. A hard drive is several
                orders of magnitude slower than ram, and, of course, on a thin
                client, you don't even have a hard drive! You have to first
                push the data through the network to the server's hard drive,
                thus making your swapping even slower. In practice, it's best
                to make sure you have enough ram in your thin client to handle
                all your average memory needs.
            </para>
            <para>
                However, sometimes that's not possible. Sometimes, you're
                re-using old hardware, or you've simply got a program that
                isn't normally used, but does consume a lot of ram on the thin
                client when it does. Fortunately, LTSP supports swapping over
                the network via NBD, or Network Block Devices. We include a
                small shell script called nbdswapd, which is started via
                inetd. It handles creating the swap file, and setting up the
                swapping, and removing the swap file when it's no longer
                needed, after the terminal shuts down.
            </para>
            <para>
                By default, swap files are 64 Megabytes in size. This was
                chosen to give your workstation a little extra ram, but not
                use up too much disk space. If you get some random odd
                behaviour, such as Firefox crashing when viewing web pages
                with a lot of large pictures, you may want to try increasing
                the size of the swap files. You can do so by creating a file
                in the directory <filename>/etc/ltsp</filename> on the LTSP
                server, called <filename>nbdswapd.conf</filename>. In it, you
                can set the SIZE variable to the number of Megabytes you wish
                the file to be sized to. For instance, to create 128 Megabyte
                files, you'll want: SIZE=128 in the <filename>nbdswapd.conf</filename> file.
            </para>
            <para>
                Please note that this is a global setting for all swap files.
                If your server has 40 thin clients, each using 128 Megs of
                memory, you'll need 128 * 40 = 5120, or a little over 5
                Gigabytes of space in your <filename>/tmp</filename>
                directory, where the swap files are stored.
            </para>
        </sect1>
        <sect1>
            <!-- FIXME: Beginning to get too distro specific, and if people
            want us to move to DNSMASQ, then this all changes anyway.  Try to
            generalize a bit more.
            -->
            <title>Managing DHCP</title>
            <para>
                DHCP stands for Dynamic Host Configuration Protocol and is the
                very first thing your thin client uses to obtain an IP address
                from the network, in order to allow it to start booting. In
                LTSP, the dhcpd file is located in <filename>/etc/ltsp</filename>.
                Any changes you want to make to booting behaviour should be made there.
            </para>
            <para>
                By default, LTSP ships a <filename>dhcpd.conf</filename> that
                serves thin clients in a dynamic range (i.e. it will hand out
                ip addresses to anyone who asks for them) from 192.168.0.20 to
                192.168.0.250. The default dhcpd.conf file looks like:
            </para>
            <screen>
#
# Default LTSP dhcpd.conf config file.
#

authoritative;

