hosts(5)

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   In  modern  systems,  even though the host table has been superseded by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

   # The following lines are desirable for IPv4 capable hosts
   127.0.0.1       localhost

   # 127.0.1.1 is often used for the FQDN of the machine
   127.0.1.1       thishost.mydomain.org  thishost
   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

   # The following lines are desirable for IPv6 capable hosts
   ::1             localhost ip6-localhost ip6-loopback
   ff02::1         ip6-allnodes
   ff02::2         ip6-allrouters

SEE ALSO

   hostname(1),  resolver(3),  host.conf(5),  resolv.conf(5), resolver(5),
   hostname(7), named(8)

   Internet RFC 952

COLOPHON

   This page is part of release 4.09 of the Linux  man-pages  project.   A
   description  of  the project, information about reporting bugs, and the
   latest    version    of    this    page,    can     be     found     at
   https://www.kernel.org/doc/man-pages/.

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