dhcpcd man page on Manjaro

Man page or keyword search:  
man Server   11224 pages
apropos Keyword Search (all sections)
Output format
Manjaro logo
[printable version]

DHCPCD(8)		  BSD System Manager's Manual		     DHCPCD(8)

     dhcpcd — a DHCP client

     dhcpcd [-46ABbDdEGgHJKLMpqTV] [-C, --nohook hook] [-c, --script script]
	    [-e, --env value] [-F, --fqdn FQDN] [-f, --config file]
	    [-h, --hostname hostname] [-I, --clientid clientid]
	    [-i, --vendorclassid vendorclassid] [-l, --leasetime seconds]
	    [-m, --metric metric] [-O, --nooption option]
	    [-o, --option option] [-Q, --require option]
	    [-r, --request address] [-S, --static value]
	    [-s, --inform address[/cidr]] [-t, --timeout seconds]
	    [-u, --userclass class] [-v, --vendor code, value]
	    [-W, --whitelist address[/cidr]] [-w, --waitip [4 | 6]]
	    [-y, --reboot seconds] [-X, --blacklist address[/cidr]]
	    [-Z, --denyinterfaces pattern] [-z, --allowinterfaces pattern]
	    [interface] [...]
     dhcpcd -n, --rebind [interface]
     dhcpcd -k, --release [interface]
     dhcpcd -U, --dumplease interface
     dhcpcd --version
     dhcpcd -x, --exit [interface]

     dhcpcd is an implementation of the DHCP client specified in RFC 2131.
     dhcpcd gets the host information (IP address, routes, etc) from a DHCP
     server and configures the network interface of the machine on which it is
     running.  dhcpcd then runs the configuration script which writes DNS
     information to resolvconf(8), if available, otherwise directly to
     /etc/resolv.conf.	If the hostname is currently blank, (null) or local‐
     host, or force_hostname is YES or TRUE or 1 then dhcpcd sets the hostname
     to the one supplied by the DHCP server.  dhcpcd then daemonises and waits
     for the lease renewal time to lapse.  It will then attempt to renew its
     lease and reconfigure if the new lease changes when the lease beings to
     expire or the DHCP server sends message to renew early.

     dhcpcd is also an implementation of the BOOTP client specified in RFC

     dhcpcd is also an implementation of the IPv6 Router Solicitor as speci‐
     fied in RFC 4861 and RFC 6106.  dhcpcd can optionally handle address and
     route management itself, and will do so by default if Router Solicitation
     is disabled in the kernel.	 If dhcpcd is managing routes, dhcpcd sends
     Neighbor Solicitions to each advertising router periodically and will
     expire the ones that do not respond.

     dhcpcd is also an implemenation of the DHCPv6 client as specified in RFC
     3315.  By default, dhcpcd only starts DHCPv6 when instructed to do so by
     an IPV6 Router Advertisement.  If no Identity Association is configured,
     then a Non-temporary Address is requested.

   Local Link configuration
     If dhcpcd failed to obtain a lease, it probes for a valid IPv4LL address
     (aka ZeroConf, aka APIPA).	 Once obtained it restarts the process of
     looking for a DHCP server to get a proper address.

     When using IPv4LL, dhcpcd nearly always succeeds and returns an exit code
     of 0.  In the rare case it fails, it normally means that there is a
     reverse ARP proxy installed which always defeats IPv4LL probing.  To dis‐
     able this behaviour, you can use the -L, --noipv4ll option.

   Multiple interfaces
     If a list of interfaces are given on the command line, then dhcpcd only
     works with those interfaces, otherwise dhcpcd discovers available Ether‐
     net interfaces.  If any interface reports a working carrier then dhcpcd
     will try and obtain a lease before forking to the background, otherwise
     it will fork right away.  This behaviour can be modified with the -b,
     --background and -w, --waitip options.

     If a single interface is given then dhcpcd only works for that interface
     and runs as a separate instance.  The -w, --waitip option is enabled in
     this instance to maintain compatibility with older versions.

     Interfaces are preferred by carrier, DHCP lease/IPv4LL and then lowest
     metric.  For systems that support route metrics, each route will be
     tagged with the metric, otherwise dhcpcd changes the routes to use the
     interface with the same route and the lowest metric.  See options below
     for controlling which interfaces we allow and deny through the use of

   Hooking into events
     dhcpcd runs /usr/lib/dhcpcd/dhcpcd-run-hooks, or the script specified by
     the -c, --script option.  This script runs each script found in
     /usr/lib/dhcpcd/dhcpcd-hooks in a lexical order.  The default installa‐
     tion supplies the scripts 01-test, 10-mtu, 10-wpa_supplicant,
     15-timezone, 20-resolv.conf and 30-hostname.  You can disable each script
     by using the -C, --nohook option.	See dhcpcd-run-hooks(8) for details on
     how these scripts work.  dhcpcd currently ignores the exit code of the

   Fine tuning
     You can fine-tune the behaviour of dhcpcd with the following options:

     -b, --background
	     Background immediately.  This is useful for startup scripts which
	     don't disable link messages for carrier status.