subnet 192.168.0.0 netmask 255.255.255.0 {
    range 192.168.0.20 192.168.0.250;
    option domain-name "example.com";
    option domain-name-servers 192.168.0.1;
    option broadcast-address 192.168.0.255;
    option routers 192.168.0.1;
#    next-server 192.168.0.1;
#    get-lease-hostnames true;
    option subnet-mask 255.255.255.0;
    option root-path "/opt/ltsp/i386";
    if substring( option vendor-class-identifier, 0, 9 ) = "PXEClient" {
        filename "/ltsp/i386/pxelinux.0";
    } else {
        filename "/ltsp/i386/nbi.img";
    }
}
            </screen>
            <para>
                This <filename>dhcpd.conf</filename> should handle most
                situations.
            </para>
            <para>
                By default, LTSP will detect an unused network interface and
                configure it to be 192.168.0.254. LTSP's recommended single
                server installation is to use a separate network interface for
                the thin clients. If, however, you're not using two network
                interfaces, or you already have an interface in the 192.168.0
                range, then you might have to configure the thin client
                interface differently, which means you may have to adjust the
                <filename>dhcpd.conf</filename> accordingly.
            </para>
            <para>
                If the network interface that you're going to connect the thin
                clients to has, say, a TCP/IP address of 10.0.20.254, you'll
                want to replace every occurrence of 192.168.0 with 10.0.20 in
                the <filename>dhcpd.conf</filename> file.
            </para>
            <para>
                Always remember, you'll need to re-start the dhcp server if
                you make any changes. You can do this by issuing the command:
            </para>
            <screen>sudo invoke-rc.d dhcp3-server restart</screen>
            <para>(at the command prompt.)</para>
        </sect1>
    </chapter>
    <chapter id='static-entries-dhcp'>
        <title>Adding static entries to the dhcpd.conf</title>
        <para>
            Sometimes, you may need to have a certain terminal boot with a
            guaranteed fixed TCP/IP address every time. Say, if you're
            connecting a printer to the terminal, and need to make sure the
            print server can find it at a fixed address. To create a fixed
            address, use a low number in the range of 2-19, or otherwise, if
            you change the range statement in the <filename>dhcpd.conf</filename>.
        </para>
        <para>
            To create a static entry, simply add the following after the
            "option root-path" line:
        </para>
        <screen>
host hostname {
    hardware ethernet MA:CA:DD:RE:SS:00;
    fixed-address 192.168.0.2;
}
            </screen>
            <para>
                Substitude the MAC
            address for the mac address of the thin client you wish to fix the
            address of. The fixed-address will be the TCP/IP address you want,
            and "hostname" is the name you wish to give the host. This kind of
            setup is relatively complex and the admin should have a full
            understanding of how DHCP works before attempting such a setup.
            For more information, check the Internet.
        </para>
    </chapter>
    <chapter id='dhcp-loadbalance'>
        <title>DHCP failover load balancing</title>
        <para>
            Another common method of load balancing is to use DHCP
            load balancing. There's an excellent writeup on the topic at:
            <ulink url="https://wiki.edubuntu.org/EdubuntuDHCPload-balancingFailover">
                https://wiki.edubuntu.org/EdubuntuDHCPload-balancingFailover
            </ulink>
        </para>
        <sect1>
            <!-- FIXME: Should mention KDE's lockdown, and not go into so much
            detail.  Generalize a bit.
            -->
            <title/>
            <sect2>
                <title>Lockdown with Sabayon (user profile manager) and
                    Pessulus (lockdown editor)
                </title>
                <para>
                    A common requirement in both schools and businesses is
                    having the ability to lock down the desktop and provide
                    certain default configurations.
                </para>
                <para>
                    In LTSP, the applications you'll want to use are Sabayon
                    and Pessulus. You'll want to add them from the package
                    manager.
                </para>
                <para>
                    The Sabayon user profile editor looks like a window that
                    contains a smaller sized picture of your desktop. Within
                    this window, you can create a default layout: add icons to
                    panels and the desktop, lock down the panels so they can't
                    be modified, remove access to the command line, etc.
                </para>
                <para>
                    Once you're done, you can save your profile. You have
                    the option of applying your profile to either individual
                    users, or all users on the system. Please consult the
                    manual included with Sabayon for all the details.
                </para>
                <para>
                    More information is available here:</para>
