cat FILE | resolvconf -a IFACE.PROG
resolvconf -d IFACE.PROG
resolvconf --enable-updates | --disable-updates | --updates-are-enabled
| --create-runtime-directories | --wipe-runtime-directories
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-
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 126.96.36.199 188.8.131.52
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
iface eth0 inet static
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
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.
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.
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).
Set the flag indicating that resolvconf should run update
scripts when invoked in the future with -a, -d or -u. If a
Delete everything in the directories where resolver information
records and other run-time files are stored.
The following variables can be set in the default-override file
/etc/default/resolvconf. If the file does not exist you will have to
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".
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
See the ENVIRONMENT VARIABLES section.
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-
Determines the order in which nameserver information records are
processed. See interface-order(5).
File containing basic resolver information. The lines in this
file are included in the resolver configuration file even when
no interfaces are configured.
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
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
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.
Currently resolvconf does not check the sanity of the information pro-
vided to it.
Written by Thomas Hood <firstname.lastname@example.org>.
Copyright (C) 2004, 2011 Thomas Hood
This is free software; see the source for copying conditions.
interface-order(5), resolv.conf(5), resolver(3).
resolvconf 6 Dec 2011 RESOLVCONF(8)
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