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* $FreeBSD$ id, obrien copyright.
  * Document the -D option. (r1.6)
  * Correct man page reference and fix typo. (r1.8)

Reviewed by: obrien
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Murray Stokely 2002-02-19 12:00:47 +00:00
parent 92c4d51b6d
commit 5e84f73d96
1 changed files with 184 additions and 83 deletions
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267
contrib/isc-dhcp/client/dhclient.8
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@ -1,40 +1,20 @@
.\" dhclient.8
.\"
.\" Copyright (c) 1997 The Internet Software Consortium.
.\" All rights reserved.
.\" Copyright (c) 1996-1999 Internet Software Consortium.
.\" Use is subject to license terms which appear in the file named
.\" ISC-LICENSE that should have accompanied this file when you
.\" received it. If a file named ISC-LICENSE did not accompany this
.\" file, or you are not sure the one you have is correct, you may
.\" obtain an applicable copy of the license at:
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" http://www.isc.org/isc-license-1.0.html.
.\"
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of The Internet Software Consortium nor the names
.\" of its contributors may be used to endorse or promote products derived
.\" from this software without specific prior written permission.
.\" This file is part of the ISC DHCP distribution. The documentation
.\" associated with this file is listed in the file DOCUMENTATION,
.\" included in the top-level directory of this release.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
.\" CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
.\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
.\" DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
.\" CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
.\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
.\" USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
.\" ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
.\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" This software has been written for the Internet Software Consortium
.\" by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
.\" Enterprises. To learn more about the Internet Software Consortium,
.\" see ``http://www.isc.org/isc''. To learn more about Vixie
.\" Enterprises, see ``http://www.vix.com''.
.\" Support and other services are available for ISC products - see
.\" http://www.isc.org for more information.
.\"
.\" Portions copyright (c) 2000 David E. O'Brien.
.\" All rights reserved.
@ -46,23 +26,56 @@ dhclient - Dynamic Host Configuration Protocol Client
.SH SYNOPSIS
.B dhclient
[
.B -Ddq1
.B -p
.I port
]
[
.B -cf
.I config-file
.B -D
]
[
.B -d
]
[
.B -q
]
[
.B -1
]
[
.B -r
]
[
.B -lf
.I lease-file
]
[
.B -p
.I port
.B -pf
.I pid-file
]
[
.B -pf
.I pidfile
.B -cf
.I config-file
]
[
.B -sf
.I script-file
]
[
.B -s
server
]
[
.B -g
relay
]
[
.B -n
]
[
.B -nw
]
[
.B -w
]
[
.I if0
@ -104,7 +117,7 @@ dhclient.leases file. In order to prevent the file from becoming
arbitrarily large, from time to time dhclient creates a new
dhclient.leases file from its in-core lease database. The old version
of the dhclient.leases file is retained under the name
.IR dhcpd.leases~
.IR dhclient.leases~
until the next time dhclient rewrites the database.
.PP
Old leases are kept around in case the DHCP server is unavailable when
@ -129,9 +142,16 @@ than cycling through the list of old leases.
.PP
The names of the network interfaces that dhclient should attempt to
configure may be specified on the command line. If no interface names
are specified on the command line dhclient will identify all network
interfaces, elimininating non-broadcast interfaces if possible, and
attempt to configure each interface.
are specified on the command line dhclient will normally identify all
network interfaces, elimininating non-broadcast interfaces if
possible, and attempt to configure each interface.
.PP
It is also possible to specify interfaces by name in the
.B dhclient.conf(5)
file. If interfaces are specified in this way, then the client will
only configure interfaces that are either specified in the
configuration file or on the command line, and will ignore all other
interfaces.
.PP
The
.B -D
@ -142,70 +162,151 @@ to save the script it creates for use in conjunction with
in
.IR /tmp.
.PP
Dhclient will normally run in the foreground until it has configured
an interface, and then will revert to running in the background.
To run force dhclient to always run as a foreground process, the
.B -d
flag should be specified. This is useful when running dhclient under
a debugger, or when running it out of inittab on System V systems.
.PP
If dhclient should listen and transmit on a port other than the
If the DHCP client should listen and transmit on a port other than the
standard (port 68), the
.B -p
flag may used. It should be followed by the udp port number that
dhclient should use. This is mostly useful for debugging purposes.
If the
.B -p
flag is specified, the client will transmit responses to servers at a
port number that is one less than the one specified - i.e., if you
specify
.B -p
68, then the client will listen on port 68 and transmit to port 67.
Datagrams that must go through relay agents are sent to the port
number specified with the
.B -p
flag - if you wish to use alternate port numbers, you must configure
any relay agents you are using to use the same alternate port numbers.
If a different port is specified for the client to listen on and
transmit on, the client will also use a different destination port -
one greater than the specified destination port.
.PP
The
.B -cf
flag may be used to change the shell script from the default of
/sbin/dhclient-script.
The DHCP client normally transmits any protocol messages it sends
before acquiring an IP address to, 255.255.255.255, the IP limited
broadcast address. For debugging purposes, it may be useful to have
the server transmit these messages to some other address. This can
be specified with the
.B -s
flag, followed by the IP address or domain name of the destination.
