.\" Copyright (c) 2006-2015 Roy Marples .\" All rights reserved .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .Dd March 17, 2015 .Dt DHCPCD 8 .Os .Sh NAME .Nm dhcpcd .Nd a DHCP client .Sh SYNOPSIS .Nm .Op Fl 46ABbDdEGgHJKLMpqTV .Op Fl C , Fl Fl nohook Ar hook .Op Fl c , Fl Fl script Ar script .Op Fl e , Fl Fl env Ar value .Op Fl F , Fl Fl fqdn Ar FQDN .Op Fl f , Fl Fl config Ar file .Op Fl h , Fl Fl hostname Ar hostname .Op Fl I , Fl Fl clientid Ar clientid .Op Fl i , Fl Fl vendorclassid Ar vendorclassid .Op Fl j , Fl Fl logfile Ar logfile .Op Fl l , Fl Fl leasetime Ar seconds .Op Fl m , Fl Fl metric Ar metric .Op Fl O , Fl Fl nooption Ar option .Op Fl o , Fl Fl option Ar option .Op Fl Q , Fl Fl require Ar option .Op Fl r , Fl Fl request Ar address .Op Fl S , Fl Fl static Ar value .Op Fl s , Fl Fl inform Ar address Ns Op Ar /cidr .Op Fl t , Fl Fl timeout Ar seconds .Op Fl u , Fl Fl userclass Ar class .Op Fl v , Fl Fl vendor Ar code , Ar value .Op Fl W , Fl Fl whitelist Ar address Ns Op Ar /cidr .Op Fl w .Op Fl Fl waitip Op 4 | 6 .Op Fl y , Fl Fl reboot Ar seconds .Op Fl X , Fl Fl blacklist Ar address Ns Op Ar /cidr .Op Fl Z , Fl Fl denyinterfaces Ar pattern .Op Fl z , Fl Fl allowinterfaces Ar pattern .Op interface .Op ... .Nm .Fl n , Fl Fl rebind .Op interface .Nm .Fl k , Fl Fl release .Op interface .Nm .Fl U, Fl Fl dumplease .Ar interface .Nm .Fl Fl version .Nm .Fl x , Fl Fl exit .Op interface .Sh DESCRIPTION .Nm is an implementation of the DHCP client specified in .Li RFC 2131 . .Nm gets the host information .Po IP address, routes, etc .Pc from a DHCP server and configures the network .Ar interface of the machine on which it is running. .Nm then runs the configuration script which writes DNS information to .Xr resolvconf 8 , if available, otherwise directly to .Pa /etc/resolv.conf . If the hostname is currently blank, (null) or localhost, or .Va force_hostname is YES or TRUE or 1 then .Nm sets the hostname to the one supplied by the DHCP server. .Nm 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. .Pp If any interface reports a working carrier then .Nm will try and obtain a lease before forking to the background, otherwise it will fork right away. This behaviour can be modified with the .Fl b , Fl Fl background and .Fl w , Fl Fl waitip options. .Pp .Nm is also an implementation of the BOOTP client specified in .Li RFC 951 . .Pp .Nm is also an implementation of the IPv6 Router Solicitor as specified in .Li RFC 4861 and .Li RFC 6106 . .Pp .Nm is also an implementation of the IPv6 Privacy Extensions to AutoConf as specified in .Li RFC 4941 . This feature needs to be enabled in the kernel and .Nm will start using it. .Pp .Nm is also an implemenation of the DHCPv6 client as specified in .Li RFC 3315 . By default, .Nm 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. .Ss Local Link configuration If .Nm failed to obtain a lease, it probes for a valid IPv4LL address .Po aka ZeroConf, aka APIPA .Pc . Once obtained it restarts the process of looking for a DHCP server to get a proper address. .Pp When using IPv4LL, .Nm 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 .Fl L , Fl Fl noipv4ll option. .Ss Multiple interfaces If a list of interfaces are given on the command line, then .Nm only works with those interfaces, otherwise .Nm discovers available Ethernet interfaces that can be configured. When .Nm is operating on more than one interface, it is called Master mode. and this behaviour can be forced with the .Fl M , Fl Fl master option so that an individual interface can start .Nm but only one instance is running. The .Nm dhcpcd-ui project expects dhcpcd to be running this way. .Pp If a single interface is given then .Nm only works for that interface and runs as a separate instance. The .Fl w , Fl Fl waitip option is enabled in this instance to maintain compatibility with older versions. .Pp 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 .Nm 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. .Pp If an interface name is suffixed by an equal-sign, the text following the equal sign will be used instead of the interface name as the unique identifier for the DHCP lease file. Doing so allows the caller to specify different lease files for the same interface (e.g, when switching the same wireless interface between different 802.11 networks). .Ss Hooking into events .Nm runs .Pa @SCRIPT@ , or the script specified by the .Fl c , Fl Fl script option. This script runs each script found in .Pa @HOOKDIR@ in a lexical order. The default installation supplies the scripts .Pa 01-test , .Pa 