2004-11-03 13:51:07 +00:00
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.\" Hey, Emacs! This is an -*- nroff -*- source file.
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.\" Copyright (c) 2000 Manoj Srivastava <srivasta@debian.org>
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.\"
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.\" This is free documentation; you can redistribute it and/or
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.\" modify it under the terms of the GNU General Public License as
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.\" published by the Free Software Foundation; either version 2 of
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.\" the License, or (at your option) any later version.
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.\"
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.\" The GNU General Public License's references to "object code"
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.\" and "executables" are to be interpreted as the output of any
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.\" document formatting or typesetting system, including
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.\" intermediate and printed output.
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.\"
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.\" This manual is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public
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.\" License along with this manual; if not, write to the Free
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.\" Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139,
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.\" USA.
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.\"
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.\" Minor polishing, aeb
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.\" Modified, 2002-06-16, Mike Coleman
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.\"
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2007-05-18 10:09:18 +00:00
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.TH HOSTS 5 2002-06-16 "Linux" "Linux Programmer's Manual"
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2004-11-03 13:51:07 +00:00
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.SH NAME
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2010-10-30 05:38:50 +00:00
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hosts \- static table lookup for hostnames
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2004-11-03 13:51:07 +00:00
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.SH SYNOPSIS
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.B /etc/hosts
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.SH DESCRIPTION
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2007-04-12 22:42:49 +00:00
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This manual page describes the format of the
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.I /etc/hosts
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file.
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This file is a simple text file that associates IP addresses
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with hostnames, one line per IP address.
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For each host a single
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line should be present with the following information:
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.RS
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.PP
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2005-05-11 15:14:54 +00:00
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IP_address canonical_hostname [aliases...]
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.RE
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.PP
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Fields of the entry are separated by any number of blanks and/or
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tab characters.
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Text from a "#" character until the end of the line is
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a comment, and is ignored.
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Host names may contain only alphanumeric
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characters, minus signs ("\-"), and periods (".").
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They must begin with an
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alphabetic character and end with an alphanumeric character.
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Optional aliases provide for name changes, alternate spellings,
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shorter hostnames, or generic hostnames (for example,
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.IR localhost ).
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.PP
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The Berkeley Internet Name Domain (BIND) Server implements the
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intro.1, time.1, accept.2, bind.2, connect.2, execve.2, flock.2, getdents.2, getpriority.2, getuid.2, intro.2, ioctl.2, mincore.2, mknod.2, personality.2, ptrace.2, read.2, recv.2, select_tut.2, send.2, sendfile.2, shmctl.2, sigaction.2, signal.2, stat.2, times.2, truncate.2, umask.2, wait.2, MB_CUR_MAX.3, MB_LEN_MAX.3, argz_add.3, btowc.3, clearenv.3, clock.3, cmsg.3, end.3, endian.3, errno.3, exit.3, fgetwc.3, fgetws.3, fopen.3, fputwc.3, fputws.3, fseek.3, fwide.3, getfsent.3, getgrnam.3, gethostid.3, getipnodebyname.3, getmntent.3, getpwnam.3, getwchar.3, grantpt.3, iconv.3, iconv_close.3, iconv_open.3, insque.3, intro.3, iswalnum.3, iswalpha.3, iswblank.3, iswcntrl.3, iswctype.3, iswdigit.3, iswgraph.3, iswlower.3, iswprint.3, iswpunct.3, iswspace.3, iswupper.3, iswxdigit.3, malloc.3, mblen.3, mbrlen.3, mbrtowc.3, mbsinit.3, mbsnrtowcs.3, mbsrtowcs.3, mbstowcs.3, mbtowc.3, mkstemp.3, mktemp.3, nl_langinfo.3, openpty.3, posix_openpt.3, printf.3, ptsname.3, putwchar.3, qecvt.3, rcmd.3, readdir.3, rexec.3, rpc.3, setnetgrent.3, shm_open.3, sigpause.3, stdin.3, stpcpy.3, strftime.3, strptime.3, syslog.3, towctrans.3, towlower.3, towupper.3, ttyslot.3, ungetwc.3, unlocked_stdio.3, wcpcpy.3, wcpncpy.3, wcrtomb.3, wcscasecmp.3, wcscat.3, wcschr.3, wcscmp.3, wcscpy.3, wcscspn.3, wcsdup.3, wcslen.3, wcsncasecmp.3, wcsncat.3, wcsncmp.3, wcsncpy.3, wcsnlen.3, wcsnrtombs.3, wcspbrk.3, wcsrchr.3, wcsrtombs.3, wcsspn.3, wcsstr.3, wcstok.3, wcstombs.3, wcswidth.3, wctob.3, wctomb.3, wctrans.3, wctype.3, wcwidth.3, wmemchr.3, wmemcmp.3, wmemcpy.3, wmemmove.3, wmemset.3, wprintf.3, console_ioctl.4, pts.4, elf.5, filesystems.5, hosts.5, proc.5, ttytype.5, boot.7, capabilities.7, credentials.7, epoll.7, glob.7, koi8-r.7, path_resolution.7, pty.7, signal.7, suffixes.7, time.7, unicode.7, unix.7, uri.7, utf-8.7: global fix: s/Unix/UNIX/
