1.\" $OpenBSD: hostname.7,v 1.11 2019/05/12 16:55:11 schwarze Exp $ 2.\" $NetBSD: hostname.7,v 1.4 1994/11/30 19:07:14 jtc Exp $ 3.\" 4.\" Copyright (c) 1987, 1990, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)hostname.7 8.2 (Berkeley) 12/30/93 32.\" 33.Dd $Mdocdate: May 12 2019 $ 34.Dt HOSTNAME 7 35.Os 36.Sh NAME 37.Nm hostname 38.Nd host name resolution description 39.Sh DESCRIPTION 40Hostnames are domains, where a domain is a hierarchical, dot-separated 41list of subdomains; for example, the machine monet, in the Berkeley 42subdomain of the EDU subdomain of the Internet would be represented as 43.Pp 44.Dl monet.Berkeley.EDU 45.Pp 46(with no trailing dot). 47.Pp 48Hostnames are often used with network client and server programs, 49which must generally translate the name to an address for use. 50(This function is generally performed by the library routine 51.Xr gethostbyname 3 . ) 52Hostnames are resolved by the Internet name resolver in the following 53fashion. 54.Pp 55If the input name ends with a trailing dot, 56the trailing dot is removed, 57and the remaining name is looked up with no further processing. 58.Pp 59If the input name does not end with a trailing dot, it is looked up 60by searching through a list of domains until a match is found. 61The default search list includes first the local domain, 62then its parent domains with at least 2 name components (longest first). 63For example, 64in the domain CS.Berkeley.EDU, the name lithium.CChem will be checked first 65as lithium.CChem.CS.Berkeley.EDU and then as lithium.CChem.Berkeley.EDU. 66Lithium.CChem.EDU will not be tried, as there is only one component 67remaining from the local domain. 68The search path can be changed from the default 69by a system-wide configuration file (see 70.Xr resolv.conf 5 ) . 71.Sh SEE ALSO 72.Xr gethostbyname 3 , 73.Xr resolv.conf 5 , 74.Xr nsd 8 , 75.Xr unbound 8 76.Sh HISTORY 77A 78.Nm 79manual page appeared in 80.Bx 4.2 . 81