10-mtu , .Pa 10-wpa_supplicant , .Pa 15-timezone , .Pa 20-resolv.conf and .Pa 30-hostname . You can disable each script by using the .Fl C , Fl Fl nohook option. See .Xr dhcpcd-run-hooks 8 for details on how these scripts work. .Nm currently ignores the exit code of the script. .Ss Fine tuning You can fine-tune the behaviour of .Nm with the following options: .Bl -tag -width indent .It Fl b , Fl Fl background Background immediately. This is useful for startup scripts which don't disable link messages for carrier status. .It Fl c , Fl Fl script Ar script Use this .Ar script instead of the default .Pa @SCRIPT@ . .It Fl D , Fl Fl duid Generate an .Li RFC 4361 compliant clientid. This requires persistent storage and not all DHCP servers work with it so it is not enabled by default. .Nm generates the DUID and stores it in .Pa @SYSCONFDIR@/dhcpcd.duid . This file should not be copied to other hosts. .It Fl d , Fl Fl debug Echo debug messages to the stderr and syslog. .It Fl E , Fl Fl lastlease If .Nm cannot obtain a lease, then try to use the last lease acquired for the interface. If the .Fl p, Fl Fl persistent option is not given then the lease is used if it hasn't expired. .It Fl e , Fl Fl env Ar value Push .Ar value to the environment for use in .Xr dhcpcd-run-hooks 8 . For example, you can force the hostname hook to always set the hostname with .Fl e .Va force_hostname=YES . .It Fl g , Fl Fl reconfigure .Nm will re-apply IP address, routing and run .Xr 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 .Nm to put things back afterwards. .Nm does not read a new configuration when this happens - you should rebind if you need that functionality. .It Fl F , Fl Fl fqdn Ar fqdn Requests that the DHCP server updates DNS using FQDN instead of just a hostname. Valid values for .Ar fqdn are disable, none, ptr and both. .Nm itself never does any DNS updates. .Nm encodes the FQDN hostname as specified in .Li RFC1035 . .It Fl f , Fl Fl config Ar file Specify a config to load instead of .Pa @SYSCONFDIR@/dhcpcd.conf . .Nm always processes the config file before any command line options. .It Fl h , Fl Fl hostname Ar hostname Sends .Ar hostname to the DHCP server so it can be registered in DNS. If .Ar hostname is an empty string then the current system hostname is sent. If .Ar hostname is a FQDN (ie, contains a .) then it will be encoded as such. .It Fl I , Fl Fl clientid Ar clientid Send the .Ar 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 .Ar clientid is an empty string then .Nm sends a default .Ar clientid of the hardware family and the hardware address. .It Fl i , Fl Fl vendorclassid Ar vendorclassid Override the DHCPv4 .Ar vendorclassid field sent. The default is dhcpcd-:::. For example .D1 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 impersonate Windows by using the MSFT vendorclassid. .It Fl j , Fl Fl logfile Ar logfile Writes to the specified .Ar logfile rather than .Xr syslog 3 . The .Ar logfile is truncated when opened and is reopened when .Nm receives the .Dv SIGUSR2 signal. .It Fl k , Fl Fl release Op Ar interface This causes an existing .Nm process running on the .Ar interface to release its lease and de-configure the .Ar interface . If no .Ar interface is specified then this applies to all interfaces. If no interfaces are left running, .Nm will exit. .It Fl l , Fl Fl leasetime Ar seconds Request a specific lease time in .Ar seconds . By default .Nm does not request any lease time and leaves it in the hands of the DHCP server. .It Fl M , Fl Fl master Start .Nm in master mode even if only one interface specified on the command line. See the Multiple Interfaces section above. .It Fl m , Fl Fl metric Ar metric Metrics are used to prefer an interface over another one, lowest wins. .Nm will supply a default metic of 200 + .Xr if_nametoindex 3 . An extra 100 will be added for wireless interfaces. .It Fl n , Fl Fl rebind Op Ar interface Notifies .Nm to reload its configuration and rebind the specified .Ar interface . If no interface is specified then this applies to all interfaces. If .Nm is not running, then it starts up as normal. This may also cause .Xr wpa_supplicant 8 to reload its configuration for each interface as well. .It Fl o , Fl Fl option Ar option Request the DHCP .Ar option variable for use in .Pa @SCRIPT@ . .It Fl p , Fl Fl persistent .Nm normally de-configures the .Ar 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. .It Fl r , Fl Fl request Op Ar address Request the .Ar address in the DHCP DISCOVER message. There is no guarantee this is the address the DHCP server will actually