98454aa775
DHCP_DECLINE now includes the IP and Server in the message. Trailing NULLs are stripped from string options. ntpd is only restarted if it is already running. ClientID is no longer sent by default. CSR comes before routers and static routes as per RFC 3442. Host routes are now added correctly. If a the interface link flaps but status does not change, do not reset the timer.
438 lines
13 KiB
Groff
438 lines
13 KiB
Groff
.\" Copyright 2006-2008 Roy Marples
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.\" All rights reserved
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.Dd November 18, 2008
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.Dt DHCPCD 8 SMM
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.Sh NAME
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.Nm dhcpcd
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.Nd an RFC 2131 compliant DHCP client
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.Sh SYNOPSIS
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.Nm
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.Op Fl bdknpqABDEGKLTV
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.Op Fl c , -script Ar script
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.Op Fl f , -config Ar file
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.Op Fl h , -hostname Ar hostname
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.Op Fl i , -vendorclassid Ar vendorclassid
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.Op Fl l , -leasetime Ar seconds
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.Op Fl m , -metric Ar metric
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.Op Fl o , -option Ar option
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.Op Fl r , -request Ar address
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.Op Fl s , -inform Ar address Ns Op Ar /cidr
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.Op Fl t , -timeout Ar seconds
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.Op Fl u , -userclass Ar class
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.Op Fl v , -vendor Ar code , Ar value
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.Op Fl C , -nohook Ar hook
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.Op Fl F , -fqdn Ar FQDN
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.Op Fl I , -clientid Ar clientid
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.Op Fl O , -nooption Ar option
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.Op Fl Q , -require Ar option
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.Op Fl X , -blacklist Ar address
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.Ar interface
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.Nm
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.Fl k , -release
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.Ar interface
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.Nm
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.Fl x , -exit
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.Ar interface
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.Sh DESCRIPTION
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.Nm
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is an implementation of the DHCP client specified in
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.Li RFC 2131 .
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.Nm
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gets the host information
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.Po
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IP address, routes, etc
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.Pc
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from a DHCP server and configures the network
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.Ar interface
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of the
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machine on which it is running.
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.Nm
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then runs the configuration script which writes DNS information to
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.Xr resolvconf 8 ,
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if available, otherwise directly to
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.Pa /etc/resolv.conf .
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If the hostname is currenly blank, (null) or localhost then
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.Nm
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sets the hostname to the one supplied by the DHCP server.
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.Nm
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then daemonises and waits for the lease renewal time to lapse.
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Then it attempts to renew its lease and reconfigure if the new lease changes.
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.Ss Local Link configuration
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If
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.Nm
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failed to obtain a lease, it probes for a valid IPv4LL address
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.Po
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aka ZeroConf, aka APIPA
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.Pc .
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Once obtained it restarts the process of looking for a DHCP server to get a
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proper address.
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.Pp
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When using IPv4LL,
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.Nm
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nearly always succeeds and returns an exit code of 0.
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In the rare case it fails, it normally means that there is a reverse ARP proxy
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installed which always defeats IPv4LL probing.
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To disable this behaviour, you can use the
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.Fl L , -noipv4ll
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option.
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.Ss Hooking into DHCP events
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.Nm
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runs
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.Pa @SCRIPT@ ,
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or the script specified by the
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.Fl c , -script
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option.
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This script runs each script found in
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.Pa @HOOKDIR@
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in a lexical order.
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The default installation supplies the scripts
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.Pa 01-test ,
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.Pa 10-mtu ,
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.Pa 20-resolv.conf
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and
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.Pa 30-hostname .
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You can disable each script by using the
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.Fl C , -nohook
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option.
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See
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.Xr dhcpcd-run-hooks 8
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for details on how these scripts work.
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.Nm
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currently ignores the exit code of the script.
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.Ss Fine tuning
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You can fine tune the behaviour of
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.Nm
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with the following options:
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.Bl -tag -width indent
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.It Fl b , -background
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Background immediately.
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This is useful for startup scripts which don't disable link messages for
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carrier status.
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.It Fl c , -script Ar script
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Use this
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.Ar script
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instead of the default
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.Pa @SCRIPT@ .
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.It Fl d , -debug
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Echo debug and informational messages to the console.
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Subsequent debug options stop
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.Nm
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from daemonising.
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.It Fl f , -config Ar file
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Specify a config to load instead of
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.Pa @SYSCONFDIR@/dhcpcd.conf .
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.Nm
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always processes the config file before any command line options.
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.It Fl h , -hostname Ar hostname
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By default,
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.Nm
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sends the current hostname to the DHCP server so it can register in DNS.
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You can use this option to specify the
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.Ar hostname
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sent, or an empty string to
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stop any
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.Ar hostname
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from being sent.
