1.\" Copyright (c) 1983, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)hosts.5 8.2 (Berkeley) 12/11/93 29.\" 30.Dd September 15, 2022 31.Dt HOSTS 5 32.Os 33.Sh NAME 34.Nm hosts 35.Nd host name data base 36.Sh DESCRIPTION 37The 38.Nm 39file contains information regarding 40the known hosts on the network. 41It can be used in conjunction with DNS, and the NIS 42maps `hosts.byaddr' and `hosts.byname', as controlled by 43.Xr nsswitch.conf 5 . 44For each host a single line should be present 45with the following information: 46.Bd -unfilled -offset indent 47Internet address 48official host name 49aliases 50.Ed 51.Pp 52Items are separated by any number of blanks and/or 53tab characters. 54A ``#'' indicates the beginning of 55a comment; characters up to the end of the line are 56not interpreted by routines which search the file. 57.Pp 58This file provides a backup used when the name server 59is not running. 60For the name server, it is suggested that only a few addresses 61be included in this file. 62These include addresses for the local interfaces that 63.Xr ifconfig 8 64needs at boot time and a few machines on the local network. 65.Pp 66Network addresses are specified in either the conventional 67``.'' (dot) notation for IPv4 or colon hexadecimal notation for IPv6, 68as understood by the 69.Xr inet_pton 3 70routine 71from the Internet address manipulation library, 72.Xr inet 3 . 73Host names may contain any printable 74character other than a field delimiter, newline, 75or comment character. 76.Sh FILES 77.Bl -tag -width /etc/hosts -compact 78.It Pa /etc/hosts 79The 80.Nm 81file resides in 82.Pa /etc . 83.El 84.Sh SEE ALSO 85.Xr gethostbyname 3 , 86.Xr inet 3 , 87.Xr nsswitch.conf 5 , 88.Xr ifconfig 8 89.Sh HISTORY 90The 91.Nm 92file format appeared in 93.Bx 4.1c . 94