resolvconf


SYNOPSIS
       cat FILE | resolvconf -a IFACE.PROG

       resolvconf -d IFACE.PROG

       resolvconf -u

       resolvconf --enable-updates | --disable-updates | --updates-are-enabled
       | --create-runtime-directories | --wipe-runtime-directories

DESCRIPTION
       Overwrite  (-a)  or  delete  (-d)  the  nameserver  information  record
       IFACE.PROG.   Also  run the update scripts in /etc/resolvconf/update.d/
       if the nameserver information has changed and updating is enabled.

       With -u, just run the update scripts if updating is enabled.

       With -a, -d or -u schedule a delayed update if  updating  is  not  cur-
       rently enabled.

PUBLICATION
       Normally  resolvconf  is  run  only by hook scripts attached to network
       interface configurers such as pppd(8) (for  ppp  interfaces),  to  DHCP
       clients  such  as dhclient(8), to ifup(8) and ifdown, and to DNS caches
       such as dnsmasq(8) (for the loopback interface).   These  hook  scripts
       furnish  resolvconf  with  information about nameservers.  For example,
       dhclient receives one or more nameserver addresses during its  negotia-
       tion  with  the  DHCP server; its hook script /etc/dhcp/dhclient-enter-
       hooks.d/resolvconf pushes this information to resolvconf.

       The ifup(8) program can be used to configure network interfaces accord-
       ing to settings in /etc/network/interfaces(5).  To make ifup push name-
       server information to resolvconf when it configures an  interface,  add
       dns- lines to the relevant iface stanza in /etc/network/interfaces.  To
       add nameserver addresses add a line beginning with dns-nameservers.

           dns-nameservers 11.22.33.44 55.66.77.88

       Note that one or more addresses can be given, and note the `s'  at  the
       end of the option name.  (Contrast with the resolv.conf(5) option name-
       server.)  For each other valid resolv.conf(5) configuration option, you
       can  include,  in  the stanza, one line beginning with that option name
       with a dns- prefix.  The resulting stanza might look like the following
       example.

           iface eth0 inet static
               address 192.168.3.3
               netmask 255.255.255.0
               gateway 192.168.3.1
               dns-nameservers 192.168.3.45 192.168.8.10
               dns-search foo.org bar.com

       See the resolvconf package's README file for more detailed information.
       scribe to the notification service so that they know whither to forward
       queries.

       The most important piece of software that subscribes to  the  notifica-
       tion  service  is  the  set of functions that make up the GNU C Library
       resolver(3).   When  nameserver  information  is  updated,  the  script
       /etc/resolvconf/update.d/libc  writes a new resolver configuration file
       to  /run/resolvconf/resolv.conf  and   then   runs   the   scripts   in
       /etc/resolvconf/update-libc.d/.   To  make the resolver use the dynami-
       cally generated resolver configuration file  the  administrator  should
       ensure  that  /etc/resolv.conf  is  a  symbolic  link  to  /run/resolv-
       conf/resolv.conf.  This link is never modified  by  resolvconf(8).   If
       you find that /etc/resolv.conf is not being updated, check to make sure
       that the link is intact.

       The GNU C Library resolver library  isn't  the  only  resolver  library
       available.   However,  any resolver library that reads /etc/resolv.conf
       (and most of them do, in order to be compatible with the GNU C  Library
       resolver) should work with resolvconf(8).

       Subscribers that need to know only when the resolver configuration file
       has changed should install a script  in  /etc/resolvconf/update-libc.d/
       rather  than  in /etc/resolvconf/update.d/.  This is important for syn-
       chronization  purposes:  scripts  in  update-libc.d/  are   run   after
       resolv.conf  has  been  updated;  the  same  is not necessarily true of
       scripts in update.d/.  Examples of packages that  do  this  are  fetch-
       mail(1) and squid(8).

       Client  hook scripts will find the files containing nameserver informa-
       tion in the current directory.

OPTIONS
       -a IFACE.PROG
              Add or overwrite the record IFACE.PROG.   When  this  option  is
              used the information must be provided to resolvconf on its stan-
              dard input in the format of the resolv.conf(5) file.  Each  line
              in the file must be terminated by a newline.

       -d IFACE.PROG
              Delete the record IFACE.PROG.