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.It Fl i , -vendorclassid Ar vendorclassid
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Override the
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.Ar vendorclassid
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field sent. The default is
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dhcpcd <version>.
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If not set then none is sent.
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.It Fl k , -release
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This causes an existing
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.Nm
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process running on the
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.Ar interface
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to release its lease, deconfigure the
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.Ar interface
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and then exit.
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.Nm
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then waits until this process has exited.
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.It Fl l , -leasetime Ar seconds
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Request a specific lease time in
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.Ar seconds .
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By default
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.Nm
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does not request any lease time and leaves the it in the hands of the
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DHCP server.
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.It Fl m , -metric Ar metric
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Added routes will use the
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.Ar metric
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on systems where this is supported
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.Po
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presently only Linux
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.Pc .
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Route metrics allow the addition of routes to the same destination across
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different interfaces, the lower the metric the more it is preferred.
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.It Fl o , -option Ar option
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Request the DHCP
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.Ar option
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variable for use in
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.Pa @SCRIPT@ .
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.It Fl n , -rebind
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Notifies an existing
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.Nm
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process running on the
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.Ar interface
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to rebind it's lease.
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.Nm
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will not re-configure itself or use any other command line arguments.
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.Nm
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will timeout the rebind after 30 seconds at which point the lease will be
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expired and
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.Nm
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will enter the discovery state to obtain a new lease.
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Use the
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.Fl t , -timeout
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option to change this.
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If
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.Nm
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is not running, then it starts up as normal.
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This option used to be renew, but rebind is more accurate as we need to
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broadcast the request instead of unicasting.
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.It Fl p , -persistent
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.Nm
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normally deconfigures the
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.Ar interface
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and configuration when it exits.
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Sometimes, this isn't desirable if for example you have root mounted over NFS.
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You can use this option to stop this from happening.
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.It Fl r , -request Op Ar address
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.Nm
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normally sends a DHCP DISCOVER to find servers to offer an address.
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.Nm
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then requests the address used.
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You can use this option to skip the BROADCAST step and just request the
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.Ar address .
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The downside is if you request an
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.Ar address
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the DHCP server does not know about or the DHCP server is not
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authorative, it will remain silent.
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In this situation, we go back to the init state and DISCOVER again.
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If no
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.Ar address
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is given then the first address currently assigned to the
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.Ar interface
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is used.
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.It Fl s , -inform Op Ar address Ns Op Ar /cidr
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Behaves like
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.Fl r , -request
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as above, but sends a DHCP INFORM instead of a REQUEST.
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This does not get a lease as such, just notifies the DHCP server of the
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.Ar address
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in use.
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You should also include the optional
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.Ar cidr
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network number in-case the address is not already configured on the interface.
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.Nm
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remains running and pretends it has an infinite lease.
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.Nm
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will not de-configure the interface when it exits.
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If
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.Nm
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fails to contact a DHCP server then it returns a failure instead of falling
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back on IPv4LL.
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.It Fl t , -timeout Ar seconds
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Timeout after
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.Ar seconds ,
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instead of the default 30.
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A setting of 0
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.Ar seconds
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causes
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.Nm
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to wait forever to get a lease.
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.It Fl u , -userclass Ar class
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Tags the DHCP message with the userclass
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.Ar class .
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DHCP servers use this give members of the class DHCP options other than the
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default, without having to know things like hardware address or hostname.
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.It Fl v , -vendor Ar code , Ns Ar value
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Add an enscapulated vendor option.
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.Ar code
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should be between 1 and 254 inclusive.
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Examples.
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.Pp
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Set the vendor option 01 with an IP address.
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.D1 dhcpcd \-v 01,192.168.0.2 eth0
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Set the vendor option 02 with a hex code.
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.D1 dhcpcd \-v 02,01:02:03:04:05 eth0
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Do the above and set a third option with a string and not an IP address.
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.D1 dhcpcd \-v 01,192.168.0.2 \-v 02,01:02:03:04:05 \-v 03,\e"192.168.0.2\e" eth0
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.It Fl x , -exit
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This will signal an existing
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.Nm
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process running on the
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.Ar interface
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to deconfigure the
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.Ar interface
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and exit.
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.Nm
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then waits until this process has exited.
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.It Fl D , -duid
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Generate an
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.Li RFC 4361
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compliant clientid.
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This requires persistent storage and not all DHCP servers work with it so it's
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not enabled by default.
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.Nm
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generates the DUID and stores in it
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.Pa @SYSCONFDIR@/dhcpcd.duid
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This file should not be copied to other hosts.
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.It Fl E , -lastlease
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If
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.Nm
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cannot obtain a lease, then try to use the last lease acquired for the
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interface.
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If the
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.Fl p, -persistent
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option is not given then the lease is used if it hasn't expired.
