0. Introduction This is an RFC2131,RFC2132, and RFC1541 compliant DHCP client daemon. RFC1541 was obsoleted by RFC2131, but there are still some RFC1541 compliant DHCP servers. dhcpcd gets an IP address and other information from a corresponding DHCP server, configures the network interface automatically, and tries to renew the lease time according to RFC2131 or RFC1541 depending on the command line option. 1. Install Make sure your kernel is compiled with support for SOCK_PACKET (CONFIG_PACKET option). Cd to source distribution directory. Do ./configure --prefix=/ Please note the GNU default installation --prefix=/usr/local is not what most users want for dhcpcd installation. Edit Makefile to customize compile time options. Do 'make' followed by 'make install'. To enable dhcpcd error logging add the following line to your /etc/syslog.conf file: local0.* /var/log/dhcpcd.log and then refresh syslogd daemon: kill -1 `cat /var/run/syslogd.pid` Note If you replace your network card or upgrade to a different version of dhcpcd you might not be able to obtain the same old IP address from DHCP server. This is because the DHCP server identifies clients by ClientID DHCP option which by default is MAC address of the network card. The work around is to use -I ClientID option with some unique "ClientID" string. Also, upgrading to a different version of dhcpcd invalidates *.cache file where dhcpcd stores IP address which it tries to renew on restart. 2. How to Use It Invoke the client by typing 'dhcpcd'. Note you should NOT explicitly put it in the background with the '&' character - background processing is automatic unless 'dhcpcd' was compiled with -DDEBUG flag. Dhcpcd will fork into background as soon as it configures the interface. By default, dhcpcd will attach to 'eth0' unless you explicitly give an interface name on the command line. The example below demonstrates dhcpcd usage in a case where linux box serves as a router/firewall for the local network 192.168.12.0. if dhcpcd eth1; then inetd /usr/sbin/sendmail -bd httpd echo 1 > /proc/sys/net/ipv4/ip_forward modprobe ip_tables modprobe iptable_nat modprobe iptable_filter modprobe ipt_MASQUERADE modprobe ip_nat_ftp modprobe ip_conntrack_ftp iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE else echo "**** Unable to configure eth0" fi The bootup process will wait until 'dhcpcd' configures interface or until dhcpcd times out before proceeding further. Any time dhcpcd configures or shuts down interface it will try to execute /etc/dhcpc/dhcpcd.exe script with appropriate parameters passed. The exact pathname of the executable script can be changed with "-c ExecFilePath" dhcpcd option. The directory can be specified with "-L " option, otherwise it defaults to /etc/dhcpc/. The dhcpcd.exe script invokation is: /etc/dhcpc/dhcpcd.exe [-d] where is actually /dhcpcd-.info file; optional parameter [-d] is a debug flag passed if dhcpcd has been invoked with -d flag. The second parameter to dhcpcd.exe script is "up" if the interface has been configured with the same IP address as before reboot, "down" if the interface has been shut down, "new" if the interface has been configured with new IP address. 3. Supported DHCP Options The current version of dhcpcd supports the following DHCP options: o lease time o renewal (T1) time o rebind (T2) time o netmask o broadcast address o router o dns o host name o domain name o nis domain name o nis servers o ntp servers o static routes 5. Cache File dhcpcd saves the assigned IP address into the file /var/cache/dhcpcd-.cache (the word is actually replaced with the interface name like eth0, etc. to which dhcpcd is attached) so that it can try to use that IP address when it is invoked next time. Remove the file /var/cache/dhcpcd-.cache before you invoke dhcpcd unless you like using the previously assigned IP address. 6. Information File dhcpcd writes the configuration information into /var/cache/dhcpcd-.info file. The word is actually replaced with the interface name like eth0, etc. to which dhcpcd is attached. That file may be included into a Bourne or Korn shell script to set an environment variables like e.g. HOSTNAME, DOMAIN, NETMASK, etc. The supplied sample /dhcpcd.exe script demonstrates usage of /dhcpcd-.info file. 7. Other Information dhcpcd sends DHCP_RELEASE message to the DHCP server, deletes the /var/cache/dhcpcd-.cache file and brings the attached network interface down when it gets SIGHUP signal. It will not send DHCP_RELEASE message and will not delete /dhcpcd-.cache file in a case it gets SIGTERM as normally happens upon reboot. dhcpcd may be used to obtain multiple IP addresses for the same dummy interface providing one invokes dhcpcd with -I ClientID -L ConfigDir -T -c ExecFilePath options where ClientID and ConfigDir are unique to each of the requested IP addresses. The same way it can be used to obtain IP addresses for virtual interfaces, e.g. eth0:1 dhcpcd currently supports only Ethernet link protocol. 8. In case dhcpcd does not work: Run 'dhcpcd -d' and mail me the relevant messages from /var/log/dhcpcd.log file. Also run tcpdump -evvn -i eth0 and mail the results of that. If the things are too bad for you, reconfigure with the --enable-debug option and recompile 'dhcpcd'. Run 'dhcpcd -d' and mail what you see.