One free software DHCP server is ISC dhcpd. In Debian GNU/Linux, this is available in the dhcp package. Here is a sample configuration file for it (usually /etc/dhcpd.conf):

option domain-name "example.com";
option domain-name-servers ns1.example.com;
option subnet-mask 255.255.255.0;
default-lease-time 600;
max-lease-time 7200;
server-name "servername";

subnet 192.168.1.0 netmask 255.255.255.0 {
  range 192.168.1.200 192.168.1.253;
  option routers 192.168.1.1;
}

host clientname {
  filename "/tftpboot/tftpboot.img";
  server-name "servername";
  next-server servername;
  hardware ethernet 01:23:45:67:89:AB; 
  fixed-address 192.168.1.90;
}

Note: the new (and preferred) dhcp3 package uses /etc/dhcp3/dhcpd.conf.

In this example, there is one server "servername" which performs all of the work of DHCP, server, TFTP server, and network gateway. You will almost certainly need to change the domain-name options, as well as the server name and client hardware address. The "filename" option should be the name of the file which will be retrieved via TFTP.

After you have edited the dhcpd configuration file, restart it with /etc/init.d/dhcpd restart.

To get the TFTP server ready to go, you should first make sure that tftpd is enabled. This is usually enabled by having something like the following line in /etc/inetd.conf:

tftp dgram udp wait nobody /usr/sbin/tcpd in.tftpd /tftpboot

Debian packages will in general set this up correctly by default when they are installed.

Look in that file and remember the directory which is used as the argument of in.tftpd; you'll need that below. The -l argument enables some versions of in.tftpd to log all requests to the system logs; this is useful for diagnosing boot errors. If you've had to change /etc/inetd.conf, you'll have to notify the running inetd process that the file has changed. On a Debian machine, run /etc/init.d/inetd reload; on other machines, find out the process ID for inetd, and run kill -HUP inetd-pid.

If you intend to install Debian on an SGI machine and your TFTP server is a GNU/Linux box running Linux 2.4, you'll need to set the following on your server:

# echo 1 > /proc/sys/net/ipv4/ip_no_pmtu_disc

to turn off Path MTU discovery, otherwise the Indy's PROM can't download the kernel. Furthermore, make sure TFTP packets are sent from a source port no greater than 32767, or the download will stall after the first packet. Again, it's Linux 2.4.X tripping this bug in the PROM, and you can avoid it by setting

# echo "2048 32767" > /proc/sys/net/ipv4/ip_local_port_range

to adjust the range of source ports the Linux TFTP server uses.

Next, place the TFTP boot image you need, as found in Section 4.2.1, “Where to Find Installation Images”, in the tftpd boot image directory. Generally, this directory will be /tftpboot. You'll have to make a link from that file to the file which tftpd will use for booting a particular client. Unfortunately, the file name is determined by the TFTP client, and there are no strong standards.