Thin Clients

Overview

This outlines my local system and how to configure things to enable new code to be downloaded to the T20.

Whilst it is possible to just do things on a single Windows computer, having a separate Linux system does have its benefits. Many Linux distributions will run quite happily on old computers that have been 'retired' thanks to the increasing demands on computing power that each new release of Windows seems to require. Alternatively you can use VMware or the Microsoft Virtual PC to run more than one operating system on your main PC.

Environment

I'm connected to my ISP via Netgear router. This provides wired and wireless connections to an internal LAN with a local address space of 192.168.10.xxx. The router's address is 192.168.10.1. The Netgear router acts as a DHCP server and provides DNS via the ISP's servers. My main computer is a Windows XP system and I have a separate Linux box currently running Fedora Core 10.

For some reason the Netgear router does not register the names of my various boxes other than my main Windows (XP) PC. Others all appear as "unknown" on its list of connections and so it is not possible to reach them by name. I spent a little while trying to resolve this and then gave up. I configured the Netgear box to always issue a fixed IP address (192.168.10.6) to the Linux box. (Simple table entry against the MAC address).

User

On the Linux box I created a new user thin and within that home directory a directory EvoT20 for the work on the T20. Any software build for network download ends up in /home/thin/bin/.

Server Software

As described elsewhere we need run a DHCP server and a TFTP server to respond to the requests from the T20. Using the standard menu system on the Fedora desktop I went into system->administration and ran the add/remove software application. Under servers I selected:

dhcp (Dynamic Host Configuration Protocol) relay and user agent
dhcp12:4.0.0.33.fc10 (i386)

and

The server for the Trivial File Transfer Protocol (TFTP)
tftp-server-0.48-6.fc10 (i386)

and then hit update.

Once installed they need to be configured.

DHCP Server

By default the DHCP server uses the configuration file /etc/dhcpd.conf. I edited this to:

# dhcpd.conf
#
# Sample configuration file for ISC dhcpd
#

default-lease-time 120;
max-lease-time 120;
server-name "turtle";
option domain-name-servers 192.168.10.1;

# Use this to send dhcp log messages to a different log file (you also
# have to hack syslog.conf to complete the redirection).
log-facility local7;

# This is a very basic subnet declaration.

subnet 192.168.10.0 netmask 255.255.255.0 {
 local-port 10067;
 range dynamic-bootp 192.168.10.200 192.168.10.240;
 option routers 192.168.10.1;
 filename "bootp.bin";
 next-server 192.168.10.6;
}

(turtle is the name of my Linux box). As the Netgear router doesn't recognise turtle as a local host we add the actual IP address in the next-server configuration field.

TFTP Server

The TFTP daemon normally runs under xinetd, but when I tried this I found I was unable to specify the ports that it uses without editing the system file /etc/services which I preferred to leave untouched. The -a switch only seems to work in conjunction with the -l switch (run a local copy) so I gave up the idea of having it started via the standard services and xinetd.

Starting the servers

I use a very simple script which lacks the sophistication of the netxfer.sh from Karl Mowatt-Wilson. Mine is just:

#!/bin/sh
dhcpd -p 10067
in.tftp -l -a:10069 -s /home/thin/bin

Links

Other detail can be found here on the Open-EvoT20 web site.

Any comments? email me. Last update April 2009

Evo T20: Development Environment