     -c, --script script
	     Use this script instead of the default

     -D, --duid
	     Generate an RFC 4361 compliant clientid.  This requires persis‐
	     tent storage and not all DHCP servers work with it so it is not
	     enabled by default.  dhcpcd generates the DUID and stores it in
	     /etc/dhcpcd.duid.	This file should not be copied to other hosts.

     -d, --debug
	     Echo debug messages to the stderr and syslog.

     -E, --lastlease
	     If dhcpcd cannot obtain a lease, then try to use the last lease
	     acquired for the interface.  If the -p, --persistent option is
	     not given then the lease is used if it hasn't expired.

     -e, --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 -e force_hostname=YES.

     -g, --reconfigure
	     dhcpcd will re-apply IP address, routing and run
	     dhcpcd-run-hooks(8) for each interface.  This is useful so that a
	     3rd party such as PPP or VPN can change the routing table and /
	     or DNS, etc and then instruct dhcpcd to put things back after‐
	     wards.  dhcpcd does not read a new configuration when this hap‐
	     pens - you should rebind if you need that functionality.

     -F, --fqdn fqdn
	     Requests that the DHCP server updates DNS using FQDN instead of
	     just a hostname.  Valid values for fqdn are disable, none, ptr
	     and both.	dhcpcd itself never does any DNS updates.  dhcpcd
	     encodes the FQDN hostname as specified in RFC1035.

     -f, --config file
	     Specify a config to load instead of /etc/dhcpcd.conf.  dhcpcd
	     always processes the config file before any command line options.

     -h, --hostname hostname
	     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.

     -I, --clientid clientid
	     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.

     -i, --vendorclassid vendorclassid
	     Override the DHCPv4 vendorclassid field sent.  The default is
	     dhcpcd-<version>:<os>:<machine>:<platform>.  For example
	     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.

     -k, --release [interface]
	     This causes an existing dhcpcd process running on the interface
	     to release its lease and de-configure the interface.  If no
	     interface is specified then this applies to all interfaces.  If
	     no interfaces are left running, dhcpcd will exit.

     -l, --leasetime seconds
	     Request a specific lease time in seconds.	By default dhcpcd does
	     not request any lease time and leaves it in the hands of the DHCP

     -M, --master
	     Start dhcpcd in master mode even if only one interface specified
	     on the command line.

     -m, --metric metric
	     Metrics are used to prefer an interface over another one, lowest
	     wins.  dhcpcd will supply a default metic of 200 +
	     if_nametoindex(3).	 An extra 100 will be added for wireless

     -n, --rebind [interface]
	     Notifies dhcpcd to reload its configuration and rebind the speci‐
	     fied interface.  If no interface is specified then this applies
	     to all interfaces.	 If dhcpcd is not running, then it starts up
	     as normal.	 This may also cause wpa_supplicant(8) to reload its
	     configuration for each interface as well.

     -o, --option option
	     Request the DHCP option variable for use in

     -p, --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.

     -r, --request [address]
	     Request the address in the DHCP DISCOVER message.	There is no
	     guarantee this is the address the DHCP server will actually give.
	     If no address is given then the first address currently assigned
	     to the interface is used.

     -s, --inform [address[/cidr]]
	     Behaves like -r, --request as above, but sends a DHCP INFORM
	     instead of DISCOVER/REQUEST.  This does not get a lease as such,
	     just notifies the DHCP server of the address in use.  You should
	     also include the optional cidr network number in case the address
	     is not already configured on the interface.  dhcpcd remains run‐
	     ning and pretends it has an infinite lease.  dhcpcd will not de-
	     configure the interface when it exits.  If dhcpcd fails to con‐
	     tact a DHCP server then it returns a failure instead of falling
	     back on IPv4LL.

     -S, --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
		   dhcpcd -S ip_address= \
		   -S routers= \
		   -S domain_name_servers= \

     -t, --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.

     -u, --userclass class
	     Tags the DHCPv4 message with the userclass class.	DHCP servers
	     use this to give members of the class DHCP options other than the
	     default, without having to know things like hardware address or

     -v, --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.
		   dhcpcd -v 01, eth0
	     Set the vendor option 02 with a hex code.
		   dhcpcd -v 02,01:02:03:04:05 eth0
	     Set the vendor option 03 with an IP address as a string.
		   dhcpcd -v 03,\"\" eth0
	     Set un-encapsulated vendor option to hello world.
		   dhcpcd -v ,"hello world" eth0

	     Display both program version and copyright information.  dhcpcd
	     then exits before doing any configuration.

     -w, --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 will wait for any address protocol to be assigned.
	     It is possible to wait for more than one address protocol and
	     dhcpcd will only fork to the background when all waiting condi‐
	     tions are satisfied.

     -x, --exit [interface]
	     This will signal an existing dhcpcd process running on the
	     interface to de-configure the interface and exit.	If no inter‐
	     face is specified, then the above is applied to all interfaces.
	     dhcpcd then waits until this process has exited.

     -y, --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.

   Restricting behaviour
     dhcpcd will try to do as much as it can by default.  However, there are
     sometimes situations where you don't want the things to be configured
     exactly how the the DHCP server wants.  Here are some options that deal
     with turning these bits off.