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.It Fl F , -fqdn Ar fqdn
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Requests that the DHCP server updates DNS using FQDN instead of just a
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hostname.
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Valid values for
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.Ar fqdn
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are disable, none, ptr and both.
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The current hostname or the hostname specified using the
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.Fl h , -hostname
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option must be a FQDN.
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.Nm
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itself never does any DNS updates.
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.Nm
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encodes the FQDN hostname as specified in
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.Li RFC1035 .
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.It Fl I , -clientid Ar clientid
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Send the
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.Ar clientid .
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If the string is of the format 01:02:03 then it is encoded as hex.
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For interfaces whose hardware address is longer than 8 bytes, or if the
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.Ar clientid
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is an empty string then
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.Nm
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sends a default
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.Ar clientid
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of the hardware family and the hardware address.
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.El
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.Ss Restriciting behaviour
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.Nm
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will try to do as much as it can by default.
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However, there are sometimes situations where you don't want the things to be
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configured exactly how the the DHCP server wants.
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Here are some options that deal with turning these bits off.
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.Bl -tag -width indent
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.It Fl q , -quiet
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Quiet
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.Nm
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on the command line, only warnings and errors will be displayed.
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The messages are still logged though.
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.It Fl A , -noarp
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Don't request or claim the address by ARP.
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This also disables IPv4LL.
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.It Fl B , -nobackground
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Don't run in the background when we acquire a lease.
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This is mainly useful for running under the control of another process, such
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as a debugger or a network manager.
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.It Fl C , -nohook Ar script
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Don't run this hook script.
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Matches full name, or prefixed with 2 numbers optionally ending with
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.Pa .sh .
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.Pp
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So to stop dhcpcd from touching your DNS or MTU settings you would do:-
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.D1 dhcpcd -C resolv.conf -C mtu eth0
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.It Fl G , -nogateway
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Don't set any default routes.
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.It Fl K , -nolink
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Don't receive link messages for carrier status.
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You should only have to use this with buggy device drivers or running
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.Nm
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through a network manager.
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.It Fl L , -noipv4ll
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Don't use IPv4LL (aka APIPA, aka Bonjour, aka ZeroConf).
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.It Fl O , -nooption Ar option
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Don't request the specified option.
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If no option given, then don't request any options other than those to
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configure the interface and routing.
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.It Fl Q , -require Ar option
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Requires the
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.Ar option
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to be present in all DHCP messages, otherwise the message is ignored.
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.It Fl T, -test
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On receipt of OFFER messages just call
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.Pa @SCRIPT@
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with the reason of TEST which echo's the DHCP variables found in the message
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to the console.
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The interface configuration isn't touched and neither are any configuration
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files.
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.It Fl V, -variables
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Display a list of option codes and the associated variable for use in
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.Xr dhcpcd-run-hooks 8 .
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.It Fl X, -blacklist Ar address
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Ignores all DHCP messages which have this
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.Ar address
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as the server ID.
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This may be expanded in future releases to ignore all packets
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matching either the IP or hardware
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.Ar address .
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.El
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.Sh NOTES
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.Nm
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requires a Berkley Packet Filter, or BPF device on BSD based systems and a
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Linux Socket Filter, or LPF device on Linux based systems.
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.Sh FILES
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.Bl -ohang
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.It Pa @SYSCONFDIR@/dhcpcd.conf
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Configuration file for dhcpcd.
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If you always use the same options, put them here.
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.It Pa @SYSCONFDIR@/dhcpcd.duid
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Text file that holds the DUID used to identify the host.
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.It Pa @SCRIPT@
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Bourne shell script that is run to configure or deconfigure an interface.
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.It Pa @HOOKDIR@
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A directory containing bourne shell scripts that are run by the above script.
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Each script can be disabled by using the
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.Fl C , -nohook
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option described above.
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.It Pa @DBDIR@/dhcpcd\- Ns Ar interface Ns .lease
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The actual DHCP message send by the server. We use this when reading the last
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lease and use the files mtime as when it was issued.
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.It Pa /var/run/dhcpcd\- Ns Ar interface Ns .pid
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Stores the PID of
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.Nm
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running on the
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.Ar interface .
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.El
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.Sh SEE ALSO
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.Xr dhcpcd.conf 5 ,
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.Xr dhcpcd-run-hooks 8 ,
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.Xr resolv.conf 5 ,
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.Xr resolvconf 8 ,
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.Sh STANDARDS
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RFC 2131, RFC 2132, RFC 2855, RFC 3004, RFC 3361, RFC 3396, RFC 3397,
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RFC 3442, RFC 3927, RFC 4361, RFC 4390, RFC 4702.
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.Sh AUTHORS
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|
.An Roy Marples <roy@marples.name>
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.Sh BUGS
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Please report them to http://roy.marples.name/projects/dhcpcd
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