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1.1 root 1: .\" Copyright (c) 1987, 1990 The Regents of the University of California.
2: .\" All rights reserved.
3: .\"
4: .\" Redistribution and use in source and binary forms are permitted provided
5: .\" that: (1) source distributions retain this entire copyright notice and
6: .\" comment, and (2) distributions including binaries display the following
7: .\" acknowledgement: ``This product includes software developed by the
8: .\" University of California, Berkeley and its contributors'' in the
9: .\" documentation or other materials provided with the distribution and in
10: .\" all advertising materials mentioning features or use of this software.
11: .\" Neither the name of the University nor the names of its contributors may
12: .\" be used to endorse or promote products derived from this software without
13: .\" specific prior written permission.
14: .\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
15: .\" WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
16: .\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
17: .\"
18: .\" @(#)hostname.7 6.5 (Berkeley) 6/24/90
19: .\"
20: .Dd June 24, 1990
21: .Dt HOSTNAME 7
22: .Os BSD 4.2
23: .Sh NAME
24: .Nm hostname
25: .Nd host name resolution description
26: .Sh DESCRIPTION
27: Hostnames are domains, where a domain is a hierarchical, dot-separated
28: list of subdomains; for example, the machine monet, in the Berkeley
29: subdomain of the EDU subdomain of the Internet would be represented as
30: .Pp
31: .Dl monet.Berkeley.EDU
32: .Pp
33: (with no trailing dot).
34: .Pp
35: Hostnames are often used with network client and server programs,
36: which must generally translate the name to an address for use.
37: (This function is generally performed by the library routine
38: .Xr gethostbyname 3 . )
39: Hostnames are resolved by the Internet name resolver in the following
40: fashion.
41: .Pp
42: If the name consists of a single component, i.e. contains no dot,
43: and if the environment variable
44: .Dq Ev HOSTALIASES
45: is set to the name of a file,
46: that file is searched for an string matching the input hostname.
47: The file should consist of lines made up of two white-space separated strings,
48: the first of which is the hostname alias,
49: and the second of which is the complete hostname
50: to be substituted for that alias.
51: If a case-insensitive match is found between the hostname to be resolved
52: and the first field of a line in the file, the substituted name is looked
53: up with no further processing.
54: .Pp
55: If the input name ends with a trailing dot,
56: the trailing dot is removed,
57: and the remaining name is looked up with no further processing.
58: .Pp
59: If the input name does not end with a trailing dot, it is looked up
60: by searching through a list of domains until a match is found.
61: The default search list includes first the local domain,
62: then its parent domains with at least 2 name components (longest first).
63: For example,
64: in the domain CS.Berkeley.EDU, the name lithium.CChem will be checked first
65: as lithium.CChem.CS.Berkeley.EDU and then as lithium.CChem.Berkeley.EDU.
66: Lithium.CChem.EDU will not be tried, as the there is only one component
67: remaining from the local domain.
68: The search path can be changed from the default
69: by a system-wide configuration file (see
70: .Xr resolver 5 ) .
71: .Sh SEE ALSO
72: .Xr gethostbyname 3 ,
73: .Xr resolver 5 ,
74: .Xr mailaddr 7 ,
75: .Xr named 8
76: .Sh HISTORY
77: .Nm Hostname
78: appeared in 4.2 BSD.
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