dhcpcd.conf.5

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.Dd May 21, 2012
.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 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 .
.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.
This requires persistent storage and not all DHCP servers work with it so it's
not enabled by default.
The duid generated will be held in
.Pa /etc/dhcpcd.duid
and should not be copied to other hosts.
.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 fqdn Op none | ptr | both
none disables FQDN encoding, ptr just asks the DHCP server to update the PTR
record of the host in DNS whereas both also updates the A record.
.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.
.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.
.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 noarp
Don't send any ARP requests.
This also disables IPv4LL.
.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 solicition 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 options separated by commas, spaces or more option lines.
.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 if 0 seconds causes
.Nm dhcpcd
to skip the reboot phase and go straight into discover.
.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 /libexec/dhcpcd-run-hooks .
.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.
.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
Wait for an address to be assigned before forking to the background.
.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 roy@marples.name
.Sh BUGS
Please report them to
.Lk http://roy.marples.name/projects/dhcpcd