Thin Client: New User Guide

Table of Contents

  1. Introduction

  2. Hardware and Documentation

     2.1 Hardware
     2.2 Documentation

  3. Server setup

     3.1 Check your network services on your server
     3.2 Setting up a dhcpd daemon
     3.3 Tftpd setup
     3.4 Kernel image
     3.5 Security

  4. Client setup

  5. Network files system

     5.1 server specific
     5.2 client specific

  6. X-terminal

  7. Acknowledgments & further exercises


  1.  Introduction

  o  Linux allows any reasonably new computer to be used as a server to
     a thin client, or many thin clients, these thin clients can be
     inexpensive legacy computers. For a console terminal you need a 386
     with 4-8mb of ram, or for an X-Terminal a 486/66 with 8-16mb ram.

  o  One Option is without a hard drive, it keeps the noise down and
     simplifies administration as you only have one system to maintain.

  o  If you have legacy apps, you can have them on a hard drive with
     it's legacy Operating System

  o  This howto is aimed at those new to Unix/Linux, it will cover the
     essential areas you need to be aware of and point you to other
     documentation in that area you need to be familiar with.

  o  You will probably use this as an aid to the  documentation, I include some
     more examples of config files, and leave many of the other features
     of etherboot as an exercise for the reader

  o  If your client is sufficiently powerful only the file system need
     be shared, applications can run on the client system. (say a 233
     32mb ram).  Install an application on the server and all clients
     have access

  2.  Hardware and Documentation

  2.1.  Hardware

  When you start, you will need at least this

  o  a computer to act as Server,

  o  a client computer, I unplugged the power to the hard disk and
     disabled the drive in the bios to emulate a diskless machine

  o  compatible network cards

  o  connection between computers, I used twisted pair ethernet with
     RJ45 terminators

  o  For two computers a cross-over cable  is sufficient, and saves
     another power point, the first computer shop I went to gave me
     blank stares, idiots !

  o  For two or more clients, you need a hub, a kit with a 10 mb 4 port
     hub ,2 cards sells for under A$150, you can probably do better,
     I've had some success with $5 second hand cards, 3m cables for $6,
     a new hub for $40, a found monitor and a $60 pentium 75

  2.2.  Documentation

  You may like to familiarise yourself with the linux documentation,
  specifically you can read (skim) for an overview the following :

  o  /usr/doc/HOWTO/mini/Diskless - a similar howto tackling this

  o  Networking Overview HOWTO - Networking capabilities of the Linux

  o  Ethernet HOWTO -  Information on Ethernet hardware compatibility

  o  NET-3 HOWTO -  How to configure TCP/IP networking under Linux.

  Also you probably have in the  /usr/doc/LDP/ directory

  o  The System Administrators' Guide

  o  The Network Administrators' Guide

  o  Linux Installation and Getting Started

  The obligitory link

  o help for new linux users.

  One last thing

  o  my network server is snoball , my client is elite and my
     (local)domain is Replace with your computers names where

  3.  Server setup

  The server needs to be setup in readiness for the client in a number
  of ways

  3.1.  Check your network services on your server

  run the command /sbin/ifconfig if your output is similar to below then
  your loopback and ethernet card are correctly configured.

  [cassie@snoball cassie]$ /sbin/ifconfig
  lo        Link encap:Local Loopback
       inet addr:  Bcast:  Mask:
       RX packets:854 errors:0 dropped:0 overruns:0 frame:0
       TX packets:854 errors:0 dropped:0 overruns:0 carrier:0
  eth0      Link encap:Ethernet  HWaddr 00:AA:00:BB:BD:09
       inet addr:  Bcast:  Mask:
       RX packets:190369 errors:0 dropped:0 overruns:0 frame:0
       TX packets:249267 errors:0 dropped:0 overruns:0 carrier:1
       collisions:4793           Interrupt:5 Base address:0x320

  If not ...

  o  loopback, if this isn't here you need to activate it at start up,

  o  ethernet card, is it being detected,is the driver a module

  o  you can set these in linuxconf or netcfg

  3.2.  Setting up a dhcpd daemon

  Here the server gives out IP numbers to requests by clients

  o  is DHCPD installed, maybe (as root) just run ntsysv and have it
     start at boot time

  o  this /etc/dhcpd.conf file assigns static IP numbers if you have a
     matching MAC address, A MAC address is a unique 'number' given to
     the NIC.  The start of the 'number' is based on the manufacturer,
     if you don't have a sticker on the card, attempt to load the rom
     image from eprom or floppy and see what it reports. (see client

     subnet netmask {
         option domain-name "";
         range dynamic-bootp;
         default-lease-time 21600;
         max-lease-time 43200;

     host 286 {
             filename "/tftpboot/kermit.nb";
             hardware ethernet 00:80:c8:22:ae:de;

     host elite {
         filename "/tftpboot/vmlinuz.xterm";
         hardware ethernet 00:00:79:80:34:c9;
             option host-name "elite";

  o  the /etc/hosts file resolves IP numbers into host names

     #etc/hosts       localhost    localhost.localdomain    snoball   elite

  3.3.  Tftpd setup

  trivial ftp - after you have your IP number your client requests a
  kernal, this is delivered over ethernet.

  o  Install tftpd, make sure it's active in /etc/inetd.conf, typical

     tftp dgram udp wait root /usr/sbin/tcpd in.tftpd -s /tftpboot

  restart inetd, kill -HUP "process id of inetd"

  3.4.  Kernel image

  You must compile a kernel for the Client that includes NFS support and
  the NIC driver for that client compiled in (not modules).  Answer yes
  to Root file system on NFS? and BOOTP support?

