NAME

       hosts - static table lookup for hostnames

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 hostname 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       In modern systems, even though the host table has been superseded by DNS, it is still widely used for: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.

FILES

       /etc/hosts

NOTES

       Modifications to this file normally take effect immediately, except in cases where the file is cached  by
       applications.

   Historical notes
       RFC 952 gave the original format for the host table, though it has since changed.

       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.

EXAMPLE

       127.0.0.1       localhost
       192.168.1.10    foo.mydomain.org       foo
       192.168.1.13    bar.mydomain.org       bar
       146.82.138.7    master.debian.org      master
       209.237.226.90  www.opensource.org

SEE ALSO

       hostname(1), resolver(3), resolver(5), hostname(7), named(8)

       Internet RFC 952

COLOPHON

       This page is part of release 3.54 of the Linux man-pages project.  A  description  of  the  project,  and
       information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.

Linux                                              2002-06-16                                           HOSTS(5)