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dhcpconf(8)							  dhcpconf(8)



NAME

  dhcpconf - Controller	for DHCP client	configuration

SYNOPSIS

  /usr/sbin/dhcpconf [-d] [-f] [-s] [-a	server_ip] [-w seconds]	interface
  start	| drop | release

  /usr/sbin/dhcpconf [interface] dns | domain |	gateways | hostname | nis |
  routes

OPTIONS

  -a server_ip
      Directs all DHCP protocol	messages to the	given IP address.  Currently
      not implemented.

  -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.

  -w seconds
      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.

  start
      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.

  release
      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
      another client.

  drop
      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.

DESCRIPTION

  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
       interface(s).

    +  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
  requested continues.

  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).

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.

RESTRICTIONS

  A cluster member should never	be a DHCP client. It should always use static
  addressing.

  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 STATUS

  Exit codes are as follows:

  0   Success.

  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
      it expired.

  5   Can only be run as root.

  6   Some system error	(should	never occur)

SEE ALSO

  Commands: dhcpparm(8), joinc(8), showdhc(8), shleases(8)

  Files: client.pcy(4)

  Information: DHCP(7)