dhcpconf(8)dhcpconf(8)NAMEdhcpconf - 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
Directs all DHCP protocol messages to the given IP address. Currently
not implemented. Starts DHCP only if the interface is down. 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 forever (if negative), or until the opera‐
tion completes or fails. This option is only relevant on operations
which cannot complete immediately. If the timer expires while the oper‐
ation is in progress, dhcpconf exits with a failure code, but the oper‐
ation 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. This option is only relevant on the start com‐
mand. When an interface is started, joinc sends DHCP discover packets
using the exponential backoff 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 another
client. Tells the client daemon that it should relinquish control of
the interface. The options to drop and release the interface are subtly
different. 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 ren‐
dezvous with the transactions of DHCP which are proceeding asyn‐
chronously 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 validated and that the client will initiate the
task required. With the exception 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 contin‐
ues.
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 specified, according to DHCP supplied data. The latter do not,
in general, need an interface to be specified, except in the circum‐
stance 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 config‐
uring services, dhcpconf will not merge data from different interfaces.
Rather only a single 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: Success. 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. Bad argu‐
ments. A timer was set (with -w) and the interface had not configured
before it expired. Can only be run as root. Some system error (should
never occur)
SEE ALSO
Commands: dhcpparm(8), joinc(8), showdhc(8), shleases(8)
Files: client.pcy(4)
Information: DHCP(7)dhcpconf(8)