dhcpconf - Controller for DHCP client configuration
/usr/sbin/dhcpconf [-d] [-f] [-s] [-a server_ip] [-w seconds] interface
start | drop | release
/usr/sbin/dhcpconf [interface] dns | domain | gateways | hostname | nis |
Directs all DHCP protocol messages to the given IP address. Currently
-d Starts DHCP only if the interface is down.
-s Starts the DHCP client daemon, joinc, if not already running. This
option is implied by the start command.
Instructs dhcpconf to wait for the time specified (if positive) or for-
ever (if negative), or until the operation completes or fails. This
option is only relevant on operations which cannot complete immedi-
ately. If the timer expires while the operation is in progress,
dhcpconf exits with a failure code, but the operation continues. If
the user specifies a finite wait interval it should, for consistency,
be at least equal to the sum of the timeout values for exponential
backoff in the startup file, /etc/join/client.pcy.
-f This option is only relevant on the start command. When an interface is
started, joinc sends DHCP discover packets using the exponential back-
off and retransmission intervals given in the /etc/join/client.pcy
file. If no reply is received at the end of this cycle, the client
replies to the controller with failure. When this option is in effect,
joinc continues trying to contact a DHCP server forever, either by
retrying the whole backoff cycle or using the last timeout value in the
array. See client.pcy(4) for details.
Puts the interface specified under control of DHCP. The joinc server
commences the DHCP on the interface. Fine tuning of this process is
provided by parameters in the startup file /etc/join/client.pcy.
Makes joinc take the interface down and transmit a DHCP release message
to the DHCP server that the IP address assigned to the interface is no
longer needed. The server is permitted to reassign the IP address to
Tells the client daemon that it should relinquish control of the inter-
face. The options to drop and release the interface are subtly dif-
ferent. Release is part of the DHCP protocol; drop is not. Drop tells
DHCP that its services for the interface in question are no longer
required -- DHCP will not try to renew the lease on the IP address and
if the lease should expire no action will be taken. This violates the
protocol and is not recommended, except for testing.
The dhcpconf command and its companion joinc implement the client side of
the Dynamic Host Configuration Protocol, DHCP. The responsibilities of
dhcpconf are as follows:
+ Control invocation and termination of DHCP on the client's hardware
+ Provide a mechanism for rendezvous with the transactions of DHCP which
are proceeding asynchronously with respect to the client boot.
All invocations of dhcpconf send instructions or requests to joinc, which
is listening at a well known port number on the Internet Protocol loopback
address. Unless the -w option is given, dhcpconf expects an immediate
reply, and exits immediately with a success or failure code, depending upon
the reply received. When the request is one which the client is unable to
fulfill immediately, the reply acknowledges that the request has been vali-
dated and that the client will initiate the task required. With the excep-
tion of start, which implicitly starts the client daemon, dhcpconf exits
with a failure code if joinc is not already running. When the -w option is
given, dhcpconf waits for the requested operation either to complete, fail,
or wait for the number of seconds specified in the following argument. When
the timer expires, dhcpconf exits with a failure code, but the operation
The dhcpconf commands are divided into two groups: start, release, and
drop initiate and terminate DHCP control of an interface. The remainder
request dhcpconf to configure the host-wide parameters or service speci-
fied, according to DHCP supplied data. The latter do not, in general, need
an interface to be specified, except in the circumstance that different
interfaces receive different configurations (See NOTES).
When two or more interfaces are configured by DHCP, the possibility exists
that the configurations received may differ. This is the norm for interface
specific parameters, but for parameters that pertain to the host as a
whole, questions of interpretation arise. List items, in particular, may
differ for example, the default gateways. When configuring services,
dhcpconf will not merge data from different interfaces. Rather only a sin-
gle interface is consulted, which, unless given on the command line, is the
first one in dhcpconf program's internal array, which is configured when
the request is made.
A cluster member should never be a DHCP client. It should always use static
If a cluster is to support a DHCP server, there can only be one DHCP server
for all the cluster members using a common database with failover.
DHCP client is not supported on dataless clients.
Exit codes are as follows:
2 DHCP was not successful. The DHCP client daemon may not be running, the
interface might have failed to configure, or no satisfactory DHCP
responses were received.
3 Bad arguments.
4 A timer was set (with -w) and the interface had not configured before
5 Can only be run as root.
6 Some system error (should never occur)
Commands: dhcpparm(8), joinc(8), showdhc(8), shleases(8)