Runs in background(server) and sets configuration OR
sends commands to the server.

dhcpcd.conf

dhcpcd configuration file

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.
Escape characters in the value using the \ character.
Comments can be prefixed with the # character.
String values should be quoted with the " character.

`debug`	Echo debug messages to the stderr and syslog.
`background`	Background immediately. For startup scripts which don't disable link messages for carrier status.
`logfile logfile`	Writes to logfile rather than syslog. Truncated when opened and is reopened when receives `SIGUSR2`
`controlgroup group`	Sets the group ownership of `/var/run/dhcpcd.sock`
`bootp`	Be a BOOTP client, don't send a DHCP Message Type option and only interact with a BOOTP server. Other options still available.
`persistent`	Supresses 'De-configuring' on exit.
Restrict Configuration
`ipv4only`	Only configure IPv4
`ipv6only`	Only confgiure IPv6.
`nodhcp`	Don't start DHCP or listen to DHCP messages. Useful when allowing IPv4LL.
`nodhcp6`	Don't start DHCPv6 or listen to DHCPv6 messages. Normally DHCPv6 is started by a RA instruction or configuration.
`allowinterfaces patternList`	`patternList` a space or comma separated list . Only interfaces that match. `denyinterfaces` superceeds.
`-Z --denyinterfaces patternList`	Only interfaces that do not match
`broadcast`	broadcast replies back to the client.
`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.
Per interface
`interface interface`	Subsequent options are only parsed for this interface.
`dhcp`	Enable DHCP , on by default.
`dhcp6`	Enable DHCPv6 , on by default.
`noipv4`	Enable IPv4 , on by default.
`noipv6`	Enable IPv6 , on by default.
`arping address [address]`	dhcpcd will arping each address in order before DHCP. If an address is found, the replying hardware address as the profile, otherwise the ip address. Example: interface bge0 arping 192.168.0.1 # My specific 192.168.0.1 network profile dd:ee:aa:dd:bb:ee static ip_address=192.168.0.10/24 # A generic 192.168.0.1 network profile 192.168.0.1 static ip_address=192.168.0.98/24
`noarp`	Don't send any ARP requests. This also disables IPv4LL.
`leasetime seconds`
`metric metric`	default metric is 200 + if_nametoindex(3) + (100 for wireless interfaces). Metrics are used to prefer an interface over another one, lowest wins.
`authprotocol protocol algorithm rdm`	Authenticate DHCP messages. See the Supported Authentication 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` date the token expires formatted "yyy-mm-dd HH:MM" or `forever` For the token protocol, `secretid` must be 0 and `realm` "". Error: `dhcp_auth_encode: Invalid argument` means the correct authentication token was not found in the configuration.
`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 set which driver wpa_supplicant(8) should use with `env wpa_supplicant_driver=nl80211` To force the hostname hook to set the hostname use `env force_hostname=YES`, If the hostname is set, it will be will set to the FQDN . If the FQDN option is missing, dhcpcd will 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 what the server provides. 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 send a default clientid of the hardware family and the hardware address.
`duid`	Generate an RFC 4361. compliant DHCP Unique Identifier. If persistent 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. Must be used in an interface block. defaults to the last 4 bytes of the hardware address assigned to the interface. Eachs instance of this should be unique within the scope of the client and dhcpcd warns if a conflict is detected. If there is a conflict, it is only a problem if the conflicted IAIDs are used on the same network.
`request [address]`	Request the address in a `DHCP DISCOVER` message. There is no guarantee the DHCP server will give it. If no address is given then the first address currently assigned to the interface is used.
`inform [address[/cidr]]`	Like `request`, but sends a `DHCP INFORM` instead of DISCOVER/REQUEST. This does not get a lease rather notifies the DHCP server of the address in use. include the optional cidr network number in case the address is not already configured on the interface. Performs as if it has an infinite lease and will not de-configure the interface when it exits. If dhcpcd fails to contact a DHCP server then it returns a failure instead of falling back on IPv4LL.
`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 dhcpcd is not processing IPv6RA messages and the need for DHCPv6 Information Request exists.
`fallback profile`	Fallback to using this profile if DHCP fails. This allows you to configure a static profile instead of using Zero-Conf.
`hostname name`	Sends the hostname so it can be registered in DNS. If `name` is an empty, the system hostname is sent. If `name` 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. Useful because DHCP servers will not register the FQDN in their DNS if the domain part does not match theirs. see `env` to control how the hostname is set on the host.
`ia_na [iaid [/ address]]`	Request a DHCPv6 Normal Address for iaid. more than one ia_na by specifying a unique iaid for each one.
`ia_ta [iaid]`	Request a DHCPv6 Temporary` Address for iaid.
`ia_pd [iaid [/ prefix / prefix_len] [interface [/ sla_id [/ prefix_len [/ suffix]]]]]`	Request a DHCPv6 Delegated Prefix for iaid. Must be used in an interface block. Unless a sla_id of 0 is assigned with the same resultant prefix length as the delegation, a reject route is installed for the Delegated Prefix to stop unallocated addresses being resolved upstream. If no interface is given then we will assign a prefix to every other interface with a sla_id equivalent to the interface index assigned by the OS. Otherwise addresses are only assigned for each interface and sla_id. Each assigned address will have a suffix, defaulting to 1. If the suffix is 0 then a slaac address is assigned. You cannot assign a prefix to the requesting interface unless the DHCPv6 server supports RFC6603 Prefix Exclude Option. dhcpcd has to be running for all the interfaces it is delegating to. A default prefix_len of 64 is assumed, unless the maximum sla_id does not fit. In this case prefix_len is increased to the highest multiple of 8 that can accommodate the sla_id. sla_id is an integer which must be unique inside the iaid 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. In the following example `eth0` is configured for both IPv4 and IPv6. The DHCPv4 server will provide an IPv4 address and a default route. The DHCPv6 server will provide an IPv6 address, a default route and a /64 subnet to be delegated to the internal interface. `eth1` will be configured for IPv6 using the first address (::1) from the delegated prefix. Two other interfaces will be assined a second prefix to rtadvd(8) can be used with an empty configuration file on eth1, eth2 and eth3, to provide automatic IPv6 address configuration for the internal network. noipv6rs # disable routing solicitation denyinterfaces eth2 # Don't touch eth2 at all interface eth0 ipv6rs # enable routing solicitation get the default IPv6 route ia_na 1 # request an IPv6 address ia_pd 2 eth1/0 # request a PD and assign it to eth1 ia_pd 3 eth2/1 eth3/2 # req a PD and assign it to eth2 and eth3
