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.Dd Mar 05, 2008
.Dt RESOLVCONF 8 SMM
.Sh NAME
.Nm resolvconf
.Nd a framework for managing multiple DNS configurations
.Sh SYNOPSIS
.Nm
.Fl a Ar interface No < Ns Pa file
.Nm
.Op Fl f
.Fl d Ar interface
.Nm
.Fl il Ar pattern
.Nm
.Fl u
.Sh DESCRIPTION
.Nm
manages
.Xr resolv.conf 5
files from multiple sources, such as DHCP and VPN clients.
Traditionally, the host runs just one client and that updates
.Pa /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
.Pa /etc/resolv.conf .
.Pp
.Nm
solves this by letting the daemon send their
.Xr resolv.conf 5
file to
.Nm
via
.Xr stdin 3
with the argument
.Fl a Ar interface
instead of the filesystem.
.Nm
then updates
.Pa /etc/resolv.conf
as it thinks best.
When a local resolver other than libc is installed, such as
.Xr dnsmasq 8
or
.Xr named 8
then
.Nm
will configure
.Pa /etc/resolv.conf
to use that and supply files that the resolver should be configured to include.
This allows
.Nm
to configure the local resolver such that
.Pa resolv.conf
files specifiying a domain only query the listed nameservers when resolving
for that domain. Otherwise the nameservers are treated as global nameservers.
This in turn means, that you can trivially configure nameservers for say
VPN domains. Example:-
.Bd -literal -offset indent
# resolv.conf from bge0
search foo.com
nameserver 1.2.3.4

# resolv.conf from tap0
domain bar.org
nameserver 5.6.7.8
.Ed
.Pp
In this instance, nameserver 5.6.7.8 will only handle requests for bar.org
and nameserver 1.2.3.4 will handle everything else.
.Pp
When an interface goes down, it should then call
.Nm
with
.Fl d Ar interface
arguments to delete the
.Pa resolv.conf
file for the
.Ar interface .
.Pp
Here are some more options that
.Nm
has:-
.Bl -tag -width indent
.It Fl f
Ignore non existant interfaces. Only really useful for deleting interfaces.
.It Fl i Ar pattern
List the interfaces, optionally matching
.Ar pattern ,
we have
.Pa resolv.conf
files for.
.It Fl l Ar pattern
List the
.Pa resolv.conf
files we have. If
.Ar pattern
is specified then we list the files for the interfaces that match it.
.It Fl u
Force
.Nm
to update all it's helpers.
.El
.Pp
.Nm
also has some options designed to be used by it's helpers:-
.Bl -tag -width indent
.It Fl s Ar service Ar command ...
Try and send the
.Ar command
to the system
.Ar service .
Normally this is something like
.Ar resolvconf -s named restart .
We have this command, so the helpers don't have to know too much about the
operating system on the host.
.It Fl v
Echo variables NEWDOMAIN, NEWSEARCH and NEWNS so that the helper can configure
the resolver easily.
.El
.Sh FILES
.Bl -ohang
.It Pa @VARBASE@/run/resolvconf
Directory that holds the data for
.Nm .
You could symlink
.Pa /etc/resolv.conf
to
.Pa @VARBASE@/run/resolvconf/resolv.conf
to support a read only
.Pa /etc .
.It Pa @SYSCONFDIR@/update.d
Directory of the helper scripts which are run every time
.Nm
adds, deletes or updates.
.It Pa @SYSCONFDIR@/update-libc.d
Directory of helper scripts which are run after the libc helper script is run.
.It Pa @SYSCONFDIR@/interface-order
Determines the order in which nameserver information records are processed
by resolvconf -l.
.It Pa @SYSCONFDIR@/resolv.conf.d/base
Contains basic resolver information which is included in
.Pa /etc/resolv.conf
even when no interfaces are configured.
.It Pa @SYSCONFDIR@/resolv.conf.d/head
File to be prepended to
.Pa /etc/resolv.conf .
Normally this is just a comment line.
.It Pa @SYSCONFDIR@/resolv.conf.d/tail
File to be appended to
.Pa /etc/resolv.conf .
.El
.Sh HISTORY
This implementation of
.Nm
is called openresolv and is fully command line compatible with Debians
resolvconf, as written by Thomas Hood, on which openresolv is based.
openresolv also shares a similar directory structure with the Debian version,
but the included helpers are not compatible.
.Pp
The Debian version only works with bash and other GNU userland tools, whereas
openresolv works with a POSIX shell and userland tools.
.Sh BUGS
.Nm
does not validate any of the files given to it.
.Pp
When running a local resolver other than libc, you will need to configure it
to include files that
.Nm
will generate. You should consult the comment section in the helper script
for your resolver found in @SYSCONFDIR@/update.d for instructions
on this.
.Sh SEE ALSO
.Xr dnsmasq 8 ,
.Xr named 8 ,
.Xr resolv.conf 5 ,
.Xr resolver 3 ,
.Xr stdin 3
.Sh AUTHORS
.An "Roy Marples" Aq roy@marples.name
.Sh BUGS
Please report them to http://bugs.marples.name