hostname(5)                                                     hostname(5)




 NAME    [Toc]    [Back]
      hostname - host name resolution description

 DESCRIPTION    [Toc]    [Back]
      Hostnames are domains.  A domain is a hierarchical, dot-separated list
      of subdomains. For example, the machine monet, in the Berkeley
      subdomain of the EDU subdomain of the Internet Domain Name System
      would be represented as

           monet.Berkeley.EDU

      (with no trailing dot).

      Hostnames are often used with network client and server programs,
      which must generally translate the name to an address for use.  (This
      task is usually performed by the library routine gethostbyname(3N).)

      When NIS or the host table is being used for hostname resolution, the
      hostname is looked up without modification.  When DNS is used, the
      resolver may append domains to the hostname.

      The default method for resolving hostnames by the Internet name
      resolver is to follow RFC 1535's security recommendations.  Actions
      can be taken by the administrator to override these recommendations
      and to have the resolver behave the same as earlier, non-RFC 1535
      compliant resolvers.

      The default method (using RFC 1535 guidelines) follows:

      If the name consists of a single component, i.e. contains no dot, and
      if the environment variable HOSTALIASES is set to the name of a file,
      that file is searched for a string matching the input hostname.  The
      file should consist of lines made up of two strings separated by
      white-space, 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 there is at least one dot in the name, then the name is first tried
      as is.  The number of dots to cause this action is configurable by
      setting the threshold using the ndots option in /etc/resolv.conf
      (default: 1).  If the name ends with a dot, the trailing dot is
      removed, and the remaining name is looked up (regardless of the
      setting of the 'ndots' option) and no further processing is done.

      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.  If
      neither the search option in the /etc/resolv.conf file or the
      LOCALDOMAIN environment variable is used, then the search list of
      domains contains only the full domain specified by the domain option



 Hewlett-Packard Company            - 1 -   HP-UX 11i Version 2: August 2003






 hostname(5)                                                     hostname(5)




      (in /etc/resolv.conf) or the domain used in the local hostname (see
      resolver(4)).  For example, if the domain option is set to
      CS.Berkeley.EDU, then only CS.Berkeley.EDU will be in the search list
      and will be the only domain appended to the partial hostname, lithium,
      making lithium.CS.Berkeley.EDU the only name to be tried using the
      search list.

      If the search option is used in /etc/resolv.conf or the environment
      variable, LOCALDOMAIN, is set by the user, then the search list will
      include what is set by these methods. For example, if the search
      option contained

           CS.Berkeley.EDU CChem.Berkeley.EDU Berkeley.EDU    [Toc]    [Back]

      then the partial hostname (e.g., lithium) will be tried with each
      domain name appended (in the same order specified).  The resulting
      hostnames that would be tried are:

           lithium.CS.Berkeley.EDU
           lithium.CChem.Berkeley.EDU
           lithium.Berkeley.EDU

      The environment variable LOCALDOMAIN overrides the search and domain
      options, and if both options are present in the resolver configuration
      file, then only the last one listed is used (see resolver(4)).

      If the name was not previously tried ``as is'' (i.e., it fell below
      the ndots threshold or did not contain a dot), then the name, as
      originally provided, is attempted.

 AUTHOR    [Toc]    [Back]
      hostname was developed by the University of California, Berkeley.

 SEE ALSO    [Toc]    [Back]
      gethostent(3N), gethostbyname(3N), resolver(4), named(1M), RFC 1535.


 Hewlett-Packard Company            - 2 -   HP-UX 11i Version 2: August 2003