Dynamic Host Configuration Protocol. DHCP allows you to place machines on a network and configure many of their settings (network-wise) via a server that your host machine queries. Usually this is limited to what IP and DNS client information a host uses on the network, and this greatly increases an administrator's ability to configure a large number of hosts to use a network with minimal effort (as opposed to configuring each host individually.)
The service daemon on most *nix platforms is called dhcpd, the client application (if your *nix box is set up to use DHCP,) is usually dhclient.
The most common unix implementation of the DHCP service is the ISC's DHCP; Microsoft has their own implementation, as does Sun Microsystems.
(placeholder...needs info on hosts, networks, shared-networks and the different options)
Problems starting dhcpd
Errors when trying to start
NOTE: This problem was found on this architecture, but may apply to others.
dhcp-1# uname -a FreeBSD dhcp-1.one.example.com 6.0-RELEASE FreeBSD 6.0-RELEASE #0: Thu Nov 3 09:36:13 UTC 2005 email@example.com:/usr/obj/usr/src/sys/GENERIC i386 dhcp-1#
dhcp-1# /usr/local/etc/rc.d/isc-dhcpd.sh start chown: dhcpd: Invalid argument /usr/local/etc/rc.d/isc-dhcpd.sh: WARNING: unable to change permissions of /var/run/dhcpd /usr/local/etc/rc.d/isc-dhcpd.sh: WARNING: safe_run: chown dhcpd:dhcpd /var/db/dhcpd /usr/local/etc/rc.d/isc-dhcpd.sh: WARNING: unable to change permissions of /var/db/dhcpd chown: dhcpd: Invalid argument /usr/local/etc/rc.d/isc-dhcpd.sh: WARNING: unable to change permissions of /var/db/dhcpd/dhcpd.leases Starting dhcpd. dhcp-1#
Find out if dhcpd is running
dhcp-1# ps -auwx | grep dhcp root 94818 0.0 0.6 2188 1536 ?? Is 15Jan07 0:00.05 /usr/local/sbin/dhcpd root 24289 0.0 1.1 3892 2612 p0 RV 6:22AM 0:00.00 grep dhcp (csh)
Stop dhcpd (if running)
dhcp-1# kill -9 94818
Verify that dhcpd has been stopped
dhcp-1# ps -auwx | grep dhcp root 24293 0.0 0.1 348 208 p0 R+ 6:22AM 0:00.00 grep dhcp
Fix the problem
dhcp-1# /usr/local/etc/rc.d/isc-dhcpd.sh install Added group "dhcpd". Added user "dhcpd". dhcp-1#
Start dhcpd normally
dhcp-1# /usr/local/etc/rc.d/isc-dhcpd.sh start Starting dhcpd. dhcp-1#