]>
Commit | Line | Data |
---|---|---|
06b00cff MK |
1 | .\" Copyright (c) 1987, 1990, 1993 |
2 | .\" The Regents of the University of California. All rights reserved. | |
3 | .\" | |
a9cd9cb7 | 4 | .\" %%%LICENSE_START(BSD_4_CLAUSE_UCB) |
06b00cff MK |
5 | .\" Redistribution and use in source and binary forms, with or without |
6 | .\" modification, are permitted provided that the following conditions | |
7 | .\" are met: | |
8 | .\" 1. Redistributions of source code must retain the above copyright | |
9 | .\" notice, this list of conditions and the following disclaimer. | |
10 | .\" 2. Redistributions in binary form must reproduce the above copyright | |
11 | .\" notice, this list of conditions and the following disclaimer in the | |
12 | .\" documentation and/or other materials provided with the distribution. | |
13 | .\" 3. All advertising materials mentioning features or use of this software | |
14 | .\" must display the following acknowledgement: | |
15 | .\" This product includes software developed by the University of | |
16 | .\" California, Berkeley and its contributors. | |
17 | .\" 4. Neither the name of the University nor the names of its contributors | |
18 | .\" may be used to endorse or promote products derived from this software | |
19 | .\" without specific prior written permission. | |
20 | .\" | |
21 | .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND | |
22 | .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
23 | .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
24 | .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE | |
25 | .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
26 | .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
27 | .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
28 | .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
29 | .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |
30 | .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
31 | .\" SUCH DAMAGE. | |
8c9302dc | 32 | .\" %%%LICENSE_END |
06b00cff MK |
33 | .\" |
34 | .\" @(#)hostname.7 8.2 (Berkeley) 12/30/93 | |
35 | .\" $FreeBSD: src/share/man/man7/hostname.7,v 1.7 2004/07/03 18:29:23 ru Exp $ | |
36 | .\" | |
37 | .\" 2008-06-11, mtk, Taken from FreeBSD 6.2 and modified for Linux. | |
38 | .\" | |
734882f4 | 39 | .TH HOSTNAME 7 2017-05-03 "Linux" "Linux Programmer's Manual" |
06b00cff | 40 | .SH NAME |
ddaec46d | 41 | hostname \- hostname resolution description |
06b00cff MK |
42 | .SH DESCRIPTION |
43 | Hostnames are domains, where a domain is a hierarchical, dot-separated | |
de5aebae MM |
44 | list of subdomains; for example, the machine "monet", in the "example" |
45 | subdomain of the "com" domain would be represented as "monet.example.com". | |
a721e8b2 | 46 | .PP |
fd923160 MM |
47 | Each element of the hostname must be from 1 to 63 characters long and the |
48 | entire hostname, including the dots, can be at most 253 characters long. | |
49 | Valid characters for hostnames are | |
50 | .BR ASCII (7) | |
51 | letters from | |
52 | .I a | |
53 | to | |
54 | .IR z , | |
55 | the digits from | |
56 | .I 0 | |
57 | to | |
58 | .IR 9 , | |
59 | and the hyphen (\-). | |
60 | A hostname may not start with a hyphen. | |
a721e8b2 | 61 | .PP |
06b00cff MK |
62 | Hostnames are often used with network client and server programs, |
63 | which must generally translate the name to an address for use. | |
64 | (This task is generally performed by either | |
65 | .BR getaddrinfo (3) | |
66 | or the obsolete | |
67 | .BR gethostbyname (3).) | |
921e2cfd FW |
68 | .PP |
69 | Hostnames are resolved by the NSS framework in glibc according | |
70 | to the | |
71 | .B hosts | |
72 | configuration in | |
73 | .BR nsswitch.conf . | |
74 | The DNS-based name resolver | |
75 | (in the | |
76 | .B dns | |
77 | NSS service module) resolves them in the following fashion. | |
a721e8b2 | 78 | .PP |
06b00cff MK |
79 | If the name consists of a single component, that is, contains no dot, |
80 | and if the environment variable | |
81 | .B HOSTALIASES | |
82 | is set to the name of a file, | |
83 | that file is searched for any string matching the input hostname. | |
84 | The file should consist of lines made up of two white-space separated strings, | |
85 | the first of which is the hostname alias, | |
86 | and the second of which is the complete hostname | |
87 | to be substituted for that alias. | |
88 | If a case-insensitive match is found between the hostname to be resolved | |
89 | and the first field of a line in the file, the substituted name is looked | |
90 | up with no further processing. | |
a721e8b2 | 91 | .PP |
06b00cff MK |
92 | If the input name ends with a trailing dot, |
93 | the trailing dot is removed, | |
94 | and the remaining name is looked up with no further processing. | |
a721e8b2 | 95 | .PP |
06b00cff MK |
96 | If the input name does not end with a trailing dot, it is looked up |
97 | by searching through a list of domains until a match is found. | |
98 | The default search list includes first the local domain, | |
99 | then its parent domains with at least 2 name components (longest first). | |
100 | For example, | |
de5aebae MM |
101 | in the domain cs.example.com, the name lithium.cchem will be checked first |
102 | as lithium.cchem.cs.example and then as lithium.cchem.example.com. | |
103 | lithium.cchem.com will not be tried, as there is only one component | |
06b00cff MK |
104 | remaining from the local domain. |
105 | The search path can be changed from the default | |
106 | by a system-wide configuration file (see | |
107 | .BR resolver (5)). | |
108 | .SH SEE ALSO | |
fd923160 | 109 | .BR getaddrinfo (3), |
06b00cff | 110 | .BR gethostbyname (3), |
921e2cfd | 111 | .BR nsswitch.conf (5), |
06b00cff MK |
112 | .BR resolver (5), |
113 | .BR mailaddr (7), | |
114 | .BR named (8) | |
a721e8b2 | 115 | .PP |
fd923160 MM |
116 | .UR http://www.ietf.org\:/rfc\:/rfc1123.txt |
117 | IETF RFC\ 1123 | |
118 | .UE | |
a721e8b2 | 119 | .PP |
fd923160 MM |
120 | .UR http://www.ietf.org\:/rfc\:/rfc1178.txt |
121 | IETF RFC\ 1178 | |
122 | .UE | |
06b00cff MK |
123 | .\" .SH HISTORY |
124 | .\" Hostname appeared in | |
125 | .\" 4.2BSD. |