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. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)hosts.5 8.2 (Berkeley) 12/11/93 33.\" 34.Dd December 11, 1993 35.Dt HOSTS 5 36.Os BSD 4.2 37.Sh NAME 38.Nm hosts 39.Nd host name data base 40.Sh DESCRIPTION 41The 42.Nm hosts 43file contains information regarding 44the known hosts on the network. 45For each host a single line should be present 46with the following information: 47.Bd -unfilled -offset indent 48official host name 49Internet address 50aliases 51.Ed 52.Pp 53Items are separated by any number of blanks and/or 54tab characters. A ``#'' 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 58When using the name server 59.Xr named 8 , 60this file provides a backup when the name server 61is not running. 62For the name server, it is suggested that only a few addresses 63be included in this file. 64These include address for the local interfaces that 65.Xr ifconfig 8 66needs at boot time and a few machines on the local network. 67.Pp 68This file may be created from the official host 69data base maintained at the Network Information Control 70Center 71.Pq Tn NIC , 72though local changes may be required 73to bring it up to date regarding unofficial aliases 74and/or unknown hosts. As the data base maintained at 75.Tn NIC 76is incomplete, use of the name server is recommended for 77sites on the 78.Tn DARPA 79Internet. 80.Pp 81Network addresses are specified in the conventional 82``.'' (dot) notation using the 83.Xr inet_addr 3 84routine 85from the Internet address manipulation library, 86.Xr inet 3 . 87Host names may contain any printable 88character other than a field delimiter, newline, 89or comment character. 90.Sh FILES 91.Bl -tag -width /etc/hosts -compact 92.It Pa /etc/hosts 93The 94.Nm hosts 95file resides in 96.Pa /etc . 97.El 98.Sh SEE ALSO 99.Xr gethostbyname 3 , 100.Xr ifconfig 8 , 101.Xr named 8 102.Rs 103.%T "Name Server Operations Guide for BIND" 104.Re 105.Sh HISTORY 106The 107.Nm 108file format appeared in 109.Bx 4.2 . 110