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NAME | DESCRIPTION | SEE ALSO | COLOPHON |
HOSTNAME(7) Linux Programmer's Manual HOSTNAME(7)
hostname - hostname resolution description
Hostnames are domains, where a domain is a hierarchical, dot-
separated list of subdomains; for example, the machine "monet", in
the "example" subdomain of the "com" domain would be represented as
"monet.example.com".
Each element of the hostname must be from 1 to 63 characters long and
the entire hostname, including the dots, can be at most 253
characters long. Valid characters for hostnames are ASCII(7) letters
from a to z, the digits from 0 to 9, and the hyphen (-). A hostname
may not start with a hyphen.
Hostnames are often used with network client and server programs,
which must generally translate the name to an address for use. (This
task is generally performed by either getaddrinfo(3) or the obsolete
gethostbyname(3).) Hostnames are resolved by the Internet name
resolver in the following fashion.
If the name consists of a single component, that is, contains no dot,
and if the environment variable HOSTALIASES is set to the name of a
file, that file is searched for any string matching the input
hostname. The file should consist of lines made up of two white-
space separated strings, the first of which is the hostname alias,
and the second of which is the complete hostname to be substituted
for that alias. If a case-insensitive match is found between the
hostname to be resolved and the first field of a line in the file,
the substituted name is looked up with no further processing.
If the input name ends with a trailing dot, the trailing dot is
removed, and the remaining name is looked up with no further
processing.
If the input name does not end with a trailing dot, it is looked up
by searching through a list of domains until a match is found. The
default search list includes first the local domain, then its parent
domains with at least 2 name components (longest first). For
example, in the domain cs.example.com, the name lithium.cchem will be
checked first as lithium.cchem.cs.example and then as
lithium.cchem.example.com. lithium.cchem.com will not be tried, as
there is only one component remaining from the local domain. The
search path can be changed from the default by a system-wide
configuration file (see resolver(5)).
getaddrinfo(3), gethostbyname(3), resolver(5), mailaddr(7), named(8)
IETF RFC 1123 ⟨http://www.ietf.org/rfc/rfc1123.txt⟩
IETF RFC 1178 ⟨http://www.ietf.org/rfc/rfc1178.txt⟩
This page is part of release 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2017-05-03 HOSTNAME(7)
Pages that refer to this page: getaddrinfo(3), getaddrinfo_a(3), gethostbyname(3), getnameinfo(3), resolver(3), host.conf(5), hostname(5), hosts(5), resolv.conf(5), sm-notify(8)