The man pages were rather inconsistent in the use of "Unix"
versus "UNIX". Let's go with the trademark usage.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2010-10-12 04:45:38 +00:00
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Internet name server for UNIX systems.
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It augments or replaces the
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.I /etc/hosts
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2008-06-27 03:37:56 +00:00
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file or hostname lookup, and frees a host from relying on
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.I /etc/hosts
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being up to date and complete.
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.PP
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In modern systems, even though the host table has been superseded by
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DNS, it is still widely used for:
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.TP
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.B bootstrapping
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Most systems have a small host table containing the name and address
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information for important hosts on the local network.
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This is useful
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when DNS is not running, for example during system bootup.
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2004-11-03 13:51:07 +00:00
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.TP
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.B NIS
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Sites that use NIS use the host table as input to the NIS host
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database.
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Even though NIS can be used with DNS, most NIS sites still
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use the host table with an entry for all local hosts as a backup.
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.TP
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.B isolated nodes
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Very small sites that are isolated from the network use the host table
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instead of DNS.
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If the local information rarely changes, and the
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network is not connected to the Internet, DNS offers little
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advantage.
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2007-05-19 04:30:20 +00:00
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.SH FILES
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.I /etc/hosts
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2007-05-16 02:54:18 +00:00
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.SH NOTES
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2005-05-11 15:14:54 +00:00
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Modifications to this file normally take effect immediately,
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except in cases where the file is cached by applications.
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2007-05-16 02:54:18 +00:00
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.SS "Historical Notes"
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RFC\ 952 gave the original format for the host table, though it has
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since changed.
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Before the advent of DNS, the host table was the only way of resolving
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hostnames on the fledgling Internet.
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Indeed, this file could be
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created from the official host data base maintained at the Network
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Information Control Center (NIC), though local changes were often
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required to bring it up to date regarding unofficial aliases and/or
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unknown hosts.
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The NIC no longer maintains the hosts.txt files,
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though looking around at the time of writing (circa 2000), there are
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historical hosts.txt files on the WWW.
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I just found three, from 92,
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94, and 95.
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2007-05-19 04:30:20 +00:00
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.SH EXAMPLE
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.nf
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127.0.0.1 localhost
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192.168.1.10 foo.mydomain.org foo
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192.168.1.13 bar.mydomain.org bar
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146.82.138.7 master.debian.org master
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209.237.226.90 www.opensource.org
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.fi
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.SH "SEE ALSO"
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.BR hostname (1),
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.BR resolver (3),
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.BR resolver (5),
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.BR hostname (7),
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.BR named (8),
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2005-07-20 07:50:45 +00:00
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Internet RFC\ 952
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2007-05-16 03:40:19 +00:00
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.\" .SH AUTHOR
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.\" This manual page was written by Manoj Srivastava <srivasta@debian.org>,
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.\" for the Debian GNU/Linux system.
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