focal (5) host.5.gz

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       In modern systems, even though the host table has been superseded by DNS, it is still widely used for

       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.mydomain.org  bar
        216.234.231.5   master.debian.org      master
        205.230.163.103 www.opensource.org

HISTORICAL NOTE

       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

SEE ALSO

       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.