.\" Copyright (c) 1983, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
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.\"    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
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.\"     @(#)hosts.5	8.2 (Berkeley) 12/11/93
.\" $FreeBSD$
.\"
.Dd December 11, 1993
.Dt HOSTS 5
.Os BSD 4.2
.Sh NAME
.Nm hosts
.Nd host name data base
.Sh DESCRIPTION
The
.Nm hosts
file contains information regarding
the known hosts on the network.
It can be used in conjunction with DNS, and the NIS
maps `hosts.byaddr' and `hosts.byname', as controlled by
.Xr nsswitch.conf 5 .
For each host a single line should be present
with the following information:
.Bd -unfilled -offset indent
Internet address
official host name
aliases
.Ed
.Pp
Items are separated by any number of blanks and/or
tab characters.  A ``#'' indicates the beginning of
a comment; characters up to the end of the line are
not interpreted by routines which search the file.
.Pp
When using the name server
.Xr named 8 ,
this file provides a backup used when the name server
is not running.
For the name server, it is suggested that only a few addresses
be included in this file.
These include addresses for the local interfaces that 
.Xr ifconfig 8
needs at boot time and a few machines on the local network.
.Pp
This file may be created from the official host
data base maintained at the Network Information Control
Center
.Pq Tn NIC , 
though local changes may be required
to bring it up to date regarding unofficial aliases
and/or unknown hosts.  As the data base maintained at
.Tn NIC
is incomplete, use of the name server is recommended for
sites on the
.Tn DARPA
Internet.
.Pp
Network addresses are specified in the conventional
``.'' (dot) notation using the
.Xr inet_addr 3
routine
from the Internet address manipulation library,
.Xr inet 3 .
Host names may contain any printable
character other than a field delimiter, newline,
or comment character.
.Sh FILES
.Bl -tag -width /etc/hosts -compact
.It Pa /etc/hosts
The
.Nm hosts
file resides in
.Pa /etc .
.El
.Sh SEE ALSO
.Xr gethostbyname 3 ,
.Xr nsswitch.conf 5 ,
.Xr ifconfig 8 ,
.Xr named 8
.Rs
.%T "Name Server Operations Guide for BIND"
.Re
.Sh HISTORY
The
.Nm
file format appeared in
.Bx 4.2 .