| DHCPCD(8) | System Manager's Manual | DHCPCD(8) |
dhcpcd —
dhcpcd |
[-146ABbDdEGgHJKLMNPpqTV-C,
--nohook
hook-c,
--script
script-e,
--env
value-F,
--fqdn
FQDN-f,
--config
file-h,
--hostname
hostname-I,
--clientid
clientid-i,
--vendorclassid
vendorclassid-j,
--logfile
logfile-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[ ]/broadcast_address ]--inform6-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--inactiveinterface ] [... ] |
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 localhost, 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.
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.
dhcpcd is also an implementation of the BOOTP
client specified in RFC 951.
dhcpcd is also an implementation of the IPv6
Router Solicitor as specified in RFC 4861 and
RFC 6106.
dhcpcd is also an implementation of the IPv6
Privacy Extensions to AutoConf as specified in RFC
4941. This feature needs to be enabled in the kernel and
dhcpcd will start using it.
dhcpcd is also an implementation 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.
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 disable this behaviour, you can use the
-L,
--noipv4ll
option.
dhcpcd only works with those interfaces,
otherwise dhcpcd discovers available
Ethernet interfaces that can be configured. When
dhcpcd not limited to one interface on the
command line, it is running in Master mode. The
dhcpcd-ui project expects dhcpcd to be
running this way.
If a single interface is given then dhcpcd
only works for that interface and runs as a separate instance to other
dhcpcd processes.
-w,
--waitip
option is enabled in this instance to maintain compatibility with older
versions. Using a single interface also affects the
-k, -N,
-n and
-x options where the same interface will
need to be specified as a lack of an interafce will imply Master mode which
this is not. To force starting in Master mode with only one interface, the
-M,
--master
option can be used.
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
patterns.
dhcpcd runs
/usr/libexec/dhcpcd-run-hooks, or the
script specified by the -c,
--script
option. This script runs each script found in
/usr/libexec/dhcpcd-hooks in a lexical
order. The default installation supplies the scripts
01-test,
02-dump,
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 script.
More scripts are supplied in
/usr/share/dhcpcd/hooks and need to be
copied to /usr/libexec/dhcpcd-hooks if you
intend to use them. For example, you could install
10-wpa_supplicant so that
dhcpcd can ensure that
wpa_supplicant(8) is
always running on a hot-plugged wireless interface.
dhcpcd
with the following options:
-b,
--background-c,
--script
script-D,
--duid-I,
--clientid.
The DUID generated will be held in
/var/db/dhcpcd/duid and should not be
copied to other hosts. This file also takes precedence over the above
rules.-d,
--debug-E,
--lastleasedhcpcd cannot obtain a lease, then
try to use the last lease acquired for the interface.--lastleaseextenddhcpcd will give it up if any other
host tries to claim it for their own via ARP. This is does violate RFC2131
section 3.7 which states the lease should be dropped once it has
expired.-e,
--env
value-e
force_hostname=YES.-g,
--reconfiguredhcpcd 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 afterwards.
dhcpcd does not read a new
configuration when this happens - you should rebind if you need that
functionality.-F,
--fqdn
fqdndhcpcd
itself never does any DNS updates.
dhcpcd encodes the FQDN hostname as
specified in RFC1035.-f,
--config
filedhcpcd always processes the config file
before any command line options.-h,
--hostname
hostname-I,
--clientid
clientiddhcpcd sends a default
clientid of the hardware family and the
hardware address.-i,
--vendorclassid
vendorclassid-j,
--logfile
logfiledhcpcd receives the
SIGUSR2 signal.-k,
--release
[dhcpcd process
running on the interface to release its
lease and de-configure the interface
regardless of the -p,
--persistent
option. If no interface is specified then
this applies to all interfaces in Master mode. If no interfaces are left
running, dhcpcd will exit.-l,
--leasetime
secondsdhcpcd does not request any
lease time and leaves it in the hands of the DHCP server.-M,
--masterdhcpcd in Master mode even if
only one interface specified on the command line. See the Multiple
Interfaces section above.-m,
--metric
metricdhcpcd will supply a default metic of
200 +
if_nametoindex(3).
