.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.\" Copyright (c) 2006-2021 Roy Marples
.\" All rights reserved
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 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.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
.\"
.Dd August 23, 2021
.Dt DHCPCD 8
.Os
.Sh NAME
.Nm dhcpcd
.Nd a DHCP client
.Sh SYNOPSIS
.Nm
.Op Fl 146ABbDdEGgHJKLMNPpqTV
.Op Fl C , Fl Fl nohook Ar hook
.Op Fl c , Fl Fl script Ar script
.Op Fl e , Fl Fl env Ar value
.Op Fl F , Fl Fl fqdn Ar FQDN
.Op Fl f , Fl Fl config Ar file
.Op Fl h , Fl Fl hostname Ar hostname
.Op Fl I , Fl Fl clientid Ar clientid
.Op Fl i , Fl Fl vendorclassid Ar vendorclassid
.Op Fl j , Fl Fl logfile Ar logfile
.Op Fl l , Fl Fl leasetime Ar seconds
.Op Fl m , Fl Fl metric Ar metric
.Op Fl O , Fl Fl nooption Ar option
.Op Fl o , Fl Fl option Ar option
.Op Fl Q , Fl Fl require Ar option
.Op Fl r , Fl Fl request Ar address
.Op Fl S , Fl Fl static Ar value
.Op Fl s , Fl Fl inform Ar address Ns Op Ar /cidr Ns Op Ar /broadcast_address
.Op Fl Fl inform6
.Op Fl t , Fl Fl timeout Ar seconds
.Op Fl u , Fl Fl userclass Ar class
.Op Fl v , Fl Fl vendor Ar code , Ar value
.Op Fl W , Fl Fl whitelist Ar address Ns Op Ar /cidr
.Op Fl w
.Op Fl Fl waitip Ns = Ns Op 4 | 6
.Op Fl y , Fl Fl reboot Ar seconds
.Op Fl X , Fl Fl blacklist Ar address Ns Op Ar /cidr
.Op Fl Z , Fl Fl denyinterfaces Ar pattern
.Op Fl z , Fl Fl allowinterfaces Ar pattern
.Op Fl Fl inactive
.Op Fl Fl configure
.Op Fl Fl noconfigure
.Op interface
.Op ...
.Nm
.Fl n , Fl Fl rebind
.Op interface
.Nm
.Fl k , Fl Fl release
.Op interface
.Nm
.Fl U , Fl Fl dumplease
.Op Ar interface
.Nm
.Fl Fl version
.Nm
.Fl x , Fl Fl exit
.Op interface
.Sh DESCRIPTION
.Nm
is an implementation of the DHCP client specified in
.Li RFC 2131 .
.Nm
gets the host information
.Po
IP address, routes, etc
.Pc
from a DHCP server and configures the network
.Ar interface
of the
machine on which it is running.
.Nm
then runs the configuration script which writes DNS information to
.Xr resolvconf 8 ,
if available, otherwise directly to
.Pa /etc/resolv.conf .
If the hostname is currently blank, (null) or localhost, or
.Va force_hostname
is YES or TRUE or 1 then
.Nm
sets the hostname to the one supplied by the DHCP server.
.Nm
then daemonises and waits for the lease renewal time to lapse.
It will then attempt to renew its lease and reconfigure if the new lease
changes when the lease begins to expire or the DHCP server sends a message
to renew early.
.Pp
If any interface reports a working carrier then
.Nm
will try to obtain a lease before forking to the background,
otherwise it will fork right away.
This behaviour can be modified with the
.Fl b , Fl Fl background
and
.Fl w , Fl Fl waitip
options.
.Pp
.Nm
is also an implementation of the BOOTP client specified in
.Li RFC 951 .
.Pp
.Nm
is also an implementation of the IPv6 Router Solicitor as specified in
.Li RFC 4861
and
.Li RFC 6106 .
.Pp
.Nm
is also an implementation of the IPv6 Privacy Extensions to AutoConf as
specified in
.Li RFC 4941 .
This feature needs to be enabled in the kernel and
.Nm
will start using it.
