hosts - The static table lookup for host names
Fields of the entry are separated by any number of blanks and/or tab characters. Text from a "#" character until the end of the line is a comment, and is ignored. Host names may contain any printable character other than a field delimiter, newline, or comment character. Aliases provide for name changes, alternate spellings, shorter hostnames, or generic hostnames (for example, localhost). The format of the host table is described in RFC:952.
The Berkeley Internet Name Domain (BIND) Server implements the Internet name server for UNIX systems. It replaces the /etc/hosts file or host name lookup, and frees a host from relying on /etc/hosts being up to date and complete.
In modern systems, even though the host table has been superseded by DNS, it is still widely used for:
Before the advent of DNS, the host table was the only way of resolving hostnames on the fledgling internet. Indeed, this file could be created from the official host data base maintained at the Network Information Control Center (NIC), though local changes were often required to bring it up todate regarding unofficial aliases and/or unknown hosts. The NIC no longer maintains the hosts.txt files, though looking around at the time of writing (circa 2000), there are historical hosts.txt files on the WWW. I just found three, from 92, 94, and 95.
This manual page was written by Manoj Srivastava (email@example.com), for the Debian GNU/Linux system.
Always put the FQDN first, if you don't do so hostname -f and other programs fail.