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Mon Apr 25 13:37:00 UTC 2011 Slackware 13.37 x86_64 stable is released! Thanks to everyone who pitched in on this release: the Slackware team, the folks producing upstream code, and linuxquestions.org for providing a great forum for collaboration and testing. The ISOs are off to be replicated, a 6 CD-ROM 32-bit set and a dual-sided 32-bit/64-bit x86/x86_64 DVD. Please consider supporting the Slackware project by picking up a copy from store.slackware.com. We're taking pre-orders now, and offer a discount if you sign up for a subscription. As always, thanks to the Slackware community for testing, suggestions, and feedback. :-) Have fun!
181 lines
6.7 KiB
HTML
181 lines
6.7 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta name="generator" content="HTML Tidy, see www.w3.org" />
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<title>DNS Tools</title>
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<meta name="GENERATOR" content="Modular DocBook HTML Stylesheet Version 1.7" />
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<link rel="HOME" title="Slackware Linux Essentials" href="index.html" />
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<link rel="UP" title="Basic Network Commands" href="basic-network-commands.html" />
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<link rel="PREVIOUS" title="traceroute" href="basic-network-commands-traceroute.html" />
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<link rel="NEXT" title="finger" href="basic-network-commands-finger.html" />
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<link rel="STYLESHEET" type="text/css" href="docbook.css" />
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
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</head>
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<body class="SECT1" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#840084"
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alink="#0000FF">
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<div class="NAVHEADER">
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<table summary="Header navigation table" width="100%" border="0" cellpadding="0"
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cellspacing="0">
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<tr>
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<th colspan="3" align="center">Slackware Linux Essentials</th>
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</tr>
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<tr>
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<td width="10%" align="left" valign="bottom"><a
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href="basic-network-commands-traceroute.html" accesskey="P">Prev</a></td>
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<td width="80%" align="center" valign="bottom">Chapter 13 Basic Network Commands</td>
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<td width="10%" align="right" valign="bottom"><a
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href="basic-network-commands-finger.html" accesskey="N">Next</a></td>
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</tr>
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</table>
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<hr align="LEFT" width="100%" />
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</div>
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<div class="SECT1">
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<h1 class="SECT1"><a id="BASIC-NETWORK-COMMANDS-DNS"
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name="BASIC-NETWORK-COMMANDS-DNS">13.3 DNS Tools</a></h1>
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<p>Domain Name Service (DNS for short) is that magical protocol that allows your computer
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to turn meaningless domain names like www.slackware.com into meaningful IP address like
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<tt class="HOSTID">64.57.102.34</tt>. Computers can't route packets to www.slackware.com,
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but they can route packets to that domain name's IP address. This gives us a convenient
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way to remember machines. Without DNS we'd have to keep a mental database of just what IP
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address belongs to what computer, and that's assuming the IP address doesn't change.
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Clearly using names for computers is better, but how do we map names to IP addresses?</p>
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<div class="SECT2">
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<h2 class="SECT2"><a id="AEN4475" name="AEN4475">13.3.1 <tt
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class="COMMAND">host</tt></a></h2>
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<p><tt class="COMMAND">host</tt>(1) can do this for us. <tt class="COMMAND">host</tt> is
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used to map names to IP addresses. It is a very quick and simple utility without a lot of
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functions.</p>
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<table border="0" bgcolor="#E0E0E0" width="100%">
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<tr>
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<td>
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<pre class="SCREEN">
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<samp class="PROMPT">%</samp> <kbd class="USERINPUT">host www.slackware.com</kbd>
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www.slackware.com is an alias for slackware.com.
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slackware.com has address 64.57.102.34
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</pre>
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</td>
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</tr>
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</table>
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<p>But let's say for some reason we want to map an IP address to a domain name; what
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then?</p>
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</div>
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<div class="SECT2">
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<h2 class="SECT2"><a id="AEN4487" name="AEN4487">13.3.2 <tt
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class="COMMAND">nslookup</tt></a></h2>
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<p><tt class="COMMAND">nslookup</tt> is a tried and true program that has weathered the
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ages. <tt class="COMMAND">nslookup</tt> has been deprecated and may be removed from
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future releases. There is not even a man page for this program.</p>
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<table border="0" bgcolor="#E0E0E0" width="100%">
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<tr>
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<td>
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<pre class="SCREEN">
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<samp class="PROMPT">%</samp> <kbd class="USERINPUT">nslookup 64.57.102.34</kbd>
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Note: nslookup is deprecated and may be removed from future releases.