.Pp
.Nm
is also an implementation of the DHCPv6 client as specified in
.Li RFC 3315 .
By default,
.Nm
only starts DHCPv6 when instructed to do so by an IPV6 Router Advertisement.
If no Identity Association is configured,
then a Non-temporary Address is requested.
.Ss Local Link configuration
If
.Nm
failed to obtain a lease, it probes for a valid IPv4LL address
.Po
aka ZeroConf, aka APIPA
.Pc .
Once obtained it restarts the process of looking for a DHCP server to get a
proper address.
.Pp
When using IPv4LL,
.Nm
nearly always succeeds and returns an exit code of 0.
In the rare case it fails, it normally means that there is a reverse ARP proxy
installed which always defeats IPv4LL probing.
To disable this behaviour, you can use the
.Fl L , Fl Fl noipv4ll
option.
.Ss Multiple interfaces
If a list of interfaces are given on the command line, then
.Nm
only works with those interfaces, otherwise
.Nm
discovers available Ethernet interfaces that can be configured.
When
.Nm
not limited to one interface on the command line,
it is running in Manager mode.
The
.Nm dhcpcd-ui
project expects dhcpcd to be running this way.
.Pp
If a single interface is given then
.Nm
only works for that interface and runs as a separate instance to other
.Nm
processes.
.Fl w , Fl Fl waitip
option is enabled in this instance to maintain compatibility with older
versions.
Using a single interface also affects the
.Fl k ,
.Fl N ,
.Fl n
and
.Fl x
options, where the same interface will need to be specified, as a lack of an
interface will imply Manager mode which this is not.
To force starting in Manager mode with only one interface, the
.Fl M , Fl Fl manager
option can be used.
.Pp
Interfaces are preferred by carrier, DHCP lease/IPv4LL and then lowest metric.
For systems that support route metrics, each route will be tagged with the
metric, otherwise
.Nm
changes the routes to use the interface with the same route and the lowest
metric.
See options below for controlling which interfaces we allow and deny through
the use of patterns.
.Pp
Non-ethernet interfaces and some virtual ethernet interfaces
such as TAP and bridge are ignored by default,
as is the FireWire interface.
To work with these devices they either need to be specified on the command line,
be listed in
.Fl Fl allowinterfaces
or have an interface directive in
.Pa /etc/dhcpcd.conf .
.Ss Hooking into events
.Nm
runs
.Pa /usr/lib/dhcpcd/dhcpcd-run-hooks ,
or the script specified by the
.Fl c , Fl Fl script
option.
This script runs each script found in
.Pa /usr/lib/dhcpcd/dhcpcd-hooks
in a lexical order.
The default installation supplies the scripts
.Pa 01-test ,
.Pa 02-dump ,
.Pa 20-resolv.conf
and
.Pa 30-hostname .
You can disable each script by using the
.Fl C , Fl Fl nohook
option.
See
.Xr dhcpcd-run-hooks 8
for details on how these scripts work.
.Nm
currently ignores the exit code of the script.
.Pp
More scripts are supplied in
.Pa /usr/share/dhcpcd/hooks
and need to be copied to
.Pa /usr/lib/dhcpcd/dhcpcd-hooks
if you intend to use them.
For example, you could install
.Pa 29-lookup-hostname
so that
.Nm
can lookup the hostname of the IP address in DNS if no hostname
is given by the lease and one is not already set.
.Ss Fine tuning
You can fine-tune the behaviour of
.Nm
with the following options:
.Bl -tag -width indent
.It Fl b , Fl Fl background
Background immediately.
This is useful for startup scripts which don't disable link messages for
carrier status.
.It Fl c , Fl Fl script Ar script
Use this
.Ar script
instead of the default
.Pa /usr/lib/dhcpcd/dhcpcd-run-hooks .
.It Fl D , Fl Fl duid Op Ar ll | lt | uuid | value
Use a DHCP Unique Identifier.
If a system UUID is available, that will be used to create a DUID-UUID,
otherwise if persistent storage is available then a DUID-LLT
(link local address + time) is generated,
otherwise DUID-LL is generated (link local address).
