1HOSTS(5) Linux Programmer's Manual HOSTS(5)
2
6 hosts - The static table lookup for host names
7
9 /etc/hosts
10
12 This manual page describes the format of the /etc/hosts file. This file
13 is a simple text file that associates IP addresses with hostnames, one
14 line per IP address. For each host a single line should be present with
15 the following information:
16 IP_address canonical_hostname [aliases...]
18 Fields of the entry are separated by any number of blanks and/or tab
20 characters. Text from a "#" character until the end of the line is a
21 comment, and is ignored. Host names may contain only alphanumeric
22 characters, minus signs ("-"), and periods ("."). They must begin with
23 an alphabetic character and end with an alphanumeric character.
24 Optional aliases provide for name changes, alternate spellings, shorter
25 hostnames, or generic hostnames (for example, localhost).
26 The Berkeley Internet Name Domain (BIND) Server implements the Internet
28 name server for UNIX systems. It augments or replaces the /etc/hosts
29 file or host name lookup, and frees a host from relying on /etc/hosts
30 being up to date and complete.
31 In modern systems, even though the host table has been superseded by
33 DNS, it is still widely used for:
34 bootstrapping
36 Most systems have a small host table containing the name and
37 address information for important hosts on the local network.
38 This is useful when DNS is not running, for example during sys‐
39 tem bootup.
40 NIS Sites that use NIS use the host table as input to the NIS host
42 database. Even though NIS can be used with DNS, most NIS sites
43 still use the host table with an entry for all local hosts as a
44 backup.
45 isolated nodes
47 Very small sites that are isolated from the network use the host
48 table instead of DNS. If the local information rarely changes,
49 and the network is not connected to the Internet, DNS offers
50 little advantage.
51
53 127.0.0.1 localhost
54 192.168.1.10 foo.mydomain.org foo
55 192.168.1.13 bar.mydomain.org bar
56 146.82.138.7 master.debian.org master
57 209.237.226.90 www.opensource.org
58
60 Modifications to this file normally take effect immediately, except in
61 cases where the file is cached by applications.
62
64 RFC 952 gave the original format for the host table, though it has
65 since changed.
66 Before the advent of DNS, the host table was the only way of resolving
68 hostnames on the fledgling Internet. Indeed, this file could be created
69 from the official host data base maintained at the Network Information
70 Control Center (NIC), though local changes were often required to bring
71 it up to date regarding unofficial aliases and/or unknown hosts. The
72 NIC no longer maintains the hosts.txt files, though looking around at
73 the time of writing (circa 2000), there are historical hosts.txt files
74 on the WWW. I just found three, from 92, 94, and 95.
75
77 /etc/hosts
78
80 hostname(1), resolver(3), resolver(5), hostname(7), named(8), Internet
81 RFC 952
82
84 This manual page was written by Manoj Srivastava <srivasta@debian.org>,
85 for the Debian GNU/Linux system.
86Debian 2002-06-16 HOSTS(5)