                <para>
                    <ulink url="http://live.gnome.org/PythonSabayon">
                        http://live.gnome.org/PythonSabayon
                    </ulink>
                </para>
                <para>
                    <ulink url="http://www.gnome.org/~seth/blog/sabayon">
                        http://www.gnome.org/~seth/blog/sabayon
                    </ulink>
                </para>
                <para>
                    http://www.gnome.org/projects/sabayon/</para>
            </sect2>
        </sect1>
        <sect1>
            <title>Replication of desktop profiles</title>
            <para>
                If you customize user's desktop, then custom desktop profiles
                should be copied to every server. Gnome desktop profiles
                created with Sabayon are located in
                <filename>/etc/desktop-profiles</filename>
            </para>
        </sect1>
    </chapter>
    <chapter id='managing-clients'>
        <!-- FIXME: Same.  Too Gnome specific, and not really part of LTSP.
        Should just provide a pointer to a wiki page.
        -->
        <title>Managing the thin client</title>
        <para>
            Previously, there was a program called TCM or thin client
            manager, which was responsible for checking what was happening on
            the various thin terminals, messaging between them, locking, or
            generally offering support from a master terminal. This has now
            been replaced by the use of Italc, which must be separately
            installed depending on your distribution.
        </para>
        <sect1>
            <title>Lockdown Editor</title>
            <para>
                By choosing a single user and right clicking on that users
                name, you will open up the context menu. From here you can
                choose "Lockdown", which will allow you to set options to
                restrict a particular user. Clicking this menu item will
                invoke the "Pessulus" program, which is the Gnome lockdown
                editor. Ticking and unticking options in Pessulus will enable
                and disable certain functions for that particular user. There
                is a padlock next to each option in Pessulus. Ticking this
                will make the option unchangeable by the user. This is called
                a mandatory setting. For further help with Pessulus, please
                refer to the Pessulus documentation.
            </para>
        </sect1>
    </chapter>
    <chapter id='updating-chroot'>
        <!-- FIXME: Distro specific.  Mention using a package manager to
        update, and point them to a wiki page with more specific information.
        -->
        <title>Updating your LTSP chroot</title>
        <para>
            At some point in the future, updates will become available for
            your LTSP server. You must remember that although you may have
            applied all the updates to the server itself, as in the
            instructions....HERE it is likely that the LTSP chroot will also
            need updating. To do this you must open up a terminal and use the
            following commands.
        </para>
        <para>
            First make sure the Client environment has the same Package
            lists as the Server, to achieve that, you will copy the
            /etc/apt/sources.list (on Debian and Ubuntu) or the
            /etc/yum.repos.d/fedora.repo  file from the Server to the Client
            environment.
        </para>
        <para>
            Now issue the command below.</para>
        <screen>sudo chroot /opt/ltsp/&lt;arch&gt;</screen>
        <para>(replace &lt;arch&gt; with the architecture
            you are working with.)
        </para>
        <para>
            This will change your root directory to be the LTSP clients root
            directory. In essence, anything you now do inside here, will be
            applied to the LTSP clients root. This is a separate small set of
            files that are used to boot the clients into a usable, and enable
            them to contact the LTSP server. Once inside this shell, we must
            type the following command to obtain the latest list of packages
            from the apt/yum servers.
        </para>
        <screen>apt-get get update</screen>
        <para>
            on Debian and Ubuntu
        </para>
        <para>
            You need to mount <filename>/proc</filename> in the chroot before beginning, as some of
            the packages you install may need resources in <filename>/proc</filename> to install correctly.
        </para>
        <screen>mount -t proc proc /proc</screen>
        <para>
            To be sure no deamons are started do the following:</para>
        <screen>export LTSP_HANDLE_DAEMONS=false</screen>
        <para>
            Once this has completed you will have to upgrade the software in
            the chroot by running the following command:
        </para>
        <screen>apt-get upgrade</screen>
        <para>(on Debian and Ubuntu)</para>
        <para>
            or
        </para>
        <screen>yum update</screen>
        <para>(on Fedora)</para>
        <para>
            Just in case <filename>/proc</filename> is still mounted when you exit the chroot,
            unmount it first by doing:</para>
        <screen>umount /proc</screen>