The DUID type can be hinted as an optional parameter if the file
.Pa /var/lib/dhcpcd/duid
does not exist.
If not
.Va ll ,
.Va lt
or
.Va uuid
then
.Va value
will be converted from 00:11:22:33 format.
This, plus the IAID will be used as the
.Fl I , Fl Fl clientid .
The DUID generated will be held in
.Pa /var/lib/dhcpcd/duid
and should not be copied to other hosts.
This file also takes precedence over the above rules except for setting a value.
.It Fl d , Fl Fl debug
Echo debug messages to the stderr and syslog.
.It Fl E , Fl Fl lastlease
If
.Nm
cannot obtain a lease, then try to use the last lease acquired for the
interface.
.It Fl Fl lastleaseextend
Same as the above, but the lease will be retained even if it expires.
.Nm
will give it up if any other host tries to claim it for their own via ARP.
This violates RFC 2131, section 3.7, which states the lease should be
dropped once it has expired.
.It Fl e , Fl Fl env Ar value
Push
.Ar value
to the environment for use in
.Xr dhcpcd-run-hooks 8 .
For example, you can force the hostname hook to always set the hostname with
.Fl e
.Va force_hostname=YES .
.It Fl g , Fl Fl reconfigure
.Nm
will re-apply IP address, routing and run
.Xr dhcpcd-run-hooks 8
for each interface.
This is useful so that a 3rd party such as PPP or VPN can change the routing
table and / or DNS, etc and then instruct
.Nm
to put things back afterwards.
.Nm
does not read a new configuration when this happens - you should rebind if you
need that functionality.
.It Fl F , Fl Fl fqdn Ar fqdn
Requests that the DHCP server updates DNS using FQDN instead of just a
hostname.
Valid values for
.Ar fqdn
are disable, none, ptr and both.
.Nm
itself never does any DNS updates.
.Nm
encodes the FQDN hostname as specified in
.Li RFC 1035 .
.It Fl f , Fl Fl config Ar file
Specify a config to load instead of
.Pa /etc/dhcpcd.conf .
.Nm
always processes the config file before any command line options.
.It Fl h , Fl Fl hostname Ar hostname
Sends
.Ar hostname
to the DHCP server so it can be registered in DNS.
If
.Ar hostname
is an empty string then the current system hostname is sent.
If
.Ar hostname
is a FQDN (i.e., contains a .) then it will be encoded as such.
.It Fl I , Fl Fl clientid Ar clientid
Send the
.Ar clientid .
If the string is of the format 01:02:03 then it is encoded as hex.
For interfaces whose hardware address is longer than 8 bytes, or if the
.Ar clientid
is an empty string then
.Nm
sends a default
.Ar clientid
of the hardware family and the hardware address.
.It Fl i , Fl Fl vendorclassid Ar vendorclassid
Override the DHCPv4
.Ar vendorclassid
field sent.
The default is
dhcpcd-<version>:<os>:<machine>:<platform>.
For example
.D1 dhcpcd-5.5.6:NetBSD-6.99.5:i386:i386
If not set then none is sent.
Some badly configured DHCP servers reject unknown vendorclassids.
To work around it, try and impersonate Windows by using the MSFT vendorclassid.
.It Fl j , Fl Fl logfile Ar logfile
Writes to the specified
.Ar logfile .
.Nm
still writes to
.Xr syslog 3 .
The
.Ar logfile
is reopened when
.Nm
receives the
.Dv SIGUSR2
signal.
.It Fl k , Fl Fl release Op Ar interface
This causes an existing
.Nm
process running on the
.Ar interface
to release its lease and de-configure the
.Ar interface
regardless of the
.Fl p , Fl Fl persistent
option.
If no
.Ar interface
is specified then this applies to all interfaces in Manager mode.
If no interfaces are left running,
.Nm
will exit.
.It Fl l , Fl Fl leasetime Ar seconds
Request a lease time of
.Ar seconds .
.Ar -1
represents an infinite lease time.
By default
.Nm
does not request any lease time and leaves it in the hands of the
DHCP server.
.It Fl M , Fl Fl manager
Start
.Nm
in Manager mode even if only one interface specified on the command line.
