dhcpcd configuration file
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
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.
Blank lines and lines starting with # are ignored.
Here's a list of available options:
- When discovering interfaces, the interface name must match
pattern which is a space or comma
separated list of patterns passed to
fnmatch(3). If the same interface is matched
denyinterfaces then it is still
- When discovering interfaces, the interface name must not match
pattern which is a space or comma
separated list of patterns passed to
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.
- Background immediately. This is useful for startup scripts which don't
disable link messages for carrier status.
- Ignores all packets from
- Only accept packets from
blacklist is ignored if
whitelist is set.
- 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,
will set this automatically.
- Push value to the environment for use in
dhcpcd-run-hooks(8). For example, you can
force the hostname hook to always set the hostname with
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,
dhcpcd will still try and set a FQDN
from the hostname and domain options for consistency. To override this,
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
- Send the 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
clientid is an empty string then
dhcpcd sends a default
clientid of the hardware family and the
- Generate an RFC
4361. 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 /etc/dhcpcd.duid and should not
be copied to other hosts.
- Fallback to using this profile if DHCP fails. This allows you to configure
a static profile instead of using ZeroConf.
- Sends hostname to the DHCP server so it
can be registered in DNS. If hostname is
an empty string then the current system hostname is sent. If
hostname is a FQDN (ie, contains a .)
then it will be encoded as such.
- 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.
Also, see the
env option above to control
how the hostname is set on the host.
- Request a DHCPv6 Normal Address for iaid.
If none is specified, a default iaid is
used. If the interface name is 4 characters or less then that is used,
otherwise the interface index is used.
- Request a DHCPv6 Temporary Address for
- Request a DHCPv6 Delegated Prefix for
iaid. If no
interface is given then we will assign a
prefix to every other interface with a unique
sla_id for each, starting from 0.
Otherwise addresses are only assigned for each
sla_id A default
prefix_len of 64 is assumed.
sla_id is an integer and is added to the
prefix which must fit inside prefix_len
less the length of the delegated prefix. You can specify multiple
ia_pd, space separated. IPv6RS should
be disabled globally when requesting a Prefix Delegation like so:
ia_pd 1 eth1/0 eth2/1
- Only configure IPv4.
- Only confgiure IPv6.
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.
itself never does any DNS updates.
dhcpcd encodes the FQDN hostname as
- Subsequent options are only parsed for this
- By default, when
dhcpcd receives an
dhcpcd will only fork to the
background if the RA contains at least one unexpired RDNSS option. Set
this option so to make
fork on an RA.
- 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.
- 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.
- 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.
- Request a leasetime of seconds.
- Metrics are used to prefer an interface over another one, lowest wins.
dhcpcd will supply a default metric of
200 + if_nametoindex(3). An extra 100 will be
added for wireless interfaces.
- IPv4 addresses added will overwrite a pre-existing address instead of
- Don't send any ARP requests. This also disables IPv4LL.
- Don't install any default routes.
- Don't run this hook script. Matches full name, or prefixed with 2 numbers
optionally ending with .sh.
So to stop
dhcpcd from touching your DNS
or MTU settings you would do:-
nohook resolv.conf, mtu
- Don't attempt to obtain an IPv4LL address if we failed to get one via
DHCP. See RFC
- Disable solicitation and receipt of IPv6 Router Advertisements.
- Don't receive link messages about carrier status. You should only set this
for buggy interface drivers.
- Requests the option from the server. It
can be a variable to be used in
dhcpcd-run-hooks(8) or the numerical value.
You can specify more options separated by
commas, spaces or more
Prepend dhcp6_ to option to request a
DHCPv6 option. DHCPv4 options are mapped to DHCPv6 where applicable.
- 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
dhcpcd.conf 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.
- Subsequent options are only parsed for this profile
- Suppress any dhcpcd output to the console, except for errors.
- Allow 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
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
dhcpcd will timeout before moving back
to the DISCOVER phase.
dhcpcd will release the lease prior to
stopping the interface.
- Requires the option to be present in all
DHCP messages, otherwise the message is ignored. It can be a variable to
be used in dhcpcd-run-hooks(8) or the
numerical value. You can specify more options separated by commas, spaces
or more require lines. To enforce that
dhcpcd only responds to DHCP servers
and not BOOTP servers, you can
- Use script instead of the default
- Subsequent options are only parsed for this wireless
- Configures a static value. If you set
dhcpcd will not attempt to obtain a
lease and just use the value for the address with an infinite lease time.
Here is an example which configures a static address, routes and dns.
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.
- 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
dhcpcd to wait forever to get a
- Tag the DHCP messages with the userclass. You can specify more than
- Add an encapsulated vendor option. code
should be between 1 and 254 inclusive. To add a raw vendor string, omit
code but keep the comma. Examples.
Set the vendor option 01 with an IP address.
Set the vendor option 02 with a hex code.
Set the vendor option 03 with an IP address as a string.
Set un-encapsulated vendor option to hello world.
vendor ,"hello world"
- The default is
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.
- Wait for an address to be assigned before forking to the background.
- Use the last four bytes of the hardware address as the DHCP xid instead of
a randomly generated number.
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