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Thin Client: New User Guide
Stephen Noble stephen7 at bigfoot.com
30th November 1999
1.How to turn inexpensive legacy computers into fast terminals using
the power of your main computer, you will need : A fast computer to
act as Server, A client computer (old and unwanted). Linux compatible
network cards. A connection between computers. 2.How to centralise
system administaration by useing NFS, ie placing the entire file sys-
tem of a faster client on the server.
______________________________________________________________________
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
http://www.slug.org.au/etherboot/ 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 $60 pentium 75
2.2. Documentation
You may like to familiarise yourself with the linux documentation,
specifically you can read (skim) for an overview the following :
o /usr/doc/HOWTO/mini/Diskless - a similar howto tackling this
problem
o Networking Overview HOWTO - Networking capabilities of the Linux
o Ethernet HOWTO - Information on Ethernet hardware compatibility
o NET-3 HOWTO - How to configure TCP/IP networking under Linux.
Also you probably have in the /usr/doc/LDP/ directory
o The System Administrators' Guide
o The Network Administrators' Guide
o Linux Installation and Getting Started
The obligitory link
o http://www.magma.ca/~bklimas help for new linux users.
One last thing
o my network server is snoball , my client is elite and my
(local)domain is gundog.net Replace with your computers names where
applicable
3. Server setup
The server needs to be setup in readiness for the client in a number
of ways
3.1. Check your network services on your server
run the command /sbin/ifconfig if your output is similar to below then
your loopback and ethernet card are correctly configured.
______________________________________________________________________
[cassie@snoball cassie]$ /sbin/ifconfig
lo Link encap:Local Loopback
inet addr:127.0.0.1 Bcast:127.255.255.255 Mask:255.0.0.0
UP BROADCAST LOOPBACK RUNNING MTU:3584 Metric:1
RX packets:854 errors:0 dropped:0 overruns:0 frame:0
TX packets:854 errors:0 dropped:0 overruns:0 carrier:0
collisions:0
eth0 Link encap:Ethernet HWaddr 00:AA:00:BB:BD:09
inet addr:192.168.53.1 Bcast:192.168.53.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
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
setup)
___________________________________________________________________
#/etc/dhcpd.conf
subnet 192.168.35.0 netmask 255.255.255.0 {
option domain-name "gundog.net";
range dynamic-bootp 192.168.35.128 192.168.35.255;
default-lease-time 21600;
max-lease-time 43200;
}
host 286 {
filename "/tftpboot/kermit.nb";
hardware ethernet 00:80:c8:22:ae:de;
fixed-address 192.168.35.70;
}
host elite {
filename "/tftpboot/vmlinuz.xterm";
hardware ethernet 00:00:79:80:34:c9;
fixed-address 192.168.35.23;
option host-name "elite";
___________________________________________________________________
o the /etc/hosts file resolves IP numbers into host names
___________________________________________________________________
#etc/hosts
127.0.0.1 localhost localhost.localdomain
192.168.53.1 snoball snoball.gundog.net
192.168.53.23 elite elite.gundog.net
___________________________________________________________________
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
line
___________________________________________________________________
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 :
______________________________________________________________________
#hosts.deny
# all except those in hosts.allow
ALL:ALL
#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
drivers.
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
______________________________________________________________________
#/etc/exports
/tftpboot/elite elite(rw,no_root_squash)
/tftpboot/elite gordon(rw,no_root_squash)
/usr *.gundog.net(ro)
/home *.gundog.net(rw)
/mnt/cdrom (ro)
run exportfs -a to reread the exports file after
changes /usr/sbin/exportfs --help
#/etc/sysconfig/network
NETWORKING=yes
FORWARD_IPV4="no"
HOSTNAME="snoball" <-----------
GATEWAYDEV=""
GATEWAY=""
#/etc/sysconfig/network-scripts/ifcfg-eth0
IPADDR="192.168.53.1" <-----------
BOOTPROTO=none
______________________________________________________________________
5.2. client specific
______________________________________________________________________
#tftpboot/elite/etc/fstab
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
#tftpboot/elite/etc/sysconfig/network
NETWORKING=yes
FORWARD_IPV4=nomore
HOSTNAME=elite
GATEWAYDEV=
GATEWAY="192.168.53.1" <-----------
#/tftpboot/elite/etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
USERCTL=yes
ONBOOT=yes
BOOTPROTO=none
BROADCAST=192.168.53.255
NETWORK=192.168.53.0
NETMASK=255.255.255.0
IPADDR=192.168.53.23 <-----------
______________________________________________________________________
#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 (eg.ls
*Setup*)
o X Font Server
___________________________________________________________________
#chech how xfs starts on server /etc/rc.d/init.d/xfs
start)
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
echo
;;
#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.
#etc/inittab
id:5:initdefault:
and
# 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.
______________________________________________________________________
#/tftpboot/elite/etc/inittab
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 bigfoot.com
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