See the Multiple Interfaces section above.
.It Fl m , Fl Fl metric Ar metric
Metrics are used to prefer an interface over another one, lowest wins.
.Nm
will supply a default metric of 1000 +
.Xr if_nametoindex 3 .
This will be offset by 2000 for wireless interfaces, with additional offsets
of 1000000 for IPv4LL and 2000000 for roaming interfaces.
.It Fl n , Fl Fl rebind Op Ar interface
Notifies
.Nm
to reload its configuration and rebind the specified
.Ar interface .
If no
.Ar interface
is specified then this applies to all interfaces in Manager mode.
If
.Nm
is not running, then it starts up as normal.
.It Fl N , Fl Fl renew Op Ar interface
Notifies
.Nm
to renew existing addresses on the specified
.Ar interface .
If no
.Ar interface
is specified then this applies to all interfaces in Manager mode.
If
.Nm
is not running, then it starts up as normal.
Unlike the
.Fl n , Fl Fl rebind
option above, the configuration for
.Nm
is not reloaded.
.It Fl o , Fl Fl option Ar option
Request the DHCP
.Ar option
variable for use in
.Pa /usr/lib/dhcpcd/dhcpcd-run-hooks .
.It Fl p , Fl Fl persistent
.Nm
normally de-configures the
.Ar interface
and configuration when it exits.
Sometimes, this isn't desirable if, for example, you have root mounted over
NFS or SSH clients connect to this host and they need to be notified of
the host shutting down.
You can use this option to stop this from happening.
.It Fl r , Fl Fl request Ar address
Request the
.Ar address
in the DHCP DISCOVER message.
There is no guarantee this is the address the DHCP server will actually give.
If no
.Ar address
is given then the first address currently assigned to the
.Ar interface
is used.
.It Fl s , Fl Fl inform Ar address Ns Op Ar /cidr Ns Op Ar /broadcast_address
Behaves like
.Fl r , Fl Fl request
as above, but sends a DHCP INFORM instead of DISCOVER/REQUEST.
This does not get a lease as such, just notifies the DHCP server of the
.Ar address
in use.
You should also include the optional
.Ar cidr
network number in case the address is not already configured on the interface.
.Nm
remains running and pretends it has an infinite lease.
.Nm
will not de-configure the interface when it exits.
If
.Nm
fails to contact a DHCP server then it returns a failure instead of falling
back on IPv4LL.
.It Fl Fl inform6
Performs a DHCPv6 Information Request.
No address is requested or specified, but all other DHCPv6 options are allowed.
This is normally performed automatically when the IPv6 Router Advertises
that the client should perform this operation.
This option is only needed when
.Nm
is not processing IPv6RA messages and the need for DHCPv6 Information Request
exists.
.It Fl S , Fl Fl static Ar value
Configures a static DHCP
.Ar value .
If you set
.Ic ip_address
then
.Nm
will not attempt to obtain a lease and just use the value for the address with
an infinite lease time.
.Pp
Here is an example which configures a static address, routes and DNS.
.D1 dhcpcd -S ip_address=192.168.0.10/24 \e
.D1 -S routers=192.168.0.1 \e
.D1 -S domain_name_servers=192.168.0.1 \e
.D1 eth0
.Pp
You cannot presently set static DHCPv6 values.
Use the
.Fl e , Fl Fl env
option instead.
.It Fl t , Fl Fl timeout Ar seconds
Timeout after
.Ar seconds ,
instead of the default 30.
A setting of 0
.Ar seconds
causes
.Nm
to wait forever to get a lease.
If
.Nm
is working on a single interface then
.Nm
will exit when a timeout occurs, otherwise
.Nm
will fork into the background.
.It Fl u , Fl Fl userclass Ar class
Tags the DHCPv4 message with the userclass
.Ar class .
DHCP servers use this to give members of the class DHCP options other than the
default, without having to know things like hardware address or hostname.
.It Fl v , Fl Fl vendor Ar code , Ns Ar value
Add an encapsulated vendor option.
.Ar code
should be between 1 and 254 inclusive.
