dhcpcd

Section: Linux System Manager's Manual (8)
Updated: 31 January 1998
Index Return to Main Contents

NAME

dhcpcd - DHCP client daemon

SYNOPSIS

dhcpcd [-dkrDHR] [-t timeout] [-c filename] [-h hostname] [-i vendorClassID] [-I clientID] [-l leasetime] [interface]

DESCRIPTION

dhcpcd is an implementation of the DHCP client specified in RFC2131 (when -r option is not specified) and RFC1541 (when -r option is specified).

It gets the host information (IP address, netmask, broadcast address, etc.) from a DHCP server and configures the network interface of the machine on which it is running. It also tries to renew the lease time according to RFC2131 or RFC1541 (obsolete).

OPTIONS

-d: With this flag dhcpcd will syslog(LOG_DEBUG,...) messages for about every step it does. It's recommended to use this option since it doesn't really produce too much output but will greatly help in resolving a problems if any.
-k: Sends a SIGHUP signal to the dhcpcd process that is currently running. If dhcpcd receives SIGHUP it will send DCHP_RELEASE message to the server and destroy dhcpcd cache. In a case dhcpcd receives SIGTERM which is normally used by shutdown(8) when rebooting the system dhcpcd will not send DHCP_RELEASE and will not destroy cache. When system boots dhcpcd will use cache to request the same IP address from DHCP server which was assigned before the system went down.
-r: Makes dhcpcd RFC1541 (obsolete) compliant. dhcpcd is RFC2131 compliant unless this option is specified.
-D: Forces dhcpcd to set domainname of the host to the domainname option supplied by DHCP server. By default dhcpcd will NOT set domainname of the host to the domainname option received from DHCP server.
-H: Forces dhcpcd to set hostname of the host to the hostname option supplied by DHCP server. By default dhcpcd will NOT set hostname of the host to the hostname option received from DHCP server.
-R: Prevents dhcpcd from replacing existing /etc/resolv.conf file.
-t timeout: Specifies (in seconds ) for how long dhcpcd will try to get an IP address. The default is 60 seconds. dhcpcd will not fork into background until it gets a valid IP address in which case dhcpcd will return 0 to the parent process. In a case dhcpcd times out before receiving a valid IP address from DHCP server dhcpcd will return exit code 1 to the parent process.
-c filename: Deprecated option provided for compatibility with dhcpcd v.0.70. dhcpcd will try to execute filename after it configures the interface.
-h hostname: specifies a string used for the hostname option field when dhcpcd sends DHCP messages. Some DHCP servers require the hostname option field containing a specific string in the DHCP messages from clients.
-i vendorClassID: Specifies the vendor class identifier string. dhcpcd uses the default vendor class identifier string (system name, sytem release, and machine type) if it is not specified.
-I clientID: Specifies the client identifier string. dhcpcd uses the default client identifier (Ethernet Address of the network interface) if it is not specified.
-l leasetime: Specifies (in seconds) the recommended lease time to the server. (Note that the server can override this value if it sees fit). This value is used in the DHCP_DISCOVER message. The default is infinite (0xffffffff).
interface: Specifies the network interface name (eth0, eth1, etc.). dhcpcd uses the network interface eth0 unless an explicit name is specified.

FILES

/etc/dhcpc: directory used for storing files created by dhcpcd
/etc/dhcpc/dhcpcd-<interface>.info: file in which dhcpcd saves the host information. The word interface is actually replaced with the network interface name like eth0 to which dhcpcd is attached.
/etc/dhcpc/dhcpcd-<interface>.exe: file which dhcpcd will try to execute whenever it detects a change in IP address.
/etc/resolv.conf: file created by dhcpcd when the client receives DNS and domain name options. The old /etc/resolv.conf file will be renamed to /etc/resolv.conf.sv and will be restored back when dhcpcd exits for any reason.
/var/run/dhcpcd-<interface>.pid: file containing the process id of dhcpcd. The word interface is actually replaced with the network interface name like eth0 to which dhcpcd is attached.
/etc/dhcpc/dhcpcd-<interface>.cache: Cache file containing the previously assigned IP address and some other things. The word interface is actually replaced with the network interface name like eth0 to which dhcpcd is attached.

BUGS

dhcpcd uses time(3) to calculate the lease expiration time. If the system time is changed while the client is running, the lease expiration time may not be predictable.

dhcpcd does not support the DHCP_INFORM message.

dhcpcd cannot handle DHCP options (e.g. domain name) which have more than 255 characters. All the DHCP options have to be less than or equal to 255.

AUTHORS

v.<1.3

Yoichi Hariguchi <yoichi@fore.com>

v.1.3

Sergei Viznyuk <sv@phystech.com>

▲このページのトップへ