        <para>
            Once you're done, you must leave the chroot by either typing
            <emphasis>exit</emphasis>
            or by using the key combination Ctrl+D. This will return you to
            the root of the server.
        </para>
        <para>
            If your kernel has been upgraded you must run the LTSP kernel
            upgrade script, to ensure that your LTSP chroot uses the latest
            version. This is performed by running the command below:
        </para>
        <screen>ltsp-update-kernels</screen>
        <para>
            All of your clients will now use the latest kernel upon their
            next reboot.
        </para>
        <para>
            Finally, you must remember to rebuild the NBD boot image from
            your chroot with the following command:
        </para>
        <screen>ltsp-update-image</screen>
        <para>(add architecture using -arch= addition)</para>
        <para>
            Be advised that this may take a few minutes, depending on the
            speed of your server.
        </para>
    </chapter>
    <chapter id='changing-server-ip'>
        <title>Changing the IP of your LTSP server</title>
        <para>
            At some point in time, it may become necessary to change the IP
            address of your LTSP server. Normally this does not present an
            issue, but LTSP servers and clients communicate over and encrypted
            channel and require all SSL certificates to be updated. Without
            this update, <emphasis>no LTSP clients will be able to log in</emphasis>.
            This is done by simply opening a terminal and running the following command.
        </para>
        <screen>
sudo ltsp-update-sshkeys
sudo ltsp-update-image
        </screen>
    </chapter>
    <chapter id='appendix'>
        <title>Appendix I</title>
        <para>
            Here you can find some solutions to common questions and
            problems.
        </para>
        <sect1>
            <title>Using NFS instead of NBD</title>
            <para>
                Using NBD instead of NFS has several advantages:</para>
            <orderedlist>
                <listitem>
                    <para>
                        Using a squashfs image we can now merge that
                        together in a unionfs to get writeable access which is
                        a lot faster during bootup.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        A squashed root filesystem uses less network
                        bandwidth.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Many users and administrators have asked us to
                        eliminate NFS, for reasons of site policy. Since the
                        squashed image is now served out by nbd-server, which
                        is an entirely userspace program, and is started as
                        the user nobody, this should help to eliminate
                        concerns over NFS shares.
                    </para>
                </listitem>
            </orderedlist>
            <para>
                However, some people still want to use NFS. Fortunately,
                it's easy to switch back to NFS, if it's so desired:
            </para>
            <orderedlist>
                <listitem>
                    <para>
                        On the server, use the chroot command to maintain
                        the LTSP chroot:</para>
                    <screen>sudo chroot /opt/ltsp/&lt;arch&gt;</screen>
                </listitem>
                <listitem>
                    <para>
                        Now edit /etc/default/ltsp-client-setup and change
                        the value of the root_write_method variable to use
                        bind mounts instead of unionfs, it should look like
                        this afterwards:
                    </para>
                    <screen>root_write_method="bind_mounts"</screen>
                </listitem>
                <listitem>
                    <para>
                        Next, create the file
                        <filename>/etc/initramfs-tools/conf.d/ltsp</filename> and add the following
                        line (set the value of the BOOT variable to nfs):
                    </para>
                    <screen>BOOT=nfs</screen>
                </listitem>
                <listitem>
                    <para>
                        Regenerate the initramfs: </para>
                    <screen>update-initramfs -u</screen>
                </listitem>
                <listitem>
                    <para>
                        Hit CTRL-D to exit the chroot now. Make sure LTSP
                        uses the new initramfs to boot:
                    </para>
                    <screen>sudo ltsp-update-kernels</screen>
                </listitem>
            </orderedlist>
        </sect1>
        <sect1>
            <title>Enabling dual monitors</title>
            <para>
                First, I am going to start with a couple assumptions:</para>
            <itemizedlist>
                <listitem>
                    <para>
                        I will assume that you are operating thin clients
                          with an NBD file system in this write-up.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        I will assume that you are running Ubuntu 8.04.1</para>
                </listitem>
                <listitem>
                    <para>
                        I will assume that you are running LTSP 5</para>
                </listitem>
                <listitem>
                    <para>
                        I will assume that you are replacing a running
                        image that has been properly tested, and is working.
                    </para>
                </listitem>
            </itemizedlist>
            <para>
                Create a
                new image to ensure your configuration is congruent with my
                successfully tested configuration.
            </para>
            <screen>
sudo ltsp-build-client --copy-sourceslist --arch i386
            </screen>
            <para>
                (note the --arch i386 command is required for my system
                because it's running an amd64 kernel. It may not be required
                for individuals running a 32-bit kernel)
            </para>
            <para>
                Download the pertinent VIA unichrome driver for your chipset
                from this web site: <ulink url="http://linux.via.com.tw/support/downloadFiles.action">
                    http://linux.via.com.tw/support/downloadFiles.action
                </ulink>
                Be sure to select the proper OS as well. The installation
                script is set up specifically for the directory structure of
                each OS, and will error out if the wrong OS release is
                installed. Next we need to move the downloaded file to the
                image directory
            </para>
            <screen>
cp /home/&lt;username/Desktop/chrome9.83-242-sl10.1.tar.gz /opt/ltsp/i386
            </screen>
            <para>
                After that, we need to chroot to the same image directory.</para>
            <screen>
sudo chroot /opt/ltsp/i386/
            </screen>
            <para>
                Unpack the driver in the root directory </para>
            <screen>
tar -zxvf chrome9.83-242-sl10.1.tar.gz
            </screen>
            <para>
                After unpacking, enter the directory:</para>
            <screen>
cd chrome9.83-242-sl10.1/
            </screen>
            <para>
                Run the file contained inside to start the driver installation
            </para>
            <screen>
./vinstall ..................done! Original X config file
was saved as /etc/X11/xorg.conf.viabak
            </screen>
            <para>(The following error: "VIAERROR:The /etc/X11/xorg.conf is
                missing!" Can be ignored. We will be replacing the xorg.conf
                anyway, and the drivers are still installed properly.)
            </para>
            <para>
                Next we need to put a proper xorg.conf in to the proper
                directory.
            </para>
            <screen>
gedit /etc/X11/xorg.conf
            </screen>
            <para>
                Now paste the following in to the empty file:
            </para>
            <screen>
Section "Module"
    Load "extmod"
    Load "dbe"
    Load "dri"
    Load "glx"
    Load "freetype"
    Load "type1"
EndSection