`fqdn [ disable \| ptr \| both]`	`disable` will disable the FQDN option. `ptr` reqeusts the DHCP server to update the PTR record of the host in DNS `both` also updates the A record. The default is `both`.
`ipv6ra_autoconf`	Generate SLAAC addresses for each Prefix advertised by a Router Advertisement message with the Auto flag set. On by default.
`ipv6ra_noautoconf`
`ipv6ra_fork`	Always fork to background on an RA. By default, when dhcpcd receives an IPv6 RA, forks to the background if the RA contains at least one unexpired RDNSS option and a valid prefix or no DHCPv6 instruction.
`ipv6ra_own`	Disables kernel IPv6 RAprocessing so dhcpcd can manage addresses and routes.
`ipv6ra_own_default`	When dhcpcd receives an IPv6 RA, 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.
`ipv6rs`	Enables IPv6 RA solicitation. On by default, unless disabled globally.
`noalias`	IPv4 addresses will be removed from the interface when adding a new IPv4 address.
`noauthrequired`	Don't require authentication including for `FORCERENEW and RECONFIGURE`
`nodelay`	Don't delay for an initial randomised time when starting protocols.
`nodev`	Don't load /dev management modules.
`nogateway`	don't Install a default route (default).
`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 modifying DNS settings or starting `wpa_supplicant` use `nohook resolv.conf, wpa_supplicant`
`noipv4ll`	Don't to obtain an IPv4LL address if failed to get one via DHCP. See RFC 3927.
`noipv6rs`	Disable solicitation and receipt of IPv6 Router Advertisements.
`nolink`	Don't receive link messages about carrier status. only set this for buggy interface drivers.
`noup`	Don't bring the interface up when in master mode. If dhcpcd.conf cannot determine the carrier state, `dhcpcd.conf` will enter a tight polling loop until the interface is marked up and running or a valid carrier state is reported.
`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. option Prepend `dhcp6_` to option to request a DHCPv6 option. If no DHCPv6 options are configured, then DHCPv4 options are mapped to equivalent DHCPv6 options. Prepend `nd_ to` option to handle ND options, only for the nooption, reject and require options. To list options use dhcpcd with the -V, --variables argument.
`nooption option`	Remove the option from the message before it's processed.
`require option`	`option` is required in all messages, otherwise the message is ignored. To enforce that dhcpcd only responds to DHCP servers and not BOOTP servers, require dhcp_message_type. a `BOOTP` server can send DHCP like options.
`reject option`	Reject a message that contains `option`. Useful when you cannot use `require` to select / de-select BOOTP messages.
`destination option`	If dhcpcd.conf detects an address added to a point-to-point interface (PPP, TUN, etc) it will set the options to the destination address of the interface.
`profile name`	Subsequent options are only parsed for this profile name.
`ssid ssid`	Subsequent options are only parsed for this wireless ssid.
`reboot seconds`	Allow `seconds` before moving to the DISCOVER phase with an old lease to use and moving from DISCOVER to IPv4LL if no reply. The default is 5 seconds. 0 causes dhcpcd to skip the REBOOT phase and go into DISCOVER.
`release`	releases the lease prior to stopping the interface.
`script script`	default `/lib/dhcpcd/dhcpcd-run-hooks.`
`slaac [hwaddr \| private]`	interface identifier used for SLAAC generated IPv6 addresses. For `private` is used, a RFC7217 address is generated.
`static value`	Configures a static value. For ip6_address, dhcpcd will continue auto-configuation as normal. Example which configures two static address, an IPv4 router, DNS server and disables IPv6 auto-configuration. Use `inform6` to obtain more information via DHCPv6. For IPv4 use the inform ipaddress option instead of setting a static address. interface eth0 noipv6rs static ip_address=192.168.0.10/24 static ip6_address=fd51:42f8:caae:d92e::ff/64 static routers=192.168.0.1 static domain_name_servers=192.168.0.1 fd51:42f8:caae:d92e::1 Example for PPP which gives the destination a default route. It uses `destination` to insert the destination address into the value. interface ppp0 static ip_address= destination routers
`timeout seconds`	default 30. (don't use 0 which would causes dhcpcd to wait forever to get a lease.) If working on a single interface exits when a timeout occurs, otherwise fork into the background. With IPv4LL start the IPv4LL process after the timeout and then waits longer before really timing out.
`userclass string`	Tag the DHCPv4 messages with the userclass. can be specifed more than once.
`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. vendor 01,192.168.0.2 # Set the vendor option 01 with an IP address. vendor 02,01:02:03:04:05 # Set the vendor option 02 with a hex code. vendor 03,\"192.168.0.2\" # Set the vendor option 03 with an IP address as a string. vendor ,"hello world" # Set un-encapsulated vendor option to 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:platform`>. For example dhcpcd-5.5.6:NetBSD-6.99.5:i386:i386 If not set then none is sent. Some DHCP servers reject unknown vendorclassids. To work around it, try 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, the behaviour, is undefined if the Enterprise Number differs.
`waitip [4 \| 6]`	Wait for an address before forking to the background. Default any, 4 an IPv4 address , 6 an IPv6 address . Multiples are permitted
`xidhwaddr`	Use last four bytes of the hardware address as the DHCP xid instead of a random number.
`quiet`	Suppress output except errors.

