+++ /dev/null
-.\" Copyright (c) 1986 The Regents of the University of California.
-.\" All rights reserved.
-.\"
-.\" %%%LICENSE_START(PERMISSIVE_MISC)
-.\" Redistribution and use in source and binary forms are permitted
-.\" provided that the above copyright notice and this paragraph are
-.\" duplicated in all such forms and that any documentation,
-.\" advertising materials, and other materials related to such
-.\" distribution and use acknowledge that the software was developed
-.\" by the University of California, Berkeley. The name of the
-.\" University may not be used to endorse or promote products derived
-.\" from this software without specific prior written permission.
-.\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
-.\" IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
-.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
-.\" %%%LICENSE_END
-.\"
-.\" @(#)resolver.5 5.9 (Berkeley) 12/14/89
-.\" $Id: resolver.5,v 8.6 1999/05/21 00:01:02 vixie Exp $
-.\"
-.\" Added ndots remark by Bernhard R. Link - debian bug #182886
-.\"
-.TH RESOLV.CONF 5 2014-12-31 "" "Linux Programmer's Manual"
-.UC 4
-.SH NAME
-resolv.conf \- resolver configuration file
-.SH SYNOPSIS
-.B /etc/resolv.conf
-.SH DESCRIPTION
-The
-.I resolver
-is a set of routines in the C library
-that provide access to the Internet Domain Name System (DNS).
-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.
-The configuration file is considered a trusted source of DNS information
-(e.g., DNSSEC AD-bit information will be returned unmodified from this
-source).
-.LP
-If this file does not exist,
-only the name server on the local machine will be queried;
-the domain name is determined from the hostname
-and the domain search path is constructed from the domain name.
-.LP
-The different configuration options are:
-.TP
-\fBnameserver\fP Name server IP address
-Internet address of a name server that the resolver should query,
-either an IPv4 address (in dot notation),
-or an IPv6 address in colon (and possibly dot) notation as per RFC 2373.
-Up to
-.B MAXNS
-(currently 3, see \fI<resolv.h>\fP) name servers may be listed,
-one per keyword.
-If there are multiple servers,
-the resolver library queries them in the order listed.
-If no \fBnameserver\fP 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.)
-.TP
-\fBdomain\fP Local domain name.
-Most queries for names within this domain can use short names
-relative to the local domain.
-If set to \(aq.\(aq, the root domain is considered.
-If no \fBdomain\fP entry is present, the domain is determined
-from the local hostname returned by
-.BR gethostname (2);
-the domain part is taken to be everything after the first \(aq.\(aq.
-Finally, if the hostname does not contain a domain part, the root
-domain is assumed.
-.TP
-\fBsearch\fP 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 \fIsearch\fP keyword with spaces or tabs separating
-the names.
-Resolver queries having fewer than
-.I ndots
-dots (default is 1) in them will be attempted using each component
-of the search path in turn until a match is found.
-For environments with multiple subdomains please read
-.BI "options ndots:" n
-below to avoid man-in-the-middle attacks and unnecessary
-traffic for the root-dns-servers.
-.\" When having a resolv.conv with a line
-.\" search subdomain.domain.tld domain.tld
-.\" and doing a hostlookup, for example by
-.\" ping host.anothersubdomain
-.\" it sends dns-requests for
-.\" host.anothersubdomain.
-.\" host.anothersubdomain.subdomain.domain.tld.
-.\" host.anothersubdomain.domain.tld.
-.\" thus not only causing unnecessary traffic for the root-dns-servers
-.\" but broadcasting information to the outside and making man-in-the-middle
-.\" attacks possible.
-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.
-.IP
-The search list is currently limited to six domains
-with a total of 256 characters.
-.TP
-\fBsortlist\fP
-This option allows addresses returned by
-.BR gethostbyname (3)
-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.
-Here is an example:
-
-.in +4n
-sortlist 130.155.160.0/255.255.240.0 130.155.0.0
-.in
-.br
-.TP
-\fBoptions\fP
-Options allows certain internal resolver variables to be modified.
-The syntax is
-.RS
-.IP
-\fBoptions\fP \fIoption\fP \fI...\fP
-.LP
-where \fIoption\fP is one of the following:
-.TP
-\fBdebug\fP
-.\" Since glibc 2.2?
-sets
-.BR RES_DEBUG
-in
-.IR _res.options
-(effective only if glibc was built with debug support; see
-.BR resolver (3)).
-.TP
-.BI ndots: n
-.\" Since glibc 2.2
-sets a threshold for the number of dots which
-must appear in a name given to
-.BR res_query (3)
-(see
-.BR resolver (3))
-before an \fIinitial absolute query\fP will be made.
-The default for
-\fIn\fP is 1, meaning that if there are any dots in a name, the name
-will be tried first as an absolute name before any \fIsearch list\fP
-elements are appended to it.
-The value for this option is silently capped to 15.
-.TP
-.BI timeout: n
-.\" Since glibc 2.2
-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
-.BR RES_TIMEOUT
-(currently 5, see \fI<resolv.h>\fP).