Section "Files"
    RgbPath "/usr/X11R6/lib/X11/rgb"
    FontPath "/usr/X11R6/lib/X11/fonts/misc/"
    FontPath "/usr/X11R6/lib/X11/fonts/75dpi/:unscaled"
    FontPath "/usr/X11R6/lib/X11/fonts/75dpi/"
    FontPath "/usr/X11R6/lib/X11/fonts/Type1"
    FontPath "/usr/X11R6/lib/X11/fonts/TTF"
EndSection

Section "ServerFlags"
    Option "Dont Zoom"
    Option "AllowMouseOpenFail" "Yes"
    Option "BlankTime" "20"
    Option "StandbyTime" "0"
    Option "SuspendTime" "0"
    Option "OffTime" "0"
    Option "Xinerama" "on"
EndSection

Section "InputDevice"
    Identifier "Keyboard1"
    Driver "Keyboard"
    Driver "keyboard"
    Option "AutoRepeat" "500 30"
    Option "XkbRules" "xfree86"
    Option "XkbModel" "pc105"
    Option "XkbLayout" "en_US,en_US"
    Option "XkbOptions" "grp:alt_shift_toggle,grp_led:scroll" EndSection
EndSection

Section "InputDevice"
    Identifier "USBMouse"
    Driver "mouse"
    Option "Protocol" "IMPS/2"
    Option "Device" "/dev/input/mice"
    Option "ZAxisMapping" "4 5"
    Option "Buttons" "5"
EndSection

Section "InputDevice"
    Identifier "Mouse1"
    Driver "mouse"
    Option "Protocol" "Auto"
    Option "Device" "/dev/psaux"
    Option "ZAxisMapping" "4 5"
    Option "Buttons" "5"
EndSection

Section "Monitor"
    Identifier "Monitor0"
    HorizSync 31.5-48.5
    VertRefresh 60
    Option "DPMS"
EndSection

