hostname

HOSTNAME(7)                 Linux Programmer's Manual                HOSTNAME(7)



NAME
       hostname - hostname resolution description

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 NSS framework in glibc according to the
       hosts configuration in nsswitch.conf.  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 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)).

SEE ALSO
       getaddrinfo(3), gethostbyname(3), nsswitch.conf(5), 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.txtCOLOPHON
       This page is part of release 5.10 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                              2019-05-09                        HOSTNAME(7)