     -4, --ipv4only
	     Only configure IPv4.

     -6, --ipv6only
	     Only confgiure IPv6.

     -A, --noarp
	     Don't request or claim the address by ARP.	 This also disables

     -B, --nobackground
	     Don't run in the background when we acquire a lease.  This is
	     mainly useful for running under the control of another process,
	     such as a debugger or a network manager.

     -C, --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:-
		   dhcpcd -C resolv.conf -C mtu eth0

     -G, --nogateway
	     Don't set any default routes.

     -H, --xidhwaddr
	     Use the last four bytes of the hardware address as the DHCP xid
	     instead of a randomly generated number.

     -J, --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 instances, dhcpcd will
	     set this automatically.

     -K, --nolink
	     Don't receive link messages for carrier status.  You should only
	     have to use this with buggy device drivers or running dhcpcd
	     through a network manager.

     -L, --noipv4ll
	     Don't use IPv4LL (aka APIPA, aka Bonjour, aka ZeroConf).

     -O, --nooption option
	     Don't request the specified option.  If no option given, then
	     don't request any options other than those to configure the
	     interface and routing.

     -Q, --require option
	     Requires the option to be present in all DHCP messages, otherwise
	     the message is ignored.  To enforce that dhcpcd only responds to
	     DHCP servers and not BOOTP servers, you can -Q dhcp_message_type.

     -q, --quiet
	     Quiet dhcpcd on the command line, only warnings and errors will
	     be displayed.  The messages are still logged though.

     -T, --test
	     On receipt of DHCP messages just call
	     /usr/lib/dhcpcd/dhcpcd-run-hooks with the reason of TEST which
	     echos the DHCP variables found in the message to the console.
	     The interface configuration isn't touched and neither are any
	     configuration files.  To test INFORM the interface needs to be
	     configured with the desired address before starting dhcpcd.

     -U, --dumplease interface
	     Dumps the last lease for the interface to stdout.	interface
	     could also be a path to a DHCP wire formatted file.

     -V, --variables
	     Display a list of option codes and the associated variable for
	     use in dhcpcd-run-hooks(8).  Variables are prefixed with new_ and
	     old_ unless the option number is -.  Variables without an option
	     are part of the DHCP message and cannot be directly requested.

     -W, --whitelist address[/cidr]
	     Only accept packets from address[/cidr].  -X, --blacklist is
	     ignored if -W, --whitelist is set.

     -X, --blacklist address[/cidr]
	     Ignore all packets from address[/cidr].

     -Z, --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).

     -z, --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 -Z,
	     --denyinterfaces then it is still denied.

	     Don't load any /dev management modules.

     Some interfaces require configuration by 3rd parties, such as PPP or VPN.
     When an interface configuration in dhcpcd is marked as STATIC or INFORM
     without an address then dhcpcd will monitor the interface until an
     address is added or removed from it and act accordingly.  For point to
     point interfaces (like PPP), a default route to its destination is auto‐
     matically added to the configuration.  If the point to point interface is
     configured for INFORM, then dhcpcd unicasts INFORM to the destination,
     otherwise it defaults to STATIC.

     dhcpcd requires a Berkley Packet Filter, or BPF device on BSD based sys‐
     tems and a Linux Socket Filter, or LPF device on Linux based systems for
     all IPv4 configuration.

     Configuration file for dhcpcd.  If you always use the same options, put
     them here.

     Text file that holds the DUID used to identify the host.

     Bourne shell script that is run to configure or de-configure an inter‐

     /dev management modules.

     A directory containing bourne shell scripts that are run by the above
     script.  Each script can be disabled by using the -C, --nohook option
     described above.

     The actual DHCP message sent by the server.  We use this when reading the
     last lease and use the files mtime as when it was issued.

     The actual DHCPv6 message sent by the server.  We use this when reading
     the last lease and use the files mtime as when it was issued.

     Stores the monotonic counter used in the replay field in Authentication

     Stores the PID of dhcpcd running on all interfaces.

     Stores the PID of dhcpcd running on the interface.

     Control socket to the master daemon.

     Control socket to per interface daemon.

     fnmatch(3), if_nametoindex(3), dhcpcd.conf(5), resolv.conf(5),
     dhcpcd-run-hooks(8), resolvconf(8)

     RFC 951, RFC 1534, RFC 2104, RFC 2131, RFC 2132, RFC 2563, RFC 2855,
     RFC 3004, RFC 3118, RFC 3203, RFC 3315, RFC 3361, RFC 3633, RFC 3396,
     RFC 3397, RFC 3442, RFC 3495, RFC 3925, RFC 3927, RFC 4039, RFC 4075,
     RFC 4242, RFC 4361, RFC 4390, RFC 4702, RFC 4074, RFC 4861, RFC 4833,
     RFC 5227, RFC 5942, RFC 5969, RFC 6106, RFC 6334, RFC 6704.

     Roy Marples ⟨roy@marples.name⟩

     Please report them to

BSD				 March 7, 2014				   BSD

List of man pages available for Manjaro

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
Vote for polarhome
Free Shell Accounts :: the biggest list on the net