dhcpcd
dhcpcd(8) Linux System Manager's Manual dhcpcd(8)
NAME
dhcpcd - DHCP client daemon
SYNOPSIS
dhcpcd [-dknrBCDHRT] [-t timeout] [-c filename]
[-h hostname] [-i vendorClassID] [-I clientID]
[-l leasetime] [-s [ipaddr]] [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, broad
cast 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 recom
mended 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 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 sys
tem boots dhcpcd will use cache to request the same
IP address from DHCP server which was assigned
before the system went down.
-n Sends SIGALRM signal to the dhcpcd process that is
currently running which forces dhcpcd to try to
renew the lease. If dhcpcd is not running, the flag
is ignored and dhcpcd follows the normal startup
procedure.
-r Makes dhcpcd RFC1541 (obsolete) compliant. dhcpcd
is RFC2131 compliant unless this option is speci
fied.
-B Requests broadcast response from DHCP server.
-C Forces dhcpcd to calculate checksum on received
packets.
-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 Test case, when dhcpcd goes through the DHCP nego
tiation sequence but doesn't actually configure the
interface or otherwise change anything on the sys
tem. Used primarily for testing DHCP servers.
-t timeout
Specifies (in seconds ) for how long dhcpcd will
try to get an IP address. The default is 60 sec
onds. 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 contain
ing 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).
-s [ipaddr]
Sends DHCP_INFORM message to DHCP server using
ipaddr. The optional ipaddr parameter must be in
the form xxx.xxx.xxx.xxx. If no ipaddr parameter
is given on the command line dhcpcd will use the IP
address currently assigned to the interface. If
there is no IP address currently assigned to the
interface dhcpcd will use previously obtained IP
address stored in /etc/dhcpc/dhcpcd-<inter
face>.cache file.
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.
SEE ALSO
Dynamic Host Configuration Protocol, RFC2131 and RFC1541
(obsolete) DHCP Options and BOOTP Vendor Extensions,
RFC2132
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.
AUTHORS
v.<1.3
Yoichi Hariguchi <yoichi@fore.com>
v.1.3
Sergei Viznyuk <sv@phystech.com>
dhcpcd 1.3 31 January 1998 dhcpcd(8)
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