Defining new options

DHCP, ND and DHCPv6 allow for the use of custom options. Each option needs to be started with

 define, infinity or
     define6

, optionally be followed by both embed or encap. If both are specified embed must come before encap.

`define code type variable`	exported to dhcpcd-run-hooks(8).
`definend code type variable`	" … " with a prefix of `_nd.`
`define6 code type variable`	DHCPv6 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 encapsulated options. `type` is normally `encap variable` names the Vendor option to be exported.
`embed type variable`	within the defined option. If the variable is not the same as defined in the parent option, it is prefixed with the parent variable first with an underscore. If the variable has the name of reserved then it is not processed.
`encap code type variable`	within the defined option. 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 they must appear in the order listed.

`request`	Requests the option by default without having to be specified in user configuration
`norequest`	This option cannot be requested, regardless of user configuration
`optional`	This option is optional. Only makes sense for embedded options where like the client FQDN option where the FQDN string itself is optional.
`index`	The option can appear more than once and will be indexed.
`array`	The option data is split into a space separated array, each element being the same type.

The type defines the data consumed, remaining data is discarded.

`ipaddress`	An IPv4 address, 4 bytes.
`ip6address`	An IPv6 address, 16 bytes.
`string [: length]`	A NVT ASCII string of printable characters.
`byte`	A byte.
`bitflags: flags`	A byte represented as a string of flags, most significant bit first. For example, using ABCDEFGH then A would equal 10000000, B 01000000, C 00100000, etc. If the bit is not set, the flag is not printed. A flag of 0 is not printed even if the bit postition is set. This is to allow reservation of the first bits while assinging the last bits.
`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.
`dname`	A RFC 1035 validated 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 Authentication Protocols

token	Sends and expects the token with the secretid 0 and realm of "" 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 matching realm and secretid. This token is used to authenicate all other messages.
delayed	Same as above, but without a realm.

