hosts(4) Kernel Interfaces Manual hosts(4)NAME
hosts - host name data base
DESCRIPTION
The file associates Internet (IP) addresses with official host names and aliases. This allows a user to refer to a host by a symbolic name
instead of an Internet address.
This file contain all addresses for local interfaces that needs at boot time (see ifconfig(1M)). When using the name server (see
named(1M)), or Network Information Service (see ypserv(1M)), this file often serves as a backup when the server is not running. In such
circumstances, it is a common practice for to contain a few addresses of machines on the local network.
should contain a single line for each host with the following information:
internet_address official_host_name aliases
The internet_address can be an IPv4 or IPv6 address specified in the conventional Internet dot notation. See inet(3N) or inet6(3N) for
more information on Internet address manipulation routines.
aliases are other names by which a host is known. They can substitute for the official_host_name in most commands. For example:
In this example, users can use remote login on by using the command:
instead of
If your system is in a domain naming environment, an official host name consists of the full domain extended host name. For example:
(space or tab character). Items are separated by any number or combination of space or tab characters (blanks). A character indicates the
beginning of a comment. Characters from the to the end of the line are not interpreted by routines that search the file. Trailing blanks
are allowed at the end of a line.
For the Internet, this file is normally created from the official host database maintained at the Network Information Control Center (NIC),
although local changes may be required to bring it up to date with respect to unofficial aliases and/or unknown hosts.
Host names can contain any printable character other than a white space, newline, or comment character.
EXAMPLES
See
AUTHOR
was developed by the University of California, Berkeley.
SEE ALSO gethostent(3N), inet(3N), nsswitch.conf(4).
hosts(4)
Check Out this Related Man Page
HOSTS(5) Linux Programmer's Manual HOSTS(5)NAME
hosts - The 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 3.27 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)