hostname(7) — Linux manual page


hostname(7)         Miscellaneous Information Manual         hostname(7)

NAME         top

       hostname - hostname resolution description

DESCRIPTION         top

       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 "".

       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 NSS framework in glibc according to
       the hosts configuration in nsswitch.conf(5).  The DNS-based name
       resolver (in the dns NSS service module) resolves them 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

       If the input name ends with a trailing dot, the trailing dot is
       removed, and the remaining name is looked up with no further

       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, the name lithium.cchem
       will be checked first as lithium.cchem.cs.example and then as 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)).

SEE ALSO         top

       getaddrinfo(3), gethostbyname(3), nsswitch.conf(5), resolver(5),
       mailaddr(7), named(8)

       IETF RFC 1123 ⟨⟩

       IETF RFC 1178 ⟨

COLOPHON         top

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Linux man-pages 6.9.1          2024-05-02                    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)