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Annotated edit history of hosts(5) version 3, including all changes. View license author blame.
Rev Author # Line
2 CraigBox 1 !!Name
1 perry 2
3 hosts - The static table lookup for host names
4
2 CraigBox 5 !!Synopsis
1 perry 6 __/etc/hosts__
7
2 CraigBox 8 !!Description
1 perry 9
2 CraigBox 10 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:
1 perry 11
2 CraigBox 12 IP_address canonical_hostname aliases
1 perry 13
2 CraigBox 14 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.
1 perry 15
2 CraigBox 16 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.
1 perry 17
2 CraigBox 18 In modern systems, even though the host table has been superseded by DNS, it is still widely used for:
1 perry 19
2 CraigBox 20 ; __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. (See TroubleshootingStartUp)
1 perry 21
2 CraigBox 22 ; __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.
1 perry 23
2 CraigBox 24 ; __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.
1 perry 25
2 CraigBox 26 !!Example
1 perry 27
28 127.0.0.1 localhost
2 CraigBox 29 192.168.1.10 foo.mydomain.org foo
30 192.168.1.13 bar.mydomain.org bar
31 216.234.231.5 master.debian.org master
32 205.230.163.103 www.opensource.org
1 perry 33
2 CraigBox 34 !Historical Note
1 perry 35
2 CraigBox 36 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 todate 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.
1 perry 37
2 CraigBox 38 !!Files
1 perry 39
40 ''/etc/hosts''
41
2 CraigBox 42 !!See Also
1 perry 43
3 PerryLorier 44 hostname(1) resolver(3), resolver(5), hosts(5), hostname(7), named(8), Internet RFC:952, host.conf(5)
1 perry 45
2 CraigBox 46 !!Author
1 perry 47
2 CraigBox 48 This manual page was written by Manoj Srivastava (srivasta@debian.org), for the Debian GNU/Linux system.
3 PerryLorier 49
50 !! Notes
51 !Always put the [FQDN] first
52 Always put the [FQDN] first, if you don't do so hostname -f and other programs fail.
53
54 !Avoid putting hostname on the same line as localhost
55 Avoid putting the FQDN of this machine with an IP address of localhost, it will confuse programs. If you must (because this host doesn't have any other IP addresses), good luck.
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