195 lines
5.4 KiB
HTML
195 lines
5.4 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of HOSTS</TITLE>
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</HEAD><BODY>
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<H1>HOSTS</H1>
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Section: Linux Programmer's Manual (5)<BR>Updated: 2017-09-15<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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hosts - static table lookup for hostnames
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>/etc/hosts</B>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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This manual page describes the format of the
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<I>/etc/hosts</I>
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file.
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This file is a simple text file that associates IP addresses
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with hostnames, one line per IP address.
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For each host a single
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line should be present with the following information:
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<DL COMPACT><DT id="1"><DD>
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<P>
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IP_address canonical_hostname [aliases...]
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</DL>
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<P>
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Fields of the entry are separated by any number of blanks and/or
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tab characters.
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Text from a "#" character until the end of the line is
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a comment, and is ignored.
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Host names may contain only alphanumeric
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characters, minus signs ("-"), and periods (".").
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They must begin with an
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alphabetic character and end with an alphanumeric character.
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Optional aliases provide for name changes, alternate spellings,
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shorter hostnames, or generic hostnames (for example,
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<I>localhost</I>).
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<P>
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The Berkeley Internet Name Domain (BIND) Server implements the
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Internet name server for UNIX systems.
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It augments or replaces the
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<I>/etc/hosts</I>
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file or hostname lookup, and frees a host from relying on
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<I>/etc/hosts</I>
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being up to date and complete.
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<P>
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In modern systems, even though the host table has been superseded by
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DNS, it is still widely used for:
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<DL COMPACT>
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<DT id="2"><B>bootstrapping</B>
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<DD>
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Most systems have a small host table containing the name and address
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information for important hosts on the local network.
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This is useful
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when DNS is not running, for example during system bootup.
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<DT id="3"><B>NIS</B>
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<DD>
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Sites that use NIS use the host table as input to the NIS host
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database.
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Even though NIS can be used with DNS, most NIS sites still
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use the host table with an entry for all local hosts as a backup.
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<DT id="4"><B>isolated nodes</B>
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<DD>
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Very small sites that are isolated from the network use the host table
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instead of DNS.
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If the local information rarely changes, and the
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network is not connected to the Internet, DNS offers little
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advantage.
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</DL>
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<A NAME="lbAE"> </A>
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<H2>FILES</H2>
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<I>/etc/hosts</I>
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<A NAME="lbAF"> </A>
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<H2>NOTES</H2>
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Modifications to this file normally take effect immediately,
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except in cases where the file is cached by applications.
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<A NAME="lbAG"> </A>
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<H3>Historical notes</H3>
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RFC 952 gave the original format for the host table, though it has
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since changed.
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<P>
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Before the advent of DNS, the host table was the only way of resolving
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hostnames on the fledgling Internet.
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Indeed, this file could be
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created from the official host data base maintained at the Network
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Information Control Center (NIC), though local changes were often
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required to bring it up to date regarding unofficial aliases and/or
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unknown hosts.
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The NIC no longer maintains the hosts.txt files,
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though looking around at the time of writing (circa 2000), there are
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historical hosts.txt files on the WWW.
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I just found three, from 92,
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94, and 95.
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<A NAME="lbAH"> </A>
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<H2>EXAMPLE</H2>
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# The following lines are desirable for IPv4 capable hosts
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127.0.0.1 localhost
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<P>
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# 127.0.1.1 is often used for the FQDN of the machine
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127.0.1.1 thishost.mydomain.org thishost
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192.168.1.10 foo.mydomain.org foo
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192.168.1.13 bar.mydomain.org bar
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146.82.138.7 master.debian.org master
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209.237.226.90 <A HREF="http://www.opensource.org">www.opensource.org</A>
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<P>
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# The following lines are desirable for IPv6 capable hosts
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::1 localhost ip6-localhost ip6-loopback
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ff02::1 ip6-allnodes
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ff02::2 ip6-allrouters
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<A NAME="lbAI"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?1+hostname">hostname</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?3+resolver">resolver</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?5+host.conf">host.conf</A></B>(5),
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<B><A HREF="/cgi-bin/man/man2html?5+resolv.conf">resolv.conf</A></B>(5),
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<B><A HREF="/cgi-bin/man/man2html?5+resolver">resolver</A></B>(5),
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<B><A HREF="/cgi-bin/man/man2html?7+hostname">hostname</A></B>(7),
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<B><A HREF="/cgi-bin/man/man2html?8+named">named</A></B>(8)
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<P>
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Internet RFC 952
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<A NAME="lbAJ"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="5"><A HREF="#lbAB">NAME</A><DD>
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<DT id="6"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="7"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="8"><A HREF="#lbAE">FILES</A><DD>
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<DT id="9"><A HREF="#lbAF">NOTES</A><DD>
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<DL>
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<DT id="10"><A HREF="#lbAG">Historical notes</A><DD>
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</DL>
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<DT id="11"><A HREF="#lbAH">EXAMPLE</A><DD>
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<DT id="12"><A HREF="#lbAI">SEE ALSO</A><DD>
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<DT id="13"><A HREF="#lbAJ">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:06:03 GMT, March 31, 2021
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</BODY>
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</HTML>
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