UWMLSC > Beowulf Systems > Medusa

DHCP Configuration

This page describes how to set up the DHCP configuration file on the master to add new nodes.

The slave nodes get their network configuration from the master when they boot up by sending DHCP requests with their ethernet hardware adderess. The master responds with information about the slaves IP address and other network configuaration. The actual network configuration is performed using the dhcpcd (8) program. See the dhcpcd man page for more details on its operation.

There should be no need to change the network configuration on the slave side ; all the changes should be done on the master. Make sure that if you add a new slave, it has an entry in the DHCP configuration file on the master before it is booted.

For more information on DHCP see the man pages dhcpd (8) and dhcpd.conf (5)

This configuration file resides in the CVS archive under 7.3install/masterconfig/master001/configfiles/etc/dhcpd.conf

The structure of the file is as follows:

Global Parameter Section

option subnet-mask255.255.254.0;
option domain-name"medusa.phys.uwm.edu";
option domain-name-servers129.89.201.231,;
option ntp-servers129.89.201.231,;

The global parameters describe network options common to all slaves and should not be changed. The subnet mask is set to to allow the two class C subnets and to be used as a single subnet.

The domain name for all the slaves is medusa.phys.uwm.edu

The default domain name server is the primary master (medusa, master001). The secondary master (hydra, master002) is provided as a backup.

The primary and secondary masters are used as an NTP server, although this value is overridden by the configuraion in /etc/ntp.conf (This uses both the master nodes).

Internal Group Section

This section is the important section of the file. This is a short example showing slaves s001, s002, and s241.

subnet netmask {
group {
 filename "pxelinux.0";
 host medusa-slave001 {
  hardware ethernet 00:03:47:8a:c8:2d;
 host medusa-slave002 {
  hardware ethernet 00:03:47:9c:4e:ed;
 host medusa-slave241 {
  hardware ethernet 00:03:47:9c:4c:f2;

To add a new node to the system, you must know its hardware ethernet address (MAC address). You also need to decide what its IP address is going to be according to the scheme shown in the IP address page.

As an example, say the machine has MAC address aa:bb:cc:dd:ee:ff and you wish to add it as slave 250. The machine's IP address will be . To add the slave add the lines:

 host medusa-slave250 {
  hardware ethernet aa:bb:cc:dd:ee:ff;

Although the order of the entries within the group does not matter, you should keep the file in order by increasing IP address for easy management. In this case, the above entry for slave 250 would go after that of slave 241.

External Subnet Section

subnet netmask {

The last section of the file should not be touched. It is empty to that DHCPd does not attempt to serve IP addresses on the physics department subnet.

$Id: dhcp_configuration.html,v 1.1 2004/06/01 16:38:52 parmor Exp $

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