       The  string IFACE.PROG name may not contain spaces, slashes, an initial
       dot, an initial hyphen or  an  initial  tilde.   It  is  conventionally
       formed from IFACE, the name of the interface involved, a dot, and PROG,
       the name of the interface configuration program, e.g., `eth0.dhclient'.

       Following the addition or  deletion  of  the  record,  run  the  update
       scripts (if updating is enabled).

       -u     Just run the update scripts (if updating is enabled).

       --enable-updates
              Set  the  flag  indicating  that  resolvconf  should  run update
              scripts when invoked in the future with -a,  -d  or  -u.   If  a

       --wipe-runtime-directories
              Delete everything in the directories where resolver  information
              records and other run-time files are stored.

ENVIRONMENT VARIABLES
       The  following  variables  can  be  set  in  the  default-override file
       /etc/default/resolvconf.  If the file does not exist you will  have  to
       create it.

       REPORT_ABSENT_SYMLINK
              If  set  to  "yes"  then  resolvconf  will  print a message when
              /etc/resolv.conf  is  not  a  symbolic  link  to   the   resolv-
              conf(8)-generated  resolv.conf file.  Set to "no" to prevent the
              printing of this message.  The default is "yes".

       TRUNCATE_NAMESERVER_LIST_AFTER_LOOPBACK_ADDRESS
              If set to "yes" then the update.d/libc script  will  include  no
              more  nameserver addresses after the first loopback address.  In
              IPv4 a loopback address is an address that  starts  with  "127."
              This  is  usually  the  preferable behavior if the nameserver at
              127.* is a local caching nameserver since it  inhibits  unneces-
              sary  changes  to  resolv.conf.  When an interface is brought up
              the local caching nameserver is informed by resolvconf(8) of any
              new nameserver addresses and the additional name service is made
              available to applications that make use of the resolver and  the
              local  caching  nameserver;  the  applications themselves do not
              need to be notified of the change.  A disadvantage of this  mode
              of  operation is that applications have no secondary or tertiary
              nameserver address to fall back  on  should  the  local  caching
              nameserver  crash.   Insofar  as a local nameserver crash can be
              regarded as an unlikely event, this is a relatively minor disad-
              vantage.   Set  to "no" to disable this truncation feature.  The
              default is "yes".  A deprecated synonym  for  this  variable  is
              TRUNCATE_NAMESERVER_LIST_AFTER_127.

FILES
       /etc/default/resolvconf
              See the ENVIRONMENT VARIABLES section.

       /run/resolvconf
              This is the location where nameserver information is stored.  It
              will be created if resolvconf is called with  the  --create-run-
              time-directories  option.   Clients  should not make any assump-
              tions about the hierarchy that is constructed under this  direc-
              tory.

       /etc/resolvconf/interface-order
              Determines the order in which nameserver information records are
              processed.  See interface-order(5).

       /etc/resolvconf/resolv.conf.d/base
              File containing basic resolver information.  The lines  in  this
              file  are  included in the resolver configuration file even when
              no interfaces are configured.

       /etc/resolvconf/resolv.conf.d/original
              Copy of the /etc/resolv.conf file before the resolvconf  package
              was  installed.   This  file has no effect on the functioning of
              resolvconf; it is  retained  so  that  /etc/resolv.conf  can  be
              restored  to  its  original  state  if the resolvconf package if
              removed.

              Note also that a copy of this file is included in  the  database
              until  the  first  reboot  after  installation of the resolvconf
              package; this ensures that nameservers reachable before  instal-
              lation  of  resolvconf are still reachable after installation of
              resolvconf even though at that point not all suppliers of  name-
              server  information  may  have  supplied  their  information  to
              resolvconf(8).

              Note also that the administrator can choose to create a symbolic
              link  in /etc/resolvconf/resolv.conf.d/ from tail to original so
              that the contents of the latter are always added to the  end  of
              the dynamically generated resolv.conf.


BUGS
       Currently  resolvconf does not check the sanity of the information pro-
       vided to it.

AUTHOR
       Written by Thomas Hood <jdthood@gmail.com>.

COPYRIGHT
       Copyright (C) 2004, 2011 Thomas Hood
       This is free software; see the source for copying conditions.

SEE ALSO
       interface-order(5), resolv.conf(5), resolver(3).



resolvconf                        6 Dec 2011                     RESOLVCONF(8)
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