89 lines
3.8 KiB
Groff
89 lines
3.8 KiB
Groff
.\" Copyright (c) 1987, 1990, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)hostname.7 8.2 (Berkeley) 12/30/93
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.\" $FreeBSD$
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.\"
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.Dd December 25, 2013
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.Dt HOSTNAME 7
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.Os
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.Sh NAME
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.Nm hostname
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.Nd host name resolution description
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.Sh DESCRIPTION
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Hostnames are domains, where a domain is a hierarchical, dot-separated
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list of subdomains; for example, the machine monet, in the Berkeley
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subdomain of the EDU subdomain of the Internet would be represented as
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.Pp
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.Dl monet.Berkeley.EDU
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.Pp
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(with no trailing dot).
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.Pp
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Hostnames are often used with network client and server programs,
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which must generally translate the name to an address for use.
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(This function is generally performed by the library routine
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.Xr gethostbyname 3 . )
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Hostnames are resolved by the Internet name resolver in the following
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fashion.
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.Pp
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If the name consists of a single component, i.e., contains no dot,
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and if the environment variable
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.Dq Ev HOSTALIASES
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is set to the name of a file,
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that file is searched for any string matching the input hostname.
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The file should consist of lines made up of two white-space separated strings,
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the first of which is the hostname alias,
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and the second of which is the complete hostname
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to be substituted for that alias.
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If a case-insensitive match is found between the hostname to be resolved
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and the first field of a line in the file, the substituted name is looked
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up with no further processing.
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.Pp
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If the input name ends with a trailing dot,
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the trailing dot is removed,
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and the remaining name is looked up with no further processing.
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.Pp
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If the input name does not end with a trailing dot, it is looked up
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by searching through a list of domains until a match is found.
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The default search list includes first the local domain,
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then its parent domains with at least 2 name components (longest first).
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For example,
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in the domain CS.Berkeley.EDU, the name lithium.CChem will be checked first
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as lithium.CChem.CS.Berkeley.EDU and then as lithium.CChem.Berkeley.EDU.
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Lithium.CChem.EDU will not be tried, as there is only one component
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remaining from the local domain.
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The search path can be changed from the default
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by a system-wide configuration file (see
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.Xr resolver 5 ) .
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.Sh SEE ALSO
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.Xr gethostbyname 3 ,
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.Xr resolver 5
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.Sh HISTORY
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.Nm Hostname
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appeared in
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.Bx 4.2 .
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