hostname(5)

hostname -- host name resolution description

Description

Hostnames are domains, where a domain is a hierarchical, dot-separated list of subdomains. For example, the machine laiter, in the Lachman subdomain of the COM subdomain of the ARPANET would be represented as

   laiter.Lachman.COM

(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. The name-to-address translation is generally performed by the library routine gethostbyname [see gethostent(3N)].

Hostnames are resolved by the Internet name resolver in the following fashion:

If the name consists of a single component (contains no dot), and if the environment variable HOSTALIASES is set to the name of a file, that file is searched for an 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-sensitive 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 in the local domain and its parent domains until either a match is found or fewer than two components of the local domain remain. For example, in the domain CHI.Lachman.COM, the name flaime.STG will be checked first as flaime.STG.CHI.Lachman.COM and then as flaime.STG.Lachman.COM. flaime.STG.COM will not be tried, as there is only one component remaining from the local domain.

References

gethostent(3N), named(1Mtcp), resolv.conf(4tcp)

RFC1035