To add a raw vendor string, omit
.Ar code
but keep the comma.
Examples.
.Pp
Set the vendor option 01 with an IP address.
.D1 dhcpcd \-v 01,192.168.0.2 eth0
Set the vendor option 02 with a hex code.
.D1 dhcpcd \-v 02,01:02:03:04:05 eth0
Set the vendor option 03 with an IP address as a string.
.D1 dhcpcd \-v 03,\e"192.168.0.2\e" eth0
Set un-encapsulated vendor option to hello world.
.D1 dhcpcd \-v ,"hello world" eth0
.It Fl Fl version
Display both program version and copyright information.
.Nm
then exits before doing any configuration.
.It Fl w
Wait for an address to be assigned before forking to the background.
Does not take an argument, unlike the below option.
.It Fl Fl waitip Ns = Ns Op 4 | 6
Wait for an address to be assigned before forking to the background.
4 means wait for an IPv4 address to be assigned.
6 means wait for an IPv6 address to be assigned.
If no argument is given,
.Nm
will wait for any address protocol to be assigned.
It is possible to wait for more than one address protocol and
.Nm
will only fork to the background when all waiting conditions are satisfied.
.It Fl x , Fl Fl exit Op Ar interface
This will signal an existing
.Nm
process running on the
.Ar interface
to exit.
If no
.Ar interface
is specified, then the above is applied to all interfaces in Manager mode.
See the
.Fl p , Fl Fl persistent
option to control configuration persistence on exit,
which is enabled by default in
.Xr dhcpcd.conf 5 .
.Nm
then waits until this process has exited.
.It Fl y , Fl Fl reboot Ar seconds
Allow
.Ar reboot
seconds before moving to the discover phase if we have an old lease to use.
Allow
.Ar reboot
seconds before starting fallback states from the discover phase.
IPv4LL is started when the first
.Ar reboot
timeout is reached.
The default is 5 seconds.
A setting of 0 seconds causes
.Nm
to skip the reboot phase and go straight into discover.
This has no effect on DHCPv6 other than skipping the reboot phase.
.El
.Ss Restricting behaviour
.Nm
will try to do as much as it can by default.
However, there are sometimes situations where you don't want the things to be
configured exactly how the DHCP server wants.
Here are some options that deal with turning these bits off.
.Pp
Note that when
.Nm
is restricted to a single interface then the interface also needs to be
specified when asking
.Nm
to exit using the commandline.
If the protocol is restricted as well then the protocol needs to be included
with the exit instruction.
.Bl -tag -width indent
.It Fl 1 , Fl Fl oneshot
Exit after configuring an interface.
Use the
.Fl w , Fl Fl waitip
option to specify which protocol(s) to configure before exiting.
.It Fl 4 , Fl Fl ipv4only
Configure IPv4 only.
.It Fl 6 , Fl Fl ipv6only
Configure IPv6 only.
.It Fl A , Fl Fl noarp
Don't request or claim the address by ARP.
This also disables IPv4LL.
.It Fl B , Fl Fl nobackground
Don't run in the background when we acquire a lease.
This is mainly useful for running under the control of another process, such
as a debugger or a network manager.
.It Fl C , Fl Fl nohook Ar script
Don't run this hook script.
Matches full name, or prefixed with 2 numbers optionally ending with
.Pa .sh .
.Pp
So to stop
.Nm
from touching your DNS settings you would do:-
.D1 dhcpcd -C resolv.conf eth0
.It Fl G , Fl Fl nogateway
Don't set any default routes.
.It Fl H , Fl Fl xidhwaddr
Use the last four bytes of the hardware address as the DHCP xid instead
of a randomly generated number.
.It Fl J , Fl Fl broadcast
Instructs the DHCP server to broadcast replies back to the client.
Normally this is only set for non-Ethernet interfaces,
such as FireWire and InfiniBand.
In most instances,
.Nm
will set this automatically.
.It Fl K , Fl Fl nolink
Don't receive link messages for carrier status.
You should only have to use this with buggy device drivers or running
.Nm
through a network manager.