give. If no .Ar address is given then the first address currently assigned to the .Ar interface is used. .It Fl s , Fl Fl inform Op Ar address Ns Op Ar /cidr Behaves like .Fl r , Fl Fl 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 .Ar address in use. You should also include the optional .Ar cidr network number in case the address is not already configured on the interface. .Nm remains running and pretends it has an infinite lease. .Nm will not de-configure the interface when it exits. If .Nm fails to contact a DHCP server then it returns a failure instead of falling back on IPv4LL. .It Fl S, Fl Fl static Ar value Configures a static .Ar value . If you set .Ic ip_address then .Nm will not attempt to obtain a lease and just use the value for the address with an infinite lease time. .Pp Here is an example which configures a static address, routes and dns. .D1 dhcpcd -S ip_address=192.168.0.10/24 \e .D1 -S routers=192.168.0.1 \e .D1 -S domain_name_servers=192.168.0.1 \e .D1 eth0 .It Fl t , Fl Fl timeout Ar seconds Timeout after .Ar seconds , instead of the default 30. A setting of 0 .Ar seconds causes .Nm to wait forever to get a lease. If .Nm is working on a single interface then .Nm will exit when a timeout occurs, otherwise .Nm will fork into the background. .It Fl u , Fl Fl userclass Ar class Tags the DHCPv4 message with the userclass .Ar 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 hostname. .It Fl v , Fl Fl vendor Ar code , Ns Ar value Add an encapsulated vendor option. .Ar code should be between 1 and 254 inclusive. To add a raw vendor string, omit .Ar code but keep the comma. Examples. .Pp Set the vendor option 01 with an IP address. .D1 dhcpcd \-v 01,192.168.0.2 eth0 Set the vendor option 02 with a hex code. .D1 dhcpcd \-v 02,01:02:03:04:05 eth0 Set the vendor option 03 with an IP address as a string. .D1 dhcpcd \-v 03,\e"192.168.0.2\e" eth0 Set un-encapsulated vendor option to hello world. .D1 dhcpcd \-v ,"hello world" eth0 .It Fl Fl version Display both program version and copyright information. .Nm then exits before doing any configuration. .It Fl w Wait for an address to be assigned before forking to the background. Does not take an argument, unlike the below option. .Fl fl waitip option. .It Fl Fl waitip Op 4 | 6 Wait for an address to be assigned before forking to the background. 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, .Nm will wait for any address protocol to be assigned. It is possible to wait for more than one address protocol and .Nm will only fork to the background when all waiting conditions are satisfied. .It Fl x , Fl Fl exit Op Ar interface This will signal an existing .Nm process running on the .Ar interface to de-configure the .Ar interface and exit. If no interface is specified, then the above is applied to all interfaces. .Nm then waits until this process has exited. .It Fl y , Fl Fl reboot Ar seconds Allow .Ar reboot seconds before moving to the discover phase if we have an old lease to use. Allow .Ar reboot seconds before starting fallback states from the discover phase. IPv4LL is started when the first .Ar reboot timeout is reached. The default is 5 seconds. A setting of 0 seconds causes .Nm to skip the reboot phase and go straight into discover. This has no effect on DHCPv6 other than skipping the reboot phase. .El .Ss Restricting behaviour .Nm 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. .Bl -tag -width indent .It Fl 4 , Fl Fl ipv4only Configure IPv4 only. .It Fl 6 , Fl Fl ipv6only Configure IPv6 only. .It Fl A , Fl Fl noarp Don't request or claim the address by ARP. This also disables IPv4LL. .It Fl B , Fl Fl 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. .It Fl C , Fl Fl nohook Ar script Don't run this hook script. Matches full name, or prefixed with 2 numbers optionally ending with .Pa .sh . .Pp So to stop .Nm from touching your DNS or MTU settings you would do:- .D1 dhcpcd -C resolv.conf -C mtu eth0 .It Fl G , Fl Fl nogateway Don't set any default routes. .It Fl H , Fl Fl xidhwaddr Use the last four bytes of the hardware address as the DHCP xid instead of a randomly generated number. .It Fl J , Fl Fl 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, .Nm will set this automatically. .It Fl K , Fl Fl nolink Don't receive link messages for carrier status. You should only have to use this with buggy device drivers or running .Nm through a network manager. .It Fl L , Fl Fl noipv4ll Don't use IPv4LL (aka APIPA, aka Bonjour, aka ZeroConf). .It Fl O , Fl Fl nooption Ar 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. .It