NAME

resolvconf — a framework for managing multiple DNS configurations

SYNOPSIS

resolvconf

-I

resolvconf

[-m metric] [-p] -a interface <file

resolvconf

[-f] -d interface

resolvconf

-il pattern

resolvconf

-u

DESCRIPTION

resolvconf manages resolv.conf(5) files from multiple sources, such as DHCP and VPN clients. Traditionally, the host runs just one client and that updates /etc/resolv.conf. More modern systems frequently have wired and wireless interfaces and there is no guarantee both are on the same network. With the advent of VPN and other types of networking daemons, many things now contend for the contents of /etc/resolv.conf.

resolvconf solves this by letting the daemon send their resolv.conf(5) file to resolvconf via stdin(3) with the argument -a interface instead of the filesystem. resolvconf then updates /etc/resolv.conf as it thinks best. When a local resolver other than libc is installed, such as dnsmasq(8) or named(8), then resolvconf will supply files that the resolver should be configured to include.

resolvconf assumes it has a job to do. In some situations resolvconf needs to act as a deterrent to writing to /etc/resolv.conf. Where this file cannot be made immutable or you just need to toggle this behaviour, resolvconf can be disabled by adding resolvconf=NO to resolvconf.conf(5).

resolvconf can mark an interfaces resolv.conf as private. This means that the name servers listed in that resolv.conf are only used for queries against the domain/search listed in the same file. This only works when a local resolver other than libc is installed. See resolvconf.conf(5) for how to configure resolvconf to use a local name server.

When an interface goes down, it should then call resolvconf with -d interface arguments to delete the resolv.conf file for the interface.

Here are some more options that resolvconf has:-

-I

Initialise the state directory /var/run/resolvconf. This only needs to be called if the initial system boot sequence does not automatically clean it out; for example the state directory is moved somewhere other than /var/run. If used, it should only be called once as early in the system boot sequence as possible and before resolvconf is used to add interfaces.

-f

Ignore non existant interfaces. Only really useful for deleting interfaces.

-i pattern

List the interfaces, optionally matching pattern, we have resolv.conf files for.

-l pattern

List the resolv.conf files we have. If pattern is specified then we list the files for the interfaces that match it.

-m metric

Set the metric of the interface when adding it, default of 0. Lower metrics take precedence. This affects the default order of interfaces when listed.

-p

Marks the interface resolv.conf as private.

-u

Force resolvconf to update all its subscribers. resolvconf does not update the subscribers when adding a resolv.conf that matches what it already has for that interface.

resolvconf also has some options designed to be used by its subscribers:-

-v

Echo variables DOMAINS, SEARCH and NAMESERVERS so that the subscriber can configure the resolver easily.

-V

Same as -v except that only the information configured in resolvconf.conf(5) is set.

INTERFACE ORDERING

For resolvconf to work effectively, it has to process the resolv.confs for the interfaces in the correct order. resolvconf first processes interfaces from the interface_order list, then interfaces without a metic and that match the dynamic_order list, then interfaces with a metric in order and finally the rest in the operating systems lexical order. See resolvconf.conf(5) for details on these lists.

IMPLEMENTATION NOTES

If a subscriber has the executable bit then it is executed otherwise it is assumed to be a shell script and sourced into the current environment in a subshell. This is done so that subscribers can remain fast, but are also not limited to the shell language.

Portable subscribers should not use anything outside of /bin and /sbin because /usr and others may not be available when booting. Also, it would be unwise to assume any shell specific features.

ENVIRONMENT

IF_METRIC

If the -m option is not present then we use IF_METRIC for the metric.

IF_PRIVATE

Marks the interface resolv.conf as private.

FILES

/etc/resolv.conf.bak

Backup file of the original resolv.conf.

/etc/resolvconf.conf

Configuration file for resolvconf.

/libexec/resolvconf

Directory of subscribers which are run every time resolvconf adds, deletes or updates.

/libexec/resolvconf/libc.d

Directory of subscribers which are run after the libc subscriber is run.

/var/run/resolvconf

State directory for resolvconf.

HISTORY

This implementation of resolvconf is called openresolv and is fully command line compatible with Debian's resolvconf, as written by Thomas Hood.

SEE ALSO

resolv.conf(5), resolvconf.conf(5), resolver(3), stdin(3)

AUTHORS

Roy Marples <roy@marples.name>

BUGS

Please report them to http://roy.marples.name/projects/openresolv

resolvconf does not validate any of the files given to it.

When running a local resolver other than libc, you will need to configure it to include files that resolvconf will generate. You should consult resolvconf.conf(5) for instructions on how to configure your resolver.