105 lines
4.6 KiB
HTML
105 lines
4.6 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
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<!--Converted with LaTeX2HTML 96.1-c (Feb 29, 1996) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds -->
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<HTML>
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<HEAD>
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<TITLE>Writing hosts and networks Files</TITLE>
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</HEAD>
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<BODY LANG="EN">
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<A HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="contents_motif.gif"></A> <BR>
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<B> Next:</B> <A HREF="node65.html">Interface Configuration for IP</A>
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<B>Up:</B> <A HREF="node58.html">Configuring TCP/IP Networking</A>
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<B> Previous:</B> <A HREF="node63.html">Assigning IP-Addresses</A>
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<BR> <P>
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<H1><A NAME="SECTION007600000">Writing hosts and networks Files</A></H1>
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After you have sub-netted your network, you should prepare for some simple
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sort of hostname resolution using the /etc/hosts file. If you are
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not going to use DNS or NIS for address resolution, you have to put all
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hosts in the hosts file.
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<P>
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Even if you want to run DNS or NIS during normal operation, you want to
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have some subset of all hostnames in /etc/hosts nevertheless.
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For one, you want to have some sort of name resolution even when no
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network interfaces are running, for example during boot time. This is
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not only a matter of convenience, but also allows you to use symbolic
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hostnames in your rc.inet scripts. Thus, when changing
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IP-addresses, you only have to copy an updated hosts file to all
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machines and reboot, rather than having to edit a large number of
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rc files separately. Usually, you will put all local hostnames
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and addresses in hosts, adding those of any gateways and NIS
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servers if used.<A HREF="footnode.html#3165"><IMG ALIGN=BOTTOM ALT="gif" SRC="foot_motif.gif"></A>
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<P>
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Also, during initial testing, you should make sure your resolver only
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uses information from the hosts file. Your DNS or NIS software may
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come with sample files that may produce strange results when being used.
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To make all applications use /etc/hosts exclusively when looking
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up the IP-address of a host, you have to edit the /etc/host.conf
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file. Comment out any lines that begin with the keyword order
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by preceding them with a hash sign, and insert the line
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<Pre>
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order hosts
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</Pre>
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The configuration of the resolver library will be covered in detail
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in chapter-<A HREF="node80.html#resolv"><IMG ALIGN=BOTTOM ALT="gif" SRC="cross_ref_motif.gif"></A>.
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<P>
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The hosts file contains one entry per line, consisting of an
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IP-address, a hostname, and an optional list of aliases for the
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hostname. The fields are separated by spaces or tabs, and the address
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field must begin in column one. Anything following a hash sign (#) is
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regarded as a comment and is ignored.
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<P>
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Hostnames can be either fully qualified, or relative to the local
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domain. For vale, you would usually enter the the fully
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qualified name, vale.vbrew.com, and vale by itself in the
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hosts file, so that it is known by both its official name and the
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shorter local name.
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<P>
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This is an example how a hosts file at the Virtual Brewery
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might look. Two special names are included, vlager-if1 and
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vlager-if2 that give the addresses for both interfaces used
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on vlager.
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<a name="interfacefigsubnet"></a>
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<pre>
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#
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# Hosts file for Virtual Brewery/Virtual Winery
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#
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# IP local fully qualified domain name
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#
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127.0.0.1 localhost
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#
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191.72.1.1 vlager vlager.vbrew.com
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191.72.1.1 vlager-if1
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191.72.1.2 vstout vstout.vbrew.com
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191.72.1.3 vale vale.vbrew.com
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#
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191.72.2.1 vlager-if2
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191.72.2.2 vbeaujolais vbeaujolais.vbrew.com
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191.72.2.3 vbardolino vbardolino.vbrew.com
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191.72.2.4 vchianti vchianti.vbrew.com
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</pre>
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Just as with a host's IP-address, you sometimes would like to use a
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symbolic name for network numbers, too. Therefore, the hosts file
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has a companion called /etc/networks that maps network names to
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network numbers and vice versa. At the Virtual Brewery, we might install
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a networks file like this:<A HREF="footnode.html#3166"><IMG ALIGN=BOTTOM ALT="gif" SRC="foot_motif.gif"></A>
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<Pre>
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# /etc/networks for the Virtual Brewery
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brew-net 191.72.1.0
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wine-net 191.72.2.0
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</pre>
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<HR><A HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="contents_motif.gif"></A> <BR>
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<B> Next:</B> <A HREF="node65.html">Interface Configuration for IP</A>
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<B>Up:</B> <A HREF="node58.html">Configuring TCP/IP Networking</A>
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<B> Previous:</B> <A HREF="node63.html">Assigning IP-Addresses</A>
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<P><ADDRESS>
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<I>Andrew Anderson <BR>
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Thu Mar 7 23:22:06 EST 1996</I>
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</ADDRESS>
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