dhcpcd/dhcpcd.conf.5.in

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.Dd September 12, 2013
.Dt DHCPCD.CONF 5 SMM
.Os
.Sh NAME
.Nm dhcpcd.conf
.Nd dhcpcd configuration file
.Sh DESCRIPTION
Although
.Nm dhcpcd
can do everything from the command line, there are cases where it's just easier
to do it once in a configuration file.
Most of the options found in
.Xr dhcpcd 8
can be used here.
The first word on the line is the option and the rest of the line is the value.
Leading and trailing whitespace for the option and value are trimmed.
You can escape characters in the value using the \\ character.
.Pp
Blank lines and lines starting with # are ignored.
.Pp
Here's a list of available options:
.Bl -tag -width indent
.It Ic 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
.Ic denyinterfaces
then it is still denied.
.It Ic 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 Ic arping Ar address Op address
.Nm dhcpcd
will arping each address in order before attempting DHCP.
If an address is found, we will select the replying hardware address as the
profile, otherwise the ip address.
Example:
.Pp
.D1 interface bge0
.D1 arping 192.168.0.1
.Pp
.D1 profile 192.168.0.1
.D1 static ip_address=192.168.0.10/24
.It Ic background
Background immediately.
This is useful for startup scripts which don't disable link messages for
carrier status.
.It Ic blacklist Ar address Ns Op /cidr
Ignores all packets from
.Ar address Ns Op /cidr .
.It Ic whitelist Ar address Ns Op /cidr
Only accept packets from
.Ar address Ns Op /cidr .
.Ic blacklist
is ignored if
.Ic whitelist
is set.
.It Ic 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 cases,
.Nm dhcpcd
will set this automatically.
.It Ic dev Ar value
Load the
.Ar value
.Pa /dev
management module.
.Nm dhcpcd
will load the first one found to work, if any.
.It Ic 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
.Ic env
.Va force_hostname=YES .
.Pp
If the hostname is set, will be will set to the FQDN if possible as per
RFC 4702 section 3.1.
If the FQDN option is missing,
.Nm dhcpcd
will still try and set a FQDN from the hostname and domain options for
consistency.
To override this, set
.Ic env
.Va hostname_fqdn=[YES|NO|SERVER] .
A value of server means just what the server says, don't manipulate it.
This could lead to an inconsistent hostname on a DHCPv4 and DHCPv6 network
where the DHCPv4 hostname is short and the DHCPv6 has an FQDN.
DHCPv6 has no hostname option.
.It Ic clientid Ar string
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 dhcpcd
sends a default
.Ar clientid
of the hardware family and the hardware address.
.It Ic duid
Generate an
.Rs
.%T "RFC 4361"
.Re
compliant clientid.
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-LLT generated will be held in
.Pa @SYSCONFDIR@/dhcpcd.duid
and should not be copied to other hosts.
.It Ic persistent
.Nm dhcpcd
normally de-configures the 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 Ic fallback Ar profile
Fallback to using this profile if DHCP fails.
This allows you to configure a static profile instead of using ZeroConf.
.It Ic hostname Ar name
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 (ie, contains a .) then it will be encoded as such.
.It Ic hostname_short
Sends the short hostname to the DHCP server instead of the FQDN.
This is useful because DHCP servers will not register the FQDN in their
DNS if the domain part does not match theirs.
.Pp
Also, see the
.Ic env
option above to control how the hostname is set on the host.
.It Ic ia_na Op Ar iaid
Request a DHCPv6 Normal Address for
.Ar iaid .
If none is specified, a default
.Ar iaid
is used.
If the interface name is 4 characters or less then that is used,
otherwise the interface index is used.
You can request more than one ia_na by specifying a unique iaid for each one.
.It Ic ia_ta Op Ar iaid
Request a DHCPv6 Temporary Address for
.Ar iaid .
You can request more than one ia_ta by specifying a unique iaid for each one.
.It Ic ia_pd Op Ar iaid Op Ar interface Op / Ar sla_id Op / Ar prefix_len
Request a DHCPv6 Delegated Prefix for
.Ar iaid .
If no
.Ar interface
is given then we will assign a prefix to every other interface with a unique
.Ar sla_id
for each, starting from 0.
Otherwise addresses are only assigned for each
.Ar interface
and
.Ar sla_id
A default
.Ar prefix_len
of 64 is assumed.
.Ar sla_id
is an integer and is added to the prefix which must fit inside
.Ar prefix_len
less the length of the delegated prefix.
You can specify multiple
.Ar interface /
.Ar sla_id /
.Ar prefix_len
per
.Ic ia_pd ,
space separated.
IPv6RS should be disabled globally when requesting a Prefix Delegation like so:
.Pp
.D1 noipv6rs
.Pp
.D1 interface eth0
.D1 ia_pd 1 eth1/0 eth2/1
.It Ic ipv4only
Only configure IPv4.
.It Ic ipv6only
Only confgiure IPv6.
.It Ic fqdn Op disable | ptr | both
ptr just asks the DHCP server to update the PTR
record of the host in DNS whereas both also updates the A record.
disable will disable the FQDN option.
The default is both.
.Nm dhcpcd
itself never does any DNS updates.
.Nm dhcpcd
encodes the FQDN hostname as specified in
.Li RFC1035 .
.It Ic interface Ar interface
Subsequent options are only parsed for this
.Ar interface .
.It Ic ipv6ra_fork
By default, when
.Nm dhcpcd
receives an IPv6 RA,
.Nm dhcpcd
will only fork to the background if the RA contains at least one unexpired
RDNSS option.
Set this option so to make
.Nm dhcpcd
always fork on an RA.