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Consider using the `dig' or `host' programs instead. Run nslookup with
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the `-sil[ent]' option to prevent this message from appearing.
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Server: 192.168.1.254
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Address: 192.168.1.254#53
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Non-authoritative answer:
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www.slackware.com canonical name = slackware.com.
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Name: slackware.com
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Address: 64.57.102.34
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</pre>
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</td>
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</tr>
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</table>
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</div>
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<div class="SECT2">
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<h2 class="SECT2"><a id="AEN4496" name="AEN4496">13.3.3 <tt
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class="COMMAND">dig</tt></a></h2>
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<p>The meanest dog in the pound, the domain information groper, <tt
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class="COMMAND">dig</tt>(1) for short, is the go-to program for finding DNS information.
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<tt class="COMMAND">dig</tt> can grab just about anything from a DNS server including
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reverse lookups, A, CNAME, MX, SP, and TXT records. <tt class="COMMAND">dig</tt> has many
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command line options and if you're not familiar with it you should read through it's
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extensive man page.</p>
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<table border="0" bgcolor="#E0E0E0" width="100%">
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<tr>
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<td>
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<pre class="SCREEN">
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<samp class="PROMPT">%</samp> <kbd
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class="USERINPUT">dig @192.168.1.254 www.slackware.com mx</kbd>
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; <<>> DiG 9.2.2 <<>> @192.168.1.254 www.slackware.com mx
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;; global options: printcmd
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;; Got answer:
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;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 26362
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;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 2, ADDITIONAL: 2
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;; QUESTION SECTION:
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;www.slackware.com. IN MX
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;; ANSWER SECTION:
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www.slackware.com. 76634 IN CNAME slackware.com.
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slackware.com. 86400 IN MX 1 mail.slackware.com.
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;; AUTHORITY SECTION:
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slackware.com. 86400 IN NS ns1.cwo.com.
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slackware.com. 86400 IN NS ns2.cwo.com.
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;; ADDITIONAL SECTION:
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ns1.cwo.com. 163033 IN A 64.57.100.2
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ns2.cwo.com. 163033 IN A 64.57.100.3
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;; Query time: 149 msec
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;; SERVER: 192.168.1.254#53(192.168.1.254)
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;; WHEN: Sat Nov 6 16:59:31 2004
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;; MSG SIZE rcvd: 159
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</pre>
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</td>
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</tr>
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</table>
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<p>This should give you an idea how <tt class="COMMAND">dig</tt> works.
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“@192.168.1.254” specifies the dns server to use.
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“www.slackware.com” is the domain name I am performing a lookup on, and
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“mx” is the type of lookup I am performing. The above query tells me that
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e-mail to <tt class="HOSTID">www.slackware.com</tt> will instead be sent to <tt
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class="HOSTID">mail.slackware.com</tt> for delivery.</p>
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</div>
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</div>
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<div class="NAVFOOTER">
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<hr align="LEFT" width="100%" />
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<table summary="Footer navigation table" width="100%" border="0" cellpadding="0"
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cellspacing="0">
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<tr>
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<td width="33%" align="left" valign="top"><a
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href="basic-network-commands-traceroute.html" accesskey="P">Prev</a></td>
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<td width="34%" align="center" valign="top"><a href="index.html"
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accesskey="H">Home</a></td>
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<td width="33%" align="right" valign="top"><a href="basic-network-commands-finger.html"
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accesskey="N">Next</a></td>
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</tr>
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<tr>
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<td width="33%" align="left" valign="top"><tt class="COMMAND">traceroute</tt></td>
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<td width="34%" align="center" valign="top"><a href="basic-network-commands.html"
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accesskey="U">Up</a></td>
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<td width="33%" align="right" valign="top"><tt class="COMMAND">finger</tt></td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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