DHCPCD.CONF(5) BSD File Formats Manual DHCPCD.CONF(5)NAMEdhcpcd.conf — dhcpcd configuration file
DESCRIPTION
Although 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 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.
Blank lines and lines starting with # are ignored.
Here's a list of available options:
allowinterfaces pattern
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 in
denyinterfaces then it is still denied.
denyinterfaces pattern
When discovering interfaces, the interface name must not match
pattern which is a space or comma separated list of patterns
passed to fnmatch(3).
arping address [address]
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:
interface bge0
arping 192.168.0.1
profile 192.168.0.1
static ip_address=192.168.0.10/24
authprotocol protocol algorithm rdm
Authenticate DHCP messages. See the Supported Protocols section.
authtoken secretid realm expire key
Define a shared key for use in authentication. realm can be to
for use with the delayed prptocol. expire is the date the token
expires and should be formatted "yyy-mm-dd HH:MM". You can use
the keyword forever or 0 which means the token never expires.
background
Background immediately. This is useful for startup scripts which
don't disable link messages for carrier status.
blacklist address[/cidr]
Ignores all packets from address[/cidr].
whitelist address[/cidr]
Only accept packets from address[/cidr]. blacklist is ignored if
whitelist is set.
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, dhcpcd will set
this automatically.
dev value
Load the value /dev management module. dhcpcd will load the
first one found to work, if any.
env value
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 env force_hostname=YES.
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, set env
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.
clientid string
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
hardware address.
duid Generate an RFC 4361. compliant DHCP Unique Identifier. If per‐
sistent storage is available then a DUID-LLT (link local address
+ time) is generated, otherwise DUID-LL is generated (link local
address). This, plus the IAID will be used as the clientid. The
DUID-LLT generated will be held in /etc/dhcpcd.duid and should
not be copied to other hosts.
iaid iaid
Set the Interface Association Identifier to iaid. This option
must be used in an interface block. This defaults to the last 4
bytes of the hardware address assigned to the interface. Each
instance of this should be unique within the scope of the client
and dhcpcd warns if a conflict is detected. If there is a con‐
flict, it is only a problem if the conflicted IAIDs are used on
the same network.
persistent
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.
fallback profile
Fallback to using this profile if DHCP fails. This allows you to
configure a static profile instead of using ZeroConf.
hostname name
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.
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.
Also, see the env option above to control how the hostname is set
on the host.
ia_na [iaid]
Request a DHCPv6 Normal Address for iaid. iaid defaults to the
iaid option as described above. You can request more than one
ia_na by specifying a unique iaid for each one.
ia_ta [iaid]
Request a DHCPv6 Temporary Address for iaid. You can request
more than one ia_ta by specifying a unique iaid for each one.
ia_pd [iaid [interface [/ sla_id [/ prefix_len]]]]
Request a DHCPv6 Delegated Prefix for iaid. This option must be
used in an interface block. 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 interface and sla_id. You cannot assign a pre‐
fix to the requesting interface. dhcpcd has to be running for
all the interfaces it is delegating to. 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 interface / sla_id / prefix_len
per ia_pd, space separated. IPv6RS should be disabled globally
when requesting a Prefix Delegation like so:
noipv6rs
# Don't touch eth3 at all
denyinterfaces eth3
interface eth0
ia_pd 1 eth1/0 eth2/1
# Disable automatic address configuration for eth1
# eth1 still gets a delegated prefix
interface eth1
noipv4
noipv6
ipv4only
Only configure IPv4.
ipv6only
Only confgiure IPv6.
fqdn [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. dhcpcd itself
never does any DNS updates. dhcpcd encodes the FQDN hostname as
specified in RFC1035.
interface interface
Subsequent options are only parsed for this interface.
ipv6ra_fork
By default, when dhcpcd receives an IPv6 RA, dhcpcd will only
fork to the background if the RA contains at least one unexpired
RDNSS option. Set this option so to make dhcpcd always fork on
an RA.