An extra 100 will be added for wireless interfaces.-n,
--rebind
[dhcpcd to reload its
configuration and rebind the specified
interface. If no
interface is specified then this applies
to all interfaces in Master mode. 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 if the relevant hook
script has been installed.-N,
--renew
[dhcpcd to renew existing
addresses on the specified interface. If
no interface is specified then this
applies to all interfaces in Master mode. If
dhcpcd is not running, then it starts
up as normal. Unlike the -n,
--rebind
option above, the configuration for
dhcpcd is not reloaded.-o,
--option
option-p,
--persistentdhcpcd 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-s,
--inform
address[-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 running and pretends it
has an infinite lease. dhcpcd 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.--inform6dhcpcd is not processing IPv6RA
messages and the need for DHCPv6 Information Request exists.-S,
--static
valueip_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.
-e,
-
-env option instead.-t,
--timeout
secondsdhcpcd 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.-u,
--userclass
class-v,
--vendor
code,value--versiondhcpcd then exits before doing any
configuration.-w--waitip
[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 conditions are satisfied.-x,
--exit
[dhcpcd
process running on the interface to exit.
If no interface is specified, then the
above is applied to all interfaces in Master mode. See the
-p,
-
-persistent option to control
configuration persistence on exit, which is enabled by default in
dhcpcd.conf(5).
dhcpcd then waits until this process
has exited.-y,
--reboot
secondsdhcpcd to skip the reboot phase and go
straight into discover. This has no effect on DHCPv6 other than skipping
the reboot phase.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.
Note that when dhcpcd is restricted to a
single interface then the interface also needs to be specified when asking
dhcpcd to exit using the commandline. If
the protocol is restricted as well then the protocol needs to be included with
the exit instruction.
-1,
--oneshot-w,
-
-waitip option to specify which
protocol(s) to configure before exiting.-4,
--ipv4only-6,
--ipv6only-A,
--noarp-B,
--nobackground-C,
--nohook
scriptdhcpcd from touching your DNS
settings you would do:-
-G,
--nogateway-H,
--xidhwaddr-J,
--broadcastdhcpcd will set this
automatically.-K,
--nolinkdhcpcd through a network manager.-L,
--noipv4ll-O,
--nooption
option-P,
--printpidfiledhcpcd will use based on commmand-line
arguments to stdout.-Q,
--require
optiondhcpcd only responds to DHCP servers
and not BOOTP servers, you can -Q
dhcp_message_type.-q,
--quietdhcpcd on the command line, only
warnings and errors will be displayed. The messages are still logged
though.-T,
--testdhcpcd.-U,
--dumplease
interface-4 or
-6 flags to specify an address
family.-V,
--variables-W,
--whitelist
address[-X,
-
-blacklist is ignored if
-W,
-
-whitelist is set.-X,
--blacklist
address[-Z,
--denyinterfaces
pattern-z,
--allowinterfaces
pattern-Z,
--denyinterfaces
then it is still denied.--inactivedhcpcd to be started in
Master mode and then wait for subsequent
dhcpcd commands to start each interface
as required.--nodevdhcpcd 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 automatically
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 systems and a Linux Socket Filter, or LPF device on
Linux based systems for all IPv4 configuration.
If restricting dhcpcd to a single interface
and optionally address family via the command-line then all further calls to
dhcpcd to rebind, reconfigure or exit need
to include the same restrictive flags so that
dhcpcd knows which process to signal.
Some DHCP servers implement ClientID filtering. If
dhcpcd is replacing an in-use DHCP client
then you might need to adjust the clientid option
dhcpcd sends to match. If using a DUID in
place of the ClientID, edit
/var/db/dhcpcd/duid accordingly.
-C,
-
-nohook option described above.dhcpcd running on all
interfaces.dhcpcd running on the
interface.| June 5, 2018 | x86_64 |