Supported Authentication Algorithms

If none specified, hmac-md5 is the default. hmac-md5

Supported Replay Detection Mechanisms

`monotime monotonic`		Create a NTP timestamp from the system time.
`none`	If this is changed or the means of calculating or storing it is broken the DHCP server will have its notion of the clients Replay Detection Value
`monocounter`	Read the number in `/var/lib/dhcpcd5/dhcpcd-rdm.monotonic` and add one to it.

SEE ALSO fnmatch(3), if_nametoindex(3), dhcpcd(8), dhcpcd-run-hooks(8)

`interface`	network interface. Default `eth0`
`-L ConfigDir`	`ConfigDir` instead of `/etc/dhcpc`
`-c` `ExecFilePath`	Uses `ExecFilePath` instead of `ConfigDir/dhcpcd.exe`
`-T script`	Test case. Goes through the DHCP negotiation sequence but doesn't configure the interface. Uses `ConfigDir/dhcpcd.exe script`s. Writes `ConfigDir/dhcpcd-interface.info` and `ConfigDir`/dhcpcd-`interface`.cache.
`-B`	Requests broadcast .
`-n`	Send `SIGALRM` to renew the lease, if not running the startup procedure.
`-H hostname`	Set hostname option supplied by DHCP server. By default don't set hostname
`-D`	Set domainname as supplied by DHCP server. Default don't set domainname
`-Y`	Don't replace `/etc/yp.conf` . Domainname is not updated unless `-D` is specified.
`-R`	Don't replace `/etc/resolv.conf`
`-N`	Don't replace existing `/etc/ntp.conf`
`-h` `hostname`	Use `hostname` for option field when sending messages.
`-i vendorClassID`	vendor class identifier .
`-I ClientID`	client identifier . Default MAC address
`-l leasetime`	Suggest lease time (seconds) to the server. (server can override this ). Used in the `DHCP_DISCOVER` message. The default is infinite (0xFFFFFFFF).
`-G [gateway]`	`gateway` address for default route. Without `gateway` no Default routes are installed.
`-s` `[ipaddr]`	Send `DHCP_INFORM` to server using ipaddr in the form xxx.xxx.xxx.xxx. Without ipaddr, uses the address currently assigned to the interface. If no address is assigned, use previously obtained address from `ConfigDir/dhcpcd-interface.cache`
`-S`	Send second `DHCP_DISCOVER` after receiving `DHCP_OFFER`
`-k`	Sends `SIGHUP` to the running `dhcpcd` which sends `DCHP_RELEASE` to the server and destroys its cache. `SIGTERM` used by `shutdown` will not send `DHCP_RELEASE` and will not destroy cache. After the system boots cache is used to request the same address from server.
`-r`	Makes dhcpcd RFC1541 (obsolete) compliant. is RFC2131 compliant otherwise.
`-C`	Checksum received packets.
`-w windowsize`	window size for the gateway route. Default=32768.
Become server
`-t timeout`	Seconds to wait for an IP address. default 60 . Forks to background after getting an address and becomes the server If timeout expires returns 1.

`/etc/dhcpc`	Default `ConfigDir` directory used for storing files See `-L ConfigDir`.
`ConfigDir/dhcpcd-interface.info`	host information.
`ConfigDir/dhcpcd-interface.pid`	Contains the process id
`ConfigDir/dhcpcd.exe`	Scripts to execute when it configures or brings down the interface. Parameters passed to `dhcpcd.exe` script: `dhcpcd.exe HostInfoFilePath HostInfoFilePath is path to dhcpcd-interface.info. interface is the interface name dhcpcd is attached to.` `up\|down\|new The interface has been brought up with the same address, with a new IP address or brought down.` `-d is passed if started with -d debug`
`ConfigDir/dhcpcd-interface.cache`	contains the previously assigned IP address etc. `interface` is the network interface name for example: `eth0` to which `dhcpcd` is attached.
`/etc/resolv.conf`	Created when the client receives DNS and domain name options after renaming the old file to `/etc/resolv.conf.sv` and restored when `dhcpcd` exits for any reason.
`/etc/yp.conf`	created when the client receives NIS options. … and restored when `dhcpcd` exits for any reason.
`/etc/ntp.conf`	created when the client receives <>b>NTP options. The old file is renamed to `/etc/ntp.conf.sv`

DHCPcd

client

linux

Hooking into events

Local Link configuration

3RD Party Link Management

FILES

See

DHCPD

Dynamic Host Configuration Protocol DEAMON

Become server

FILES

See

Examples

dhcpcd.conf

dhcpcd configuration file

Restrict Configuration

Per interface

Defining new options

Type prefix

Supported Authentication Protocols

Supported Authentication Algorithms

Supported Replay Detection Mechanisms

/etc/resolv.conf

/etc/dhcpcd.conf