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.
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.
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.
leasetime seconds
Request a leasetime of seconds.
metric metric
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.
noalias
IPv4 addresses added will overwrite a pre-existing address
instead of working alongside.
noarp Don't send any ARP requests. This also disables IPv4LL.
noauthrequired
Don't require authentication even though we requested it.
nodev Don't load /dev management modules.
nodhcp Don't start DHCP or listen to DHCP messages. This is only useful
when allowing IPv4LL.
nodhcp6
Don't start DHCPv6 or listen to DHCPv6 messages. Normally DHCPv6
is started by a RA instruction or configuration.
nogateway
Don't install any default routes.
nohook script
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
noipv4 Don't attempt to configure an IPv4 address.
noipv4ll
Don't attempt to obtain an IPv4LL address if we failed to get one
via DHCP. See RFC 3927.
noipv6 Don't attmept to configure an IPv6 address.
noipv6rs
Disable solicitation and receipt of IPv6 Router Advertisements.
nolink Don't receive link messages about carrier status. You should
only set this for buggy interface drivers.
option option
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 option
lines. Prepend dhcp6_ to option to request a DHCPv6 option.
DHCPv4 options are mapped to DHCPv6 where applicable.
nooption 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.
destination option
If 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.
profile name
Subsequent options are only parsed for this profile name.
quiet Suppress any dhcpcd output to the console, except for errors.
reboot seconds
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 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 autho‐
rative which means dhcpcd will timeout before moving back to the
DISCOVER phase.
release
dhcpcd will release the lease prior to stopping the interface.
require option
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 require dhcp_message_type.
script script
Use script instead of the default
/usr/lib/dhcpcd/dhcpcd-run-hooks.
ssid ssid
Subsequent options are only parsed for this wireless ssid.
static value
Configures a static value. If you set ip_address then 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.
interface eth0
static ip_address=192.168.0.10/24
static routers=192.168.0.1
static domain_name_servers=192.168.0.1
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.
interface ppp0
static ip_address=
destination routers
timeout seconds
Timeout after seconds, instead of the default 30. A setting of 0
seconds causes dhcpcd to wait forever to get a lease. If dhcpcd
is working on a single interface then dhcpcd will exit when a
timeout occurs, otherwise dhcpcd will fork into the background.
If using IPv4LL then dhcpcd start the IPv4LL process after the
timeout and then wait a little longer before really timing out.
userclass string
Tag the DHCPv4 messages with the userclass. You can specify more
than one.
vendor code,value
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.
vendor 01,192.168.0.2
Set the vendor option 02 with a hex code.
vendor 02,01:02:03:04:05
Set the vendor option 03 with an IP address as a string.
vendor 03,\"192.168.0.2\"
Set un-encapsulated vendor option to hello world.
vendor ,"hello world"
vendorclassid string
Set the DHCP Vendor Class. DHCPv6 has it's own option as shown
below. The default is dhcpcd-<version>:<os>:<machine>:<plat‐
form>. For example
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 imper‐
sonate Windows by using the MSFT vendorclassid.
vendclass en data
Add the DHCPv6 Vendor Indetifying Vendor Class with the IANA
assigned Enterprise Number en with the data. This option can be
set more than once to add more data, but the behaviour, as per
RFC(3925) is undefined if the Enterprise Number differs.
waitip [4 | 6]
Wait for an address to be assigned before forking to the back‐
ground. 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, dhcpcd.conf will wait for any address protocol to be
assigned. It is possible to wait for more than one address pro‐
tocol and dhcpcd.conf will only fork to the background when all
waiting conditions are satisfied.
xidhwaddr
Use the last four bytes of the hardware address as the DHCP xid
instead of a randomly generated number.
