212 lines
6.8 KiB
Groff
212 lines
6.8 KiB
Groff
.\" Copyright (c) 1986, 1991, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" @(#)resolver.5 8.1 (Berkeley) 6/5/93
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd November 11, 1993
|
|
.Dt RESOLVER 5
|
|
.Os
|
|
.Sh NAME
|
|
.Nm resolver
|
|
.Nd resolver configuration file
|
|
.Sh SYNOPSIS
|
|
.Nm resolv.conf
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Xr resolver 3
|
|
is a set of routines in the C library
|
|
which provide access to the Internet Domain Name System.
|
|
The resolver configuration file contains information that is read
|
|
by the resolver routines the first time they are invoked by a process.
|
|
The file is designed to be human readable and contains a list of
|
|
keywords with values that provide various types of resolver information.
|
|
.Pp
|
|
On a normally configured system this file should not be necessary.
|
|
The only name server to be queried will be on the local machine,
|
|
the domain name is determined from the host name,
|
|
and the domain search path is constructed from the domain name.
|
|
.Pp
|
|
The different configuration options are:
|
|
.Bl -tag -width nameserver
|
|
.It Sy nameserver
|
|
Internet address (in dot notation) of a name server
|
|
that the resolver should query.
|
|
Up to
|
|
.Dv MAXNS
|
|
(currently 3) name servers may be listed,
|
|
one per keyword.
|
|
If there are multiple servers,
|
|
the resolver library queries them in the order listed.
|
|
If no
|
|
.Sy nameserver
|
|
entries are present,
|
|
the default is to use the name server on the local machine.
|
|
(The algorithm used is to try a name server, and if the query times out,
|
|
try the next, until out of name servers,
|
|
then repeat trying all the name servers
|
|
until a maximum number of retries are made).
|
|
.It Sy domain
|
|
Local domain name.
|
|
Most queries for names within this domain can use short names
|
|
relative to the local domain.
|
|
If no
|
|
.Sy domain
|
|
entry is present, the domain is determined
|
|
from the local host name returned by
|
|
.Xr gethostname 3 ;
|
|
the domain part is taken to be everything after the first `.'.
|
|
Finally, if the host name does not contain a domain part, the root
|
|
domain is assumed.
|
|
.It Sy search
|
|
Search list for host-name lookup.
|
|
The search list is normally determined from the local domain name;
|
|
by default, it contains only the local domain name.
|
|
This may be changed by listing the desired domain search path
|
|
following the
|
|
.Sy search
|
|
keyword with spaces or tabs separating
|
|
the names.
|
|
Most resolver queries will be attempted using each component
|
|
of the search path in turn until a match is found.
|
|
Note that this process may be slow and will generate a lot of network
|
|
traffic if the servers for the listed domains are not local,
|
|
and that queries will time out if no server is available
|
|
for one of the domains.
|
|
.Pp
|
|
The search list is currently limited to six domains
|
|
with a total of 256 characters.
|
|
.It Sy sortlist
|
|
Sortlist allows addresses returned by gethostbyname to be sorted.
|
|
A sortlist is specified by IP address netmask pairs.
|
|
The netmask is
|
|
optional and defaults to the natural netmask of the net.
|
|
The IP address
|
|
and optional network pairs are separated by slashes.
|
|
Up to 10 pairs may
|
|
be specified.
|
|
.Pp
|
|
e.g. sortlist 130.155.160.0/255.255.240.0 130.155.0.0
|
|
.It Sy options
|
|
Options allows certain internal resolver variables to be modified.
|
|
The syntax is
|
|
.Pp
|
|
\fBoptions\fP \fIoption\fP \fI...\fP
|
|
.Pp
|
|
where
|
|
.Sy option
|
|
is one of the following:
|
|
.Pp
|
|
.Bl -tag -width no_tld_query
|
|
.It Sy debug
|
|
sets
|
|
.Dv RES_DEBUG
|
|
in _res.options.
|
|
.It Sy ndots: Ns Ar n
|
|
sets a threshold for the number of dots which must appear in a name given to
|
|
.Fn res_query
|
|
(see
|
|
.Xr resolver 3 )
|
|
before an
|
|
.Em initial absolute query
|
|
will be made.
|
|
The default for
|
|
.Em n
|
|
is
|
|
.Dq 1 ,
|
|
meaning that if there are any dots in a name, the name
|
|
will be tried first as an absolute name before any
|
|
.Em search list
|
|
elements are appended to it.
|
|
.It Sy timeout: Ns Ar n
|
|
sets the amount of time the resolver will wait for a response from a remote
|
|
name server before retrying the query via a different name server. Measured in
|
|
seconds, the default is
|
|
.Dv RES_TIMEOUT
|
|
(see
|
|
.Pa <resolv.h> ) .
|
|
.It Sy attempts: Ns Ar n
|
|
sets the number of times the resolver will send a query to its name servers
|
|
before giving up and returning an error to the calling application. The
|
|
default is
|
|
.Dv RES_DFLRETRY
|
|
(see
|
|
.Pa <resolv.h> ) .
|
|
.It Sy no_tld_query
|
|
tells the resolver not to attempt to resolve a top level domain name, that
|
|
is, a name that contains no dots. Use of this option doesn't prevent
|
|
the resolver from obeying the standard
|
|
.Sy domain
|
|
and
|
|
.Sy search
|
|
rules with the given name.
|
|
.El
|
|
.Pp
|
|
Options may also be specified as a space or tab separated list using the
|
|
.Dv RES_OPTIONS
|
|
environment variable.
|
|
.El
|
|
.Pp
|
|
The
|
|
.Sy domain
|
|
and
|
|
.Sy search
|
|
keywords are mutually exclusive.
|
|
If more than one instance of these keywords is present,
|
|
the last instance will override.
|
|
.Pp
|
|
The keyword and value must appear on a single line, and the keyword
|
|
(e.g.\&
|
|
.Sy nameserver )
|
|
must start the line. The value follows
|
|
the keyword, separated by white space.
|
|
.Sh FILES
|
|
.Bl -tag -width /etc/resolv.conf -compact
|
|
.It Pa /etc/resolv.conf
|
|
The file
|
|
.Nm resolv.conf
|
|
resides in
|
|
.Pa /etc .
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr gethostbyname 3 ,
|
|
.Xr resolver 3 ,
|
|
.Xr hostname 7 ,
|
|
.Xr named 8
|
|
.Rs
|
|
.%T "Name Server Operations Guide for BIND"
|
|
.Re
|
|
.Sh HISTORY
|
|
The
|
|
.Nm resolv.conf
|
|
file format appeared in
|
|
.Bx 4.3 .
|