Section "Device"
    Identifier "CN700"
    Driver "via"
    VideoRam 16384
    Screen 0
    Option "NoDDCValue" "1"
    Option "Simultaneous"
    Option "DPMS" "on"
    BusID "PCI:1:0:0"
EndSection

Section "Screen"
    Identifier "Screen0DVI"
    Device "CN700DVI"
    Monitor "Monitor0DVI"
    DefaultDepth 24
    Subsection "Display"
        Depth 8
        Modes "1280x1024"
        ViewPort 0 0
    EndSubsection
    Subsection "Display"
        Depth 16
        Modes "1280x1024"
        ViewPort 0 0
    EndSubsection
    Subsection "Display"
        Depth 24
        Modes "1280x1024"
        ViewPort 0 0
    EndSubsection
EndSection

Section "Monitor"
    Identifier "Monitor0"
    HorizSync 31.5-48.5
    VertRefresh 60
    Option "DPMS"
EndSection

Section "Device"
    Identifier "CN700DVI"
    Driver "via"
    VideoRam 16384
    Screen 1
    Option "NoDDCValue" "1"
    Option "Simultaneous"
    Option "DPMS" "on"
    BusID "PCI:1:0:0"
EndSection

Section "Screen"
    Identifier "Screen0"
    Device "CN700"
    Monitor "Monitor0"
    DefaultDepth 24
    Subsection "Display"
        Depth 8
        Modes "1280x1024"
        ViewPort 0 0
    EndSubsection
    Subsection "Display"
        Depth 16
        Modes "1280x1024"
        ViewPort 0 0
    EndSubsection
    Subsection "Display"
        Depth 24
        Modes "1280x1024"
        ViewPort 0 0
    EndSubsection
EndSection

Section "ServerLayout"
    Identifier "Simple Layout"
    Screen "Screen0" 0 0
    Screen 1 "Screen0DVI" LeftOf "Screen0"
    InputDevice "Mouse1" "CorePointer"
    InputDevice "Keyboard1" "CoreKeyboard"
    InputDevice "USBMouse" "AlwaysCore"
EndSection
            </screen>
            <para>
                <emphasis>IMPORTANT NOTE</emphasis> IN THE ABOVE SECTION PASTED INTO THE XORG.CONF, NOTICE
                THAT THERE ARE RESOLUTIONS SPECIFIED PER MONITOR. PLEASE
                ENSURE THAT YOU HAVE THE PROPER RESOLUTIONS FOR YOU YOUR
                MONITOR ENTERED ON THOSE AREAS. Be sure to save the file as
                xorg.conf and exit out of your chroot'd image. &lt;CTRL+D or
                "exit"&gt; next we need to put in an addendum in the
                lts.conf
            </para>
            <screen>
gedit /var/lib/tfpboot/ltsp/i386/lts.conf
            </screen>
            <para>
                Feel
                free to comment out anything that you need to in the lts.conf.
                I will include my full lts.conf as an example:
            </para>
            <screen>
[DEFAULT]
    #X_COLOR_DEPTH = "16"
    #X_MODE_0 = "1680x1050"
    #X_VERTREFRESH = "43-61"
    #X_HORZSYNC = "28-85"
    #X_OPTION_01 = "\"ForcePanel\" \"True\""
    #X_OPTION_01 = "\"NoPanel\" \"true\""
    #SCREEN_02 = shell
    #SCREEN_07 = ldm
    X_CONF = /etc/X11/xorg.conf
            </screen>
            <para>
                Feel free to copy-paste this in it's
                entirety if you want, but you will only need the last line.
                After you add the X_CONF line, save &amp; exit. Now we need to
                make the changes that we have made take effect in the image
            </para>
            <screen>
# sudo ltsp-update-image --arch i386
            </screen>
            <para>(again, the --arch i386
                will not be required for most, but I am putting it in just in
                case a user has a x64 installation on their server.) That
                should do it! Boot up the client and you should be good to go.
            </para>
        </sect1>
    </chapter>
</book>