HOSTS(5) Debian GNU/Linux manual HOSTS(5)
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.
Aliases provide for name changes, alternate spellings, shorter host-
names, 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 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In modern systems, even though the host table has been superseded by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 sys-
tem 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.
isolatednodes
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.mydomain.org bar
216.234.231.5 master.debian.org master
205.230.163.103 www.opensource.org
HISTORICALNOTE
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 to date 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.
FILES
/etc/hosts
SEEALSO
hostname(1) resolver(3), resolver(5), hosts(5), hostname(7), named(8),
Internet RFC 952
AUTHOR
This manual page was written by Manoj Srivastava <srivasta debian.org>,
for the Debian GNU/Linux system.
Debian 2002-06-16 HOSTS(5)
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