.It Ic ipv6ra_own
Disables kernel IPv6 Router Advertisment processing so dhcpcd can manage
addresses and routes.
This does not work reliably on any BSD system, probably due to kernel issues.
.It Ic ipv6ra_own_default
Each time dhcpcd receives an IPv6 Router Adveristment, dhcpcd will manage
the default route only.
This allows dhcpcd to prefer an interface for outbound traffic based on metric
and/or user selection rather than the kernel.
This does work reliably on BSD systems.
.It Ic ipv6rs
Enables IPv6 Router Advertisment solicitation.
This is on by default, but is documented here in the case where it is disabled
globally but needs to be enabled for one interface.
.It Ic leasetime Ar seconds
Request a leasetime of
.Ar seconds .
.It Ic metric Ar metric
Metrics are used to prefer an interface over another one, lowest wins.
.Nm dhcpcd
will supply a default metric of 200 +
.Xr if_nametoindex 3 .
An extra 100 will be added for wireless interfaces.
.It Ic noalias
IPv4 addresses added will overwrite a pre-existing address instead of working
alongside.
.It Ic noarp
Don't send any ARP requests.
This also disables IPv4LL.
.It Ic nodev
Don't load
.Pa /dev
management modules.
.It Ic nogateway
Don't install any default routes.
.It Ic 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 dhcpcd
from touching your DNS or MTU settings you would do:-
.D1 nohook resolv.conf, mtu
.It Ic noipv4ll
Don't attempt to obtain an IPv4LL address if we failed to get one via DHCP.
See
.Rs
.%T "RFC 3927"
.Re
.It Ic noipv6rs
Disable solicitation and receipt of IPv6 Router Advertisements.
.It Ic nolink
Don't receive link messages about carrier status.
You should only set this for buggy interface drivers.
.It Ic option Ar option
Requests the
.Ar option
from the server.
It can be a variable to be used in
.Xr dhcpcd-run-hooks 8
or the numerical value.
You can specify more
.Ar option Ns s
separated by commas, spaces or more
.Ic option
lines.
Prepend dhcp6_ to
.Ar option
to request a DHCPv6 option.
DHCPv4 options are mapped to DHCPv6 where applicable.
.It Ic nooption Ar option
Remove the option from the DHCP message.
This should only be used when a DHCP server sends a non requested option
that should not be processed.
.It Ic destination Ar option
If
.Nm
detects an address added to a point to point interface (PPP, TUN, etc) then
it will set the listed DHCP options to the destination address of the
interface.
.It Ic profile Ar name
Subsequent options are only parsed for this profile
.Ar name .
.It Ic quiet
Suppress any dhcpcd output to the console, except for errors.
.It Ic reboot Ar seconds
Allow
.Ar reboot
seconds before moving to the DISCOVER phase if we have an old lease to use.
The default is 5 seconds.
A setting of 0 seconds causes
.Nm dhcpcd
to skip the REBOOT phase and go straight into DISCOVER.
This is desirable for mobile users because if you change from network A to
network B and they use the same subnet and the address from network A isn't
in use on network B, then the DHCP server will remain silent even if authorative
which means
.Nm dhcpcd
will timeout before moving back to the DISCOVER phase.
.It Ic release
.Nm dhcpcd
will release the lease prior to stopping the interface.
.It Ic require Ar option
Requires the
.Ar option
to be present in all DHCP messages, otherwise the message is ignored.
It can be a variable to be used in
.Xr dhcpcd-run-hooks 8
or the numerical value.
You can specify more options separated by commas, spaces or more require lines.
To enforce that
.Nm dhcpcd
only responds to DHCP servers and not BOOTP servers, you can
.Ic require
.Ar dhcp_message_type .
.It Ic script Ar script
Use
.Ar script
instead of the default
.Pa @SCRIPT@ .
.It Ic ssid Ar ssid
Subsequent options are only parsed for this wireless
.Ar ssid .
.It Ic static Ar value
Configures a static
.Ar value .
If you set
.Ic ip_address
then
.Nm dhcpcd
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 interface eth0
.D1 static ip_address=192.168.0.10/24
.D1 static routers=192.168.0.1
.D1 static domain_name_servers=192.168.0.1
.Pp
Here is an example for PPP which gives the destination a default route.
It uses the special destination keyword to insert the destination address
into the value.
.D1 interface ppp0
.D1 static ip_address=
.D1 destination routers
.It Ic timeout Ar seconds
The default timeout for waiting for a DHCP response is 30 seconds which may
be too long or too short and can be changed here.
A setting of 0
.Ar seconds
causes
.Nm dhcpcd
to wait forever to get a lease.
.It Ic userclass Ar string
Tag the DHCP messages with the userclass.
You can specify more than one.
.It Ic 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 vendor 01,192.168.0.2
Set the vendor option 02 with a hex code.
.D1 vendor 02,01:02:03:04:05
Set the vendor option 03 with an IP address as a string.
.D1 vendor 03,\e"192.168.0.2\e"
Set un-encapsulated vendor option to hello world.
.D1 vendor ,"hello world"
.It Ic vendorclassid Ar string
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 Ic waitip 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 Ic xidhwaddr
Use the last four bytes of the hardware address as the DHCP xid instead
of a randomly generated number.
.El
.Sh SEE ALSO
.Xr dhcpcd-run-hooks 8 ,
.Xr dhcpcd 8 ,
.Xr if_nametoindex 3 ,
.Xr fnmatch 3
.Sh AUTHORS
.An Roy Marples Aq Mt roy@marples.name
.Sh BUGS
Please report them to
.Lk http://roy.marples.name/projects/dhcpcd