-The value for this option is silently capped to 30.
-.TP
-.BI attempts: 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
-.BR RES_DFLRETRY
-(currently 2, see \fI<resolv.h>\fP).
-The value for this option is silently capped to 5.
-.TP
-.B rotate
-.\" Since glibc 2.2
-sets
-.BR RES_ROTATE
-in
-.IR _res.options ,
-which causes round-robin selection of name servers from among those listed.
-This has the effect of spreading the query load among all listed servers,
-rather than having all clients try the first listed server first every time.
-.TP
-.B no-check-names
-.\" since glibc 2.2
-sets
-.BR RES_NOCHECKNAME
-in
-.IR _res.options ,
-which disables the modern BIND checking of incoming hostnames and
-mail names for invalid characters such as underscore (_), non-ASCII,
-or control characters.
-.TP
-.B inet6
-.\" Since glibc 2.2
-sets
-.BR RES_USE_INET6
-in
-.IR _res.options .
-This has the effect of trying a AAAA query before an A query inside the
-.BR gethostbyname (3)
-function, and of mapping IPv4 responses in IPv6 "tunneled form"
-if no AAAA records are found but an A record set exists.
-.TP
-.BR ip6-bytestring " (since glibc 2.3.4)"
-sets
-.BR RES_USE_BSTRING
-in
-.IR _res.options .
-This causes reverse IPv6 lookups to be made using the bit-label format
-described in RFC\ 2673;
-if this option is not set, then nibble format is used.
-.TP
-.BR ip6-dotint / no-ip6-dotint " (since glibc 2.3.4)"
-Clear/set
-.BR RES_NOIP6DOTINT
-in
-.IR _res.options .
-When this option is clear
-.RB ( ip6-dotint ),
-reverse IPv6 lookups are made in the (deprecated)
-.I ip6.int
-zone;
-when this option is set
-.RB ( no-ip6-dotint ),
-reverse IPv6 lookups are made in the
-.I ip6.arpa
-zone by default.
-This option is set by default.
-.TP
-.BR edns0 " (since glibc 2.6)"
-sets
-.BR RES_USE_EDNSO
-in
-.IR _res.options .
-This enables support for the DNS extensions described in RFC\ 2671.
-.TP
-.BR single-request " (since glibc 2.10)"
-sets
-.BR RES_SNGLKUP
-in
-.IR _res.options .
-By default, glibc performs IPv4 and IPv6 lookups in parallel since
-version 2.9.
-Some appliance DNS servers
-cannot handle these queries properly and make the requests time out.
-This option disables the behavior and makes glibc perform the IPv6
-and IPv4 requests sequentially (at the cost of some slowdown of the
-resolving process).
-.TP
-.BR single-request-reopen " (since glibc 2.9)"
-The resolver uses the same socket for the A and AAAA requests.
-Some hardware mistakenly sends back only one reply.
-When that happens the client system will sit and wait for the second reply.
-Turning this option on changes this behavior
-so that if two requests from the same port are not handled correctly it will
-close the socket and open a new one before sending the second request.
-.TP
-.BR no-tld-query " (since glibc 2.14)"
-sets RES_NOTLDQUERY in
-.IR _res.options .
-This option causes
-.BR res_nsearch ()
-to not attempt to resolve an unqualified name
-as if it were a top level domain (TLD).
-This option can cause problems if the site has ``localhost'' as a TLD
-rather than having localhost on one or more elements of the search list.
-This option has no effect if neither RES_DEFNAMES or RES_DNSRCH is set.
-.RE
-.LP
-The \fIdomain\fP and \fIsearch\fP keywords are mutually exclusive.
-If more than one instance of these keywords is present,
-the last instance wins.
-.LP
-The \fIsearch\fP keyword of a system's \fIresolv.conf\fP file can be
-overridden on a per-process basis by setting the environment variable
-.B LOCALDOMAIN
-to a space-separated list of search domains.
-.LP
-The \fIoptions\fP keyword of a system's \fIresolv.conf\fP file can be
-amended on a per-process basis by setting the environment variable
-.B RES_OPTIONS
-to a space-separated list of resolver options
-as explained above under \fBoptions\fP.
-.LP
-The keyword and value must appear on a single line, and the keyword
-(e.g., \fBnameserver\fP) must start the line.
-The value follows the keyword, separated by white space.
-
-Lines that contain a semicolon (;) or hash character (#)
-in the first column are treated as comments.
-.SH FILES
-.IR /etc/resolv.conf ,
-.I <resolv.h>
-.SH SEE ALSO
-.BR gethostbyname (3),
-.BR resolver (3),
-.BR hostname (7),
-.BR named (8)
-.br
-Name Server Operations Guide for BIND
-.SH COLOPHON
-This page is part of release 3.79 of the Linux
-.I man-pages
-project.
-A description of the project,
-information about reporting bugs,
-and the latest version of this page,
-can be found at
-\%http://www.kernel.org/doc/man\-pages/.
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