  After building the kernel, run mknbi-linux from the Etherboot
  distribution on it.(the mknbi program in the netboot/linux directory)
  Install this tagged image as /tftpdir/"vmlinuz.xterm".

  see etherboot-4.2/doc/html/README-3.html

  should i put a copy of mine somewhere for download RH6.0 ne2000 NIC

  3.5.  Security

  It's easiest to allow anybody and anything to run services and process
  on your computer, but one day you will be sorry. You restrict these by
  your /etc/hosts.deny and specifically restore rights by
  /etc/hosts.allow, indicative examples :

  # all except those in hosts.allow

  #only hosts within my domain and my host at home.
  ALL:LOCAL, 192.168.53.       #<-- note:no space after :

  more security - look for more information in the ldp-howto's and if
  your using etherboot, in it's security howto.

  4.  Client setup

  Network loader

  A small program that runs as a BIOS extension, can be loaded from a
  floppy, or you can burn an eprom chip and insert it on your network
  card for a totally diskless client. It handles the DHCPD query and
  TFTP loading and then transfers control to the loaded image. It uses
  TCP/IP protocols.

  There are two free implementations of TCP/IP net loaders: Etherboot
  and Netboot: Etherboot uses built-in drivers while Netboot uses Packet

  o  see etherboot-4.2/doc/html/README-2.html,

  o  I compiled the option to ask local or Network and default to local
     after 5 seconds

  o  making a boot rom floppy, floppyload.bin was tricky to find, I
     copied it into the directory of compiled rom images

     cat floppyload.bin ne2000.lzrom > /dev/fd0

  5.  Network files system

  The Client requests to mount /tftpboot/<IP address of client> as its /
  by NFS from server. You must export this from the server,(maybe
  symlink to /tftpboot/client to be safe.)

  NFS is a big topic there is a HOWTO and two mini Howto's.

  first you need to create a copy of your current system under /tftpboot
  ken has written two scripts that do all your work, I called them
  makefirst and makecopy. my first client takes 20-30mb and the copy
  less. I used du -h to look for large unnecesary files.

  see etherboot-4.2/doc/html/diskless-5.html

  the following seem to me to be the critical files here

  5.1.  server specific

  /tftpboot/elite             elite(rw,no_root_squash)
  /tftpboot/elite             gordon(rw,no_root_squash)
  /usr                        *
  /home                       *
  /mnt/cdrom                  (ro)

  run exportfs -a  to reread the exports file after
  changes /usr/sbin/exportfs --help

  HOSTNAME="snoball"         <-----------

  IPADDR=""            <-----------

  5.2.  client specific

  snoball:/tftpboot/elite    /               nfs rw  1 1
  none                    /proc proc          defaults   0 0
  snoball:/usr           /usr                 nfs     ro  1 1
  snoball:/home          /home                nfs     rw  1 1

  GATEWAY=""       <-----------

  IPADDR=         <-----------

  #odd fiddles #itemize> #item>fast...  #item>cp /usr/bin/xargs
  /tftpboot/client/bin/xargs #/itemize>

  6.  X-terminal

  With no further changes your client should boot on the CLIENT pc, it
  just happens to be sharing it's files via NFS

  At this point you have a console terminal. you need to make just a few
  more changes to run X

  o  Configuring X

     As root on client run Xconfigurator and mouseconfig,

     If this fails use XF86Setup check your RPMS dir on your CD (

  o  X Font Server

     #chech how xfs starts on server /etc/rc.d/init.d/xfs
         echo -n "Starting X Font Server: "
         rm -fr /tmp/.font-unix
         daemon --check xfs su xfs -c xfs -s /bin/sh
         touch /var/lock/subsys/xfs

     #edit XF86Config for all machines
         FontPath  "tcp/snoball:7100"

  o  Console login

     You are now set up for a console login to the client PC. You are
     using the client memory and processor, this is adequate for console
     programs and there and many or great merit, program in python,
     email with pine or browse with lynx.

     You may still start X from here, make the server changes in the
     next section, at the prompt type X -query snoball and you will get
     the login box to the server

  o  Graphical login

     Server set up

     1. Make sure the client is matched by a clause in /etc/X11/xdm/Xaccess
     *   CHOOSER BROADCAST   #any indirect host can get a chooser

     2. Comment out the :0 in /etc/X11/xdm/Xservers
     #:0 local /usr/X11R6/bin/X

     3. Then make sure that xdm is run from the init scripts.

     # Run xdm in runlevel 5
     # xdm is now a separate service
     x:5:respawn:/etc/X11/prefdm -nodaemon
     xdm:5:respawn:/usr/X11R6/bin/xdm -nodaemon

  On the client

  Get the slow PC's to run on the server, Fast PC's (eg 166mhz 32mb
  ram)can run ok on their own CPU and memory

  the part maarked WARNING dosn't actually work as yet, but I'm close to
  getting the syntax correct, use the two stage method via the console
  login in the mean time.


  id:5:initdefault:                                    #WARNING
  x:5:respawn:/usr/X11R6/bin/Xwrapper -query snoball   #WARNING

  OR to run on client ??

  id:3:initdefault:                                    #runlevel 3 ie console
  x:5:respawn:/etc/X11/prefdm -nodaemon

  7.  Acknowledgments & further exercises

  Markus Gutschke and Ken Yap the authors of the Etherboot program.

  Extend your system with the following programs

  o  squid -      cache your web browsing for others on your network

  o  junkbuster - banish web banner adds

  o  mailman -    mailinglist ;setup via e-mail or web

  o  imp -        web based email (with a java enabled browser)

  o  python -     for some Java and C is just too hard

  o  sgmltools -  knock out multiple versions of your docs

  o  suggestions ?

  stephen7 at

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