Defining new options
DHCP allows for the use of custom options. Each option needs to be
started with the define or define6 directive. This can optionally be
followed by both embed or encap options. Both can be specified more than
once and embed must come before encap.
define code type variable
Defines the DHCP option code of type with a name of variable
exported to dhcpcd-run-hooks(8).
define6 code type variable
Defines the DHCPv6 option code of type with a name of variable
exported to dhcpcd-run-hooks(8), with a prefix of _dhcp6.
vendopt code type variable
Defines the Vendor-Identifying Vendor Options. The code is the
IANA Enterprise Number which will unqiuely describe the encapsu‐
lated options. type is normally encap. variable names the Ven‐
dor option to be exported.
embed type variable
Defines an embedded variable within the defined option. The
length is determined by the type. If the variable is not the
same as defined in the parent option, it is prefixed with the
parent variable first with an underscore.
encap code type variable
Defines an encapsulated variable within the defined option. The
length is determined by the type. If the variable is not the
same as defined in the parent option, it is prefixed with the
parent variable first with an underscore.
Type prefix
These keywords come before the type itself, to describe it more fully.
You can use more than one, but they must appear in the order listed
below.
request Requests the option by default without having to be specified in
user configuration
norequest
This option cannot be requested, regardless of user configura‐
tion
index The option can appear more than once and will be indexed.
array The option data is split into a space seperated array, each ele‐
ment being the same type.
Types to define
The type directly affects the length of data consumed inside the option.
Any remaining data is normally discarded. Lengths can be specified for
string and binhex types, but this is generally with other data embedded
afterwards in the same option.
ipaddress
An IPv4 address, 4 bytes
ip6address
An IPv6 address, 16 bytes
string [: length]
A shell escaped string (binary data escaped as octal)
byte A byte
int16 A signed 16bit integer, 2 bytes
uint16 An unsigned 16bit integer, 2 bytes
int32 A signed 32bit integer, 4 bytes
uint32 An unsigned 32bit integer, 4 bytes
flag A fixed value (1) to indicate that the option is present, 0 bytes
domain A RFC 3397 encoded string
binhex [: length]
Binary data expressed as hexadecimal
embed Contains embedded options (implies encap as well)
encap Contains encapsulated options (implies embed as well)
option References an option from the global definition
Example definition
# DHCP option 81, Fully Qualified Domain Name, RFC4702
define 81 embed fqdn
embed byte flags
embed byte rcode1
embed byte rcode2
embed domain fqdn
# DHCP option 125, Vendor Specific Information Option, RFC3925
define 125 encap vsio
embed uint32 enterprise_number
# Options defined for the enterprise number
encap 1 ipaddress ipaddress
Supported protocols
token Sends and expects the token with the secretid 0 in each message.
delayedrealm
Delayed Authentication. dhcpcd will send an authentication
option with no key or MAC. The server will see this option, and
select a key for dhcpcd.conf, writing the realm and secretid in
it. dhcpcd will then look for a non-expired token with a match‐
ing realm and secretid. This token is used to authenicate all
other messages.
delayed Same as above, but without a realm.
Supported algorithms
If none specified, hmac-md5 is the default.
hmac-md5
Supported Replay Detection Mechanisms
If none specified, monotonic is the default. If this is changed from
what was previously used, or the means of calculating or storing it is
broken then the DHCP server will probably have to have its notion of the
clients Replay Detection Value reset.
monocounter
Read the number in the file /var/lib/dhcpcd/dhcpcd-rdm.monotonic
and add one to it.
monotime
Create a NTP timestamp from the system time.
monotonic
Same as monotime.
SEE ALSOfnmatch(3), if_nametoindex(3), dhcpcd(8), dhcpcd-run-hooks(8)AUTHORS
Roy Marples ⟨roy@marples.name⟩
BUGS
When configuring DHCPv6 you can only select one IA type. I can't think
of a use case where you would want different types, so if you have one
then please bring it up for discussion on the
⟨dhcpcd-discuss@marples.name⟩ mailing list.
Please report them to
http://roy.marples.name/projects/dhcpcd
BSD January 30, 2014 BSD
