130 lines
3.9 KiB
Groff
130 lines
3.9 KiB
Groff
.\" $NetBSD: hosts.5,v 1.13 2003/08/07 10:31:17 agc Exp $
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.\"
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.\" Copyright (c) 1983, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)hosts.5 8.2 (Berkeley) 12/11/93
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.\"
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.Dd November 17, 2000
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.Dt HOSTS 5
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.Os
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.Sh NAME
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.Nm hosts
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.Nd host name data base
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.Sh DESCRIPTION
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The
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.Nm hosts
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file contains information regarding the known hosts on the network.
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It can be used in conjunction with the DNS, and the
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.Tn NIS
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maps
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.Sq hosts.byaddr ,
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and
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.Sq hosts.byname ,
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as controlled by
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.Xr nsswitch.conf 5 .
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.Pp
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For each host a single line should be present
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with the following information:
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.Dl address hostname [alias ...]
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.Pp
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These are:
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.Bl -tag -width hostname -compact -offset indent
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.It Em address
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Internet address
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.It Em hostname
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Official host name
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.It Em alias
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Alias host name
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.El
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.Pp
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Items are separated by any number of blanks and/or
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tab characters. A hash sign
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.Pq Dq \&#
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indicates the beginning of
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a comment; characters up to the end of the line are
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not interpreted by routines which search the file.
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.Pp
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When using the name server
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.Xr named 8 ,
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or
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.Xr ypserv 8 ,
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this file provides a backup when the name server
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is not running.
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For the name server, it is suggested that only a few addresses
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be included in this file.
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These include address for the local interfaces that
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.Xr ifconfig 8
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needs at boot time and a few machines on the local network.
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.Pp
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This file may be created from the official host
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data base maintained at the Network Information Control
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Center
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.Pq Tn NIC ,
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though local changes may be required
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to bring it up to date regarding unofficial aliases
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and/or unknown hosts. As the data base maintained at
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.Tn NIC
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is incomplete, use of the name server is recommended for
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sites on the
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.Tn DARPA
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Internet.
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.Pp
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As network addresses, both IPv4 and IPv6 addresses are allowed.
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IPv4 addresses are specified in the conventional dot
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.Pq Dq \&.
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notation using the
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.Xr inet_pton 3
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routine
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from the Internet address manipulation library,
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.Xr inet 3 .
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IPv6 addresses are specified in the standard hex-and-colon notation.
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Host names may contain any printable
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character other than a field delimiter, newline,
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or comment character.
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.Sh FILES
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.Bl -tag -width /etc/hosts -compact
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.It Pa /etc/hosts
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The
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.Nm hosts
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file resides in
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.Pa /etc .
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.El
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.Sh SEE ALSO
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.Xr gethostbyname 3 ,
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.Xr nsswitch.conf 5 ,
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.Xr ifconfig 8 ,
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.Xr named 8
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.Rs
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.%T "Name Server Operations Guide for BIND"
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.Re
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.Sh HISTORY
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The
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.Nm
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file format appeared in
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.Bx 4.2 .
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