Chapter 23. Dynamic Host Configuration Protocol (DHCP)230• -d — Log the DHCP server daemon to the standard error descriptor. This is mostly used fordebugging. If this is not specified, the log is written to /var/log/messages.• -cf — Specify the location of the configuration file. The default location is /etc/dhcpd.conf.• -lf — Specify the location of the lease database file. If a lease database file alreadyexists, it is very important that the same file be used every time the DHCP server is started. It isstrongly recommended that this option only be used for debugging purposes on non-productionmachines. The default location is /var/lib/dhcp/dhcpd.leases.• -q — Do not print the entire copyright message when starting the daemon.23.2.4. DHCP Relay AgentThe DHCP Relay Agent (dhcrelay) allows for the relay of DHCP and BOOTP requests from a subnetwith no DHCP server on it to one or more DHCP servers on other subnets.When a DHCP client requests information, the DHCP Relay Agent forwards the request to the list ofDHCP servers specified when the DHCP Relay Agent is started. When a DHCP server returns a reply,the reply is broadcast or unicast on the network that sent the original request.The DHCP Relay Agent listens for DHCP requests on all interfaces unless the interfaces are specifiedin /etc/sysconfig/dhcrelay with the INTERFACES directive.To start the DHCP Relay Agent, use the command service dhcrelay start.23.3. Configuring a DHCP ClientThe first step for configuring a DHCP client is to make sure the kernel recognizes the network interfacecard. Most cards are recognized during the installation process and the system is configured to usethe correct kernel module for the card. If a card is added after installation, Kudzu1 should recognizeit and prompt for the configuration of the corresponding kernel module for it. Be sure to check theHardware Compatibility List available at http://hardware.redhat.com/hcl/. If the network card is notconfigured by the installation program or Kudzu and you know which kernel module to load for it, referto Chapter 37, Kernel Modules for details on loading kernel modules.To configure a DHCP client manually, modify the /etc/sysconfig/network file to enablenetworking and the configuration file for each network device in the /etc/sysconfig/network-scripts directory. In this directory, each device should have a configuration file named ifcfg-eth0, where eth0 is the network device name.The /etc/sysconfig/network file should contain the following line:NETWORKING=yesThe NETWORKING variable must be set to yes if you want networking to start at boot time.The /etc/sysconfig/network-scripts/ifcfg-eth0 file should contain the following lines:Kudzu is a hardware probing tool run at system boot time to determine what hardware has been added or removed from thesystem.