.It Fl L , Fl Fl noipv4ll
Don't use IPv4LL (aka APIPA, aka Bonjour, aka ZeroConf).
.It Fl O , Fl Fl nooption Ar option
Removes the
.Ar option
from the DHCP message before processing.
.It Fl P , Fl Fl printpidfile
Print the
.Pa pidfile
.Nm
will use based on command-line arguments to stdout.
.It Fl Q , Fl Fl require Ar option
Requires the
.Ar option
to be present in all DHCP messages, otherwise the message is ignored.
To enforce that
.Nm
only responds to DHCP servers and not BOOTP servers, you can
.Fl Q
.Ar dhcp_message_type .
.It Fl q , Fl Fl quiet
Quiet
.Nm
on the command line, only warnings and errors will be displayed.
If this option is used another time then all console output is disabled.
These messages are still logged via
.Xr syslog 3 .
.It Fl T , Fl Fl test
On receipt of DHCP messages just call
.Pa /usr/lib/dhcpcd/dhcpcd-run-hooks
with the reason of TEST which echos the DHCP variables found in the message
to the console.
The interface configuration isn't touched and neither are any configuration
files.
The
.Ar rapid_commit
option is not sent in TEST mode so that the server does not lease an address.
To test INFORM the interface needs to be configured with the desired address
before starting
.Nm .
.It Fl U , Fl Fl dumplease Op Ar interface
Dumps the current lease for the
.Ar interface
to stdout.
If no
.Ar interface
is given then all interfaces are dumped.
Use the
.Fl 4
or
.Fl 6
flags to specify an address family.
If a lease is piped in via standard input then that is dumped.
In this case, specifying an address family is mandatory.
.It Fl V , Fl Fl variables
Display a list of option codes, the associated variable and encoding for use in
.Xr dhcpcd-run-hooks 8 .
Variables are prefixed with new_ and old_ unless the option number is -.
Variables without an option are part of the DHCP message and cannot be
directly requested.
.It Fl W , Fl Fl whitelist Ar address Ns Op /cidr
Only accept packets from
.Ar address Ns Op /cidr .
.Fl X , Fl Fl blacklist
is ignored if
.Fl W , Fl Fl whitelist
is set.
.It Fl X , Fl Fl blacklist Ar address Ns Op Ar /cidr
Ignore all packets from
.Ar address Ns Op Ar /cidr .
.It Fl Z , Fl Fl denyinterfaces Ar pattern
When discovering interfaces, the interface name must not match
.Ar pattern
which is a space or comma separated list of patterns passed to
.Xr fnmatch 3 .
.It Fl z , Fl Fl allowinterfaces Ar pattern
When discovering interfaces, the interface name must match
.Ar pattern
which is a space or comma separated list of patterns passed to
.Xr fnmatch 3 .
If the same interface is matched in
.Fl Z , Fl Fl denyinterfaces
then it is still denied.
.It Fl Fl inactive
Don't start any interfaces other than those specified on the command line.
This allows
.Nm
to be started in Manager mode and then wait for subsequent
.Nm
commands to start each interface as required.
.It Fl Fl configure
Allows
.Nm
to configure the system.
This is the default behaviour and sets
.Ev if_configured=true .
.It Fl Fl noconfigure
.Nm
will not configure the system at all.
This is only of use if the
.Fl Fl script
that
.Nm
calls at each network event configures the system instead.
This is different from
.Fl T , Fl Fl test
mode in that it's not one shot and the only change to the environment is the
addition of
.Ev if_configured=false .
.It Fl Fl nodev
Don't load any
.Pa /dev
management modules.
.El
.Sh 3RDPARTY LINK MANAGEMENT
Some interfaces require configuration by 3rd parties, such as PPP or VPN.
When an interface configuration in
.Nm
is marked as STATIC or INFORM without an address then
.Nm
will monitor the interface until an address is added or removed from it and
act accordingly.
For point to point interfaces (like PPP), a default route to its
destination is automatically added to the configuration.
If the point to point interface is configured for INFORM, then
.Nm
unicasts INFORM to the destination, otherwise it defaults to STATIC.