.PP
The
.B -lf
flag may be used to change the lease output file from the default of
/var/db/dhclient.leases.
For testing purposes, the giaddr field of all packets that the client
sends can be set using the
.B -g
flag, followed by the IP address to send. This is only useful for testing,
and should not be expected to work in any consistent or useful way.
.PP
The
.B -pf
flag may be used to change the PID file from the default of
/var/run/dhclient.pid.
The DHCP client will normally run in the foreground until it has
configured an interface, and then will revert to running in the
background. To run force dhclient to always run as a foreground
process, the
.B -d
flag should be specified. This is useful when running the client
under a debugger, or when running it out of inittab on System V
systems.
.PP
The
The client normally prints a startup message and displays the
protocol sequence to the standard error descriptor until it has
acquired an address, and then only logs messages using the
.B syslog (3)
facility. The
.B -q
flag may be used to reduce the amount of screen output from
.B dhclient.
flag prevents any messages other than errors from being printed to the
standard error descriptor.
.PP
The client normally doesn't release the current lease as it is not
required by the DHCP protocol. Some cable ISPs require their clients
to notify the server if they wish to release an assigned IP address.
The
.B -r
flag explicitly releases the current lease, and once the lease has been
released, the client exits.
.PP
The
.B -1
flag cause dhclient to try once to get a lease. If it fails, dhclient exits
with exit code two.
.PP
The DHCP client normally gets its configuration information from
.B ETCDIR/dhclient.conf,
its lease database from
.B DBDIR/dhclient.leases,
stores its process ID in a file called
.B RUNDIR/dhclient.pid,
and configures the network interface using
.B CLIENTBINDIR/dhclient-script
To specify different names and/or locations for these files, use the
.B -cf,
.B -lf,
.B -pf
and
.B -sf
flags, respectively, followed by the name of the file. This can be
particularly useful if, for example,
.B DBDIR
or
.B RUNDIR
has not yet been mounted when the DHCP client is started.
.PP
The DHCP client normally exits if it isn't able to identify any
network interfaces to configure. On laptop computers and other
computers with hot-swappable I/O buses, it is possible that a
broadcast interface may be added after system startup. The
.B -w
flag can be used to cause the client not to exit when it doesn't find
any such interfaces. The
.B omshell (8)
program can then be used to notify the client when a network interface
has been added or removed, so that the client can attempt to configure an IP
address on that interface.
.PP
The DHCP client can be directed not to attempt to configure any interfaces
using the
.B -n
flag. This is most likely to be useful in combination with the
.B -w
flag.
.PP
The client can also be instructed to become a daemon immediately, rather
than waiting until it has acquired an IP address. This can be done by
supplying the
.B -nw
flag.
.SH CONFIGURATION
The syntax of the dhclient.conf(5) file is discussed separately.
.SH OMAPI
The DHCP client provides some ability to control it while it is
running, without stopping it. This capability is provided using OMAPI,
an API for manipulating remote objects. OMAPI clients connect to the
client using TCP/IP, authenticate, and can then examine the client's
current status and make changes to it.
.PP
Rather than implementing the underlying OMAPI protocol directly, user
programs should use the dhcpctl API or OMAPI itself. Dhcpctl is a
wrapper that handles some of the housekeeping chores that OMAPI does
not do automatically. Dhcpctl and OMAPI are documented in \fBdhcpctl(3)\fR
and \fBomapi(3)\fR. Most things you'd want to do with the client can
be done directly using the \fBomshell(1)\fR command, rather than
having to write a special program.
.SH THE CONTROL OBJECT
The control object allows you to shut the client down, releasing all
leases that it holds and deleting any DNS records it may have added.
It also allows you to pause the client - this unconfigures any
interfaces the client is using. You can then restart it, which
causes it to reconfigure those interfaces. You would normally pause
the client prior to going into hibernation or sleep on a laptop
computer. You would then resume it after the power comes back.
This allows PC cards to be shut down while the computer is hibernating
or sleeping, and then reinitialized to their previous state once the
computer comes out of hibernation or sleep.
.PP
The control object has one attribute - the state attribute. To shut
the client down, set its state attribute to 2. It will automatically
do a DHCPRELEASE. To pause it, set its state attribute to 3. To
resume it, set its state attribute to 4.
.PP
.SH FILES
.B /etc/dhclient.conf, /var/db/dhclient.leases, /var/db/dhclient.leases~.
.B /var/run/dhclient.pid,
.B CLIENTBINDIR/dhclient-script,
.B ETCDIR/dhclient.conf, DBDIR/dhclient.leases, RUNDIR/dhclient.pid,
.B DBDIR/dhclient.leases~.
.SH SEE ALSO
dhclient.conf(5), dhclient.leases(5), dhclient-script(8)
dhclient.conf(5), dhclient.leases(5), dhclient-script(8).
.SH AUTHOR
.B dhclient(8)
has been written for the Internet Software Consortium
by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
by Ted Lemon in cooperation with Vixie
Enterprises. To learn more about the Internet Software Consortium,
see
.B http://www.vix.com/isc.
.B http://www.isc.org
To learn more about Vixie
Enterprises, see
.B http://www.vix.com.