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.Dd September 15, 2022 29.Dt HOSTS 5 30.Os 31.Sh NAME 32.Nm hosts 33.Nd host name data base 34.Sh DESCRIPTION 35The 36.Nm 37file contains information regarding 38the known hosts on the network. 39It can be used in conjunction with DNS, and the NIS 40maps `hosts.byaddr' and `hosts.byname', as controlled by 41.Xr nsswitch.conf 5 . 42For each host a single line should be present 43with the following information: 44.Bd -unfilled -offset indent 45Internet address 46official host name 47aliases 48.Ed 49.Pp 50Items are separated by any number of blanks and/or 51tab characters. 52A ``#'' indicates the beginning of 53a comment; characters up to the end of the line are 54not interpreted by routines which search the file. 55.Pp 56This file provides a backup used when the name server 57is not running. 58For the name server, it is suggested that only a few addresses 59be included in this file. 60These include addresses for the local interfaces that 61.Xr ifconfig 8 62needs at boot time and a few machines on the local network. 63.Pp 64Network addresses are specified in either the conventional 65``.'' (dot) notation for IPv4 or colon hexadecimal notation for IPv6, 66as understood by the 67.Xr inet_pton 3 68routine 69from the Internet address manipulation library, 70.Xr inet 3 . 71Host names may contain any printable 72character other than a field delimiter, newline, 73or comment character. 74.Sh FILES 75.Bl -tag -width /etc/hosts -compact 76.It Pa /etc/hosts 77The 78.Nm 79file resides in 80.Pa /etc . 81.El 82.Sh SEE ALSO 83.Xr gethostbyname 3 , 84.Xr inet 3 , 85.Xr nsswitch.conf 5 , 86.Xr ifconfig 8 87.Sh HISTORY 88The 89.Nm 90file format appeared in 91.Bx 4.1c . 92