NAME¶
resolvconf —
a framework for managing
multiple DNS configurations
SYNOPSIS¶
| resolvconf |
[-m
metric]
[-p] -a
interface
<file |
| resolvconf |
[-f] -d
interface |
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 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
/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 it's
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 it's
subscribers:-
- -v
- Echo variables DOMAINS, SEARCH and NAMESERVERS so that the
subscriber can configure the resolver easily.
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/resolvconf.conf
- Configuration file for resolvconf.
- /lib/resolvconf
- Directory of subscribers which are run every time
resolvconf adds, deletes or updates.
- /lib/resolvconf/libc.d
- Directory of subscribers which are run after the libc
subscriber is run.
- /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.