Fl Q , Fl Fl require Ar option Requires the .Ar option to be present in all DHCP messages, otherwise the message is ignored. To enforce that .Nm only responds to DHCP servers and not BOOTP servers, you can .Fl Q .Ar dhcp_message_type . .It Fl q , Fl Fl quiet Quiet .Nm on the command line, only warnings and errors will be displayed. The messages are still logged though. .It Fl T, Fl Fl test On receipt of DHCP messages just call .Pa @SCRIPT@ 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. The .Ar rapid_commit option is not sent in TEST mode so that the server does not lease an address. To test INFORM the interface needs to be configured with the desired address before starting .Nm . .It Fl U, Fl Fl dumplease Ar interface Dumps the last lease for the .Ar interface to stdout. .Ar interface could also be a path to a DHCP wire formatted file. Use the .Fl 4 or .Fl 6 flags to specify an address family. Pass a 2nd .Fl U, Fl Fl dumplease option to dump a secondary lease, such as DHCPv6 Prefix Delegation when not being mixed with another IA type. .It Fl V, Fl Fl variables Display a list of option codes, the associated variable and encoding for use in .Xr 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. .It Fl W, Fl Fl whitelist Ar address Ns Op /cidr Only accept packets from .Ar address Ns Op /cidr . .Fl X, Fl Fl blacklist is ignored if .Fl W, Fl Fl whitelist is set. .It Fl X, Fl Fl blacklist Ar address Ns Op Ar /cidr Ignore all packets from .Ar address Ns Op Ar /cidr . .It Fl Z , Fl Fl denyinterfaces Ar pattern When discovering interfaces, the interface name must not match .Ar pattern which is a space or comma separated list of patterns passed to .Xr fnmatch 3 . .It Fl z , Fl Fl allowinterfaces Ar pattern When discovering interfaces, the interface name must match .Ar pattern which is a space or comma separated list of patterns passed to .Xr fnmatch 3 . If the same interface is matched in .Fl Z , Fl Fl denyinterfaces then it is still denied. .It Fl Fl nodev Don't load any .Pa /dev management modules. .El .Sh 3RDPARTY LINK MANAGEMENT Some interfaces require configuration by 3rd parties, such as PPP or VPN. When an interface configuration in .Nm is marked as STATIC or INFORM without an address then .Nm 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 .Nm unicasts INFORM to the destination, otherwise it defaults to STATIC. .Sh NOTES .Nm 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. .Pp If restricting .Nm to a single interface and optionally address family via the command-line then all futher calls to .Nm to rebind, reconfigure or exit need to include the same restrictive flags so that .Nm knows which process to signal. .Sh FILES .Bl -ohang .It Pa @SYSCONFDIR@/dhcpcd.conf Configuration file for dhcpcd. If you always use the same options, put them here. .It Pa @SYSCONFDIR@/dhcpcd.duid Text file that holds the DUID used to identify the host. .It Pa @SYSCONFDIR@/dhcpcd.secret Text file that holds a secret key known only to the host. .It Pa @SCRIPT@ Bourne shell script that is run to configure or de-configure an interface. .It Pa @LIBDIR@/dhcpcd/dev .Pa /dev management modules. .It Pa @HOOKDIR@ A directory containing bourne shell scripts that are run by the above script. Each script can be disabled by using the .Fl C , Fl Fl nohook option described above. .It Pa @DBDIR@/dhcpcd\- Ns Ar interface Ns Ar -ssid Ns .lease 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. .It Pa @DBDIR@/dhcpcd\- Ns Ar interface Ns Ar -ssid Ns .lease6 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. .It Pa @DBDIR@/dhcpcd-rdm.monotonic Stores the monotonic counter used in the .Ar replay field in Authentication Options. .It Pa @RUNDIR@/dhcpcd.pid Stores the PID of .Nm running on all interfaces. .It Pa @RUNDIR@/dhcpcd\- Ns Ar interface Ns .pid Stores the PID of .Nm running on the .Ar interface . .It Pa @RUNDIR@/dhcpcd.sock Control socket to the master daemon. .It Pa @RUNDIR@/dhcpcd.unpriv.sock Unpriviledged socket to the master daemon, only allows state retrieval. Control socket to the master daemon. .It Pa @RUNDIR@/dhcpcd\- Ns Ar interface Ns .sock Control socket to per interface daemon. .El .Sh SEE ALSO .Xr fnmatch 3 , .Xr if_nametoindex 3 , .Xr dhcpcd.conf 5 , .Xr resolv.conf 5 , .Xr dhcpcd-run-hooks 8 , .Xr resolvconf 8 .Sh STANDARDS 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\ 4941, RFC\ 5227, RFC\ 5942, RFC\ 5969, RFC\ 6106, RFC\ 6334, RFC\ 6603, RFC\ 6704, RFC\ 7217. .Sh AUTHORS .An Roy Marples Aq Mt roy@marples.name .Sh BUGS Please report them to .Lk http://roy.marples.name/projects/dhcpcd