.Sh NOTES
.Nm
requires a Berkley Packet Filter, or BPF device on BSD based systems and a
Linux Socket Filter, or LPF device on Linux based systems for all IPv4
configuration.
.Pp
If restricting
.Nm
to a single interface and optionally address family via the command-line
then all further calls to
.Nm
to rebind, reconfigure or exit need to include the same restrictive flags
so that
.Nm
knows which process to signal.
.Pp
Some DHCP servers implement ClientID filtering.
If
.Nm
is replacing an in-use DHCP client then you might need to adjust the clientid
option
.Nm
sends to match.
If using a DUID in place of the ClientID, edit
.Pa /var/lib/dhcpcd/duid
accordingly.
.Sh FILES
.Bl -ohang
.It Pa /etc/dhcpcd.conf
Configuration file for dhcpcd.
If you always use the same options, put them here.
.It Pa /usr/lib/dhcpcd/dhcpcd-run-hooks
Bourne shell script that is run to configure or de-configure an interface.
.It Pa /usr/lib/x86_64-linux-gnu/dhcpcd/dev
Linux
.Pa /dev
management modules.
.It Pa /usr/lib/dhcpcd/dhcpcd-hooks
A directory containing bourne shell scripts that are run by the above script.
Each script can be disabled by using the
.Fl C , Fl Fl nohook
option described above.
.It Pa /var/lib/dhcpcd/duid
Text file that holds the DUID used to identify the host.
.It Pa /var/lib/dhcpcd/secret
Text file that holds a secret key known only to the host.
.It Pa /var/lib/dhcpcd/ Ns Ar interface Ns Ar -ssid Ns .lease
The actual DHCP message sent by the server.
We use this when reading the last
lease and use the file's mtime as when it was issued.
.It Pa /var/lib/dhcpcd/ Ns Ar interface Ns Ar -ssid Ns .lease6
The actual DHCPv6 message sent by the server.
We use this when reading the last
lease and use the file's mtime as when it was issued.
.It Pa /var/lib/dhcpcd/rdm_monotonic
Stores the monotonic counter used in the
.Ar replay
field in Authentication Options.
.It Pa /run/pid
Stores the PID of
.Nm
running on all interfaces.
.It Pa /run/ Ns Ar interface Ns .pid
Stores the PID of
.Nm
running on the
.Ar interface .
.It Pa /run/sock
Control socket to the manager daemon.
.It Pa /run/unpriv.sock
Unprivileged socket to the manager daemon, only allows state retrieval.
.It Pa /run/ Ns Ar interface Ns .sock
Control socket to per interface daemon.
.It Pa /run/ Ns Ar interface Ns .unpriv.sock
Unprivileged socket to per interface daemon, only allows state retrieval.
.El
.Sh SEE ALSO
.Xr fnmatch 3 ,
.Xr if_nametoindex 3 ,
.Xr dhcpcd.conf 5 ,
.Xr resolv.conf 5 ,
.Xr dhcpcd-run-hooks 8 ,
.Xr resolvconf 8
.Sh STANDARDS
RFC\ 951, RFC\ 1534, RFC\ 2104, RFC\ 2131, RFC\ 2132, RFC\ 2563, RFC\ 2855,
RFC\ 3004, RFC\ 3118, RFC\ 3203, RFC\ 3315, RFC\ 3361, RFC\ 3633, RFC\ 3396,
RFC\ 3397, RFC\ 3442, RFC\ 3495, RFC\ 3925, RFC\ 3927, RFC\ 4039, RFC\ 4075,
RFC\ 4242, RFC\ 4361, RFC\ 4390, RFC\ 4702, RFC\ 4074, RFC\ 4861, RFC\ 4833,
RFC\ 4941, RFC\ 5227, RFC\ 5942, RFC\ 5969, RFC\ 6106, RFC\ 6334, RFC\ 6355,
RFC\ 6603, RFC\ 6704, RFC\ 7217, RFC\ 7550, RFC\ 7844.
.Sh AUTHORS
.An Roy Marples Aq Mt roy@marples.name
.Sh BUGS
Please report them to
.Lk http://roy.marples.name/projects/dhcpcd