/etc/hosts file in linux configure manual

Name
hosts - The static table lookup for host names
Synopsis
/etc/hosts
Description
This manual page describes the format of the /etc/hosts
file. This file is a simple text file that
associates IP addresses with hostnames, one line per IP address. For
each host a single line should be present with the following
information:
IP_address canonical_hostname [aliases...]
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 only alphanumeric characters, minus
signs ("-"), and periods ("."). They must begin with an alphabetic
character and end with
an alphanumeric character. Optional aliases provide for name changes,
alternate spellings, shorter hostnames, or generic hostnames (for
example,
localhost
).
The Berkeley Internet Name Domain (BIND) Server implements the
Internet name server for UNIX systems. It augments or 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In modern systems, even though the host table has been superseded by DNS, it is still widely used for:
bootstrapping
Most systems have a small host table containing the name and
address information for important hosts on the local network. This is
useful when DNS is not
running, for example during system bootup.
NIS
Sites that use NIS use the host table as input to the NIS host
database. Even though NIS can be used with DNS, most NIS sites still
use the host table with
an entry for all local hosts as a backup.
isolated nodes
Very small sites that are isolated from the network use the
host table instead of DNS. If the local information rarely changes, and
the network is not
connected to the Internet, DNS offers little advantage.
Example
127.0.0.1 localhost
192.168.1.10 foo.mydomain.org
foo
192.168.1.13 bar.mydomai