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148 lines
5.9 KiB
HTML
148 lines
5.9 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<HTML>
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<HEAD>
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<META NAME="description" CONTENT="Some 'how to' tips for the Apache httpd server">
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<META NAME="keywords" CONTENT="apache,redirect,robots,rotate,logfiles">
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<TITLE>Apache HOWTO documentation</TITLE>
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</HEAD>
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<!-- Background white, links blue (unvisited), navy (visited), red (active) -->
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<BODY
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BGCOLOR="#FFFFFF"
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TEXT="#000000"
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LINK="#0000FF"
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VLINK="#000080"
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ALINK="#FF0000"
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>
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<!--#include virtual="header.html" -->
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<H1 ALIGN="CENTER">Apache HOWTO documentation</H1>
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How to:
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<ul>
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<li><A HREF="#redirect">redirect an entire server or directory to a single URL</A>
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<li><A HREF="#logreset">reset your log files</A>
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<li><A HREF="#stoprob">stop/restrict robots</A>
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</ul>
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<HR>
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<H2><A name="redirect">How to redirect an entire server or directory to a single URL</A></H2>
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<P>There are two chief ways to redirect all requests for an entire
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server to a single location: one which requires the use of
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<code>mod_rewrite</code>, and another which uses a CGI script.
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<P>First: if all you need to do is migrate a server from one name to
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another, simply use the <code>Redirect</code> directive, as supplied
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by <code>mod_alias</code>:
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<blockquote><pre>
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Redirect / http://www.apache.org/
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</pre></blockquote>
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<P>Since <code>Redirect</code> will forward along the complete path,
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however, it may not be appropriate - for example, when the directory
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structure has changed after the move, and you simply want to direct people
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to the home page.
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<P>The best option is to use the standard Apache module <code>mod_rewrite</code>.
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If that module is compiled in, the following lines:
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<blockquote><pre>RewriteEngine On
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RewriteRule /.* http://www.apache.org/ [R]
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</pre></blockquote>
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This will send an HTTP 302 Redirect back to the client, and no matter
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what they gave in the original URL, they'll be sent to
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"http://www.apache.org".
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The second option is to set up a <CODE>ScriptAlias</Code> pointing to
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a <B>cgi script</B> which outputs a 301 or 302 status and the location
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of the other server.</P>
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<P>By using a <B>cgi-script</B> you can intercept various requests and
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treat them specially, e.g. you might want to intercept <B>POST</B>
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requests, so that the client isn't redirected to a script on the other
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server which expects POST information (a redirect will lose the POST
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information.) You might also want to use a CGI script if you don't
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want to compile mod_rewrite into your server.
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<P>Here's how to redirect all requests to a script... In the server
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configuration file,
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<blockquote><pre>ScriptAlias / /usr/local/httpd/cgi-bin/redirect_script</pre></blockquote>
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and here's a simple perl script to redirect requests:
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<blockquote><pre>
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#!/usr/local/bin/perl
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print "Status: 302 Moved Temporarily\r
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Location: http://www.some.where.else.com/\r\n\r\n";
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</pre></blockquote></P>
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<HR>
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<H2><A name="logreset">How to reset your log files</A></H2>
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<P>Sooner or later, you'll want to reset your log files (access_log and
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error_log) because they are too big, or full of old information you don't
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need.</P>
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<P><CODE>access.log</CODE> typically grows by 1Mb for each 10,000 requests.</P>
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<P>Most people's first attempt at replacing the logfile is to just move the
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logfile or remove the logfile. This doesn't work.</P>
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<P>Apache will continue writing to the logfile at the same offset as before the
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logfile moved. This results in a new logfile being created which is just
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as big as the old one, but it now contains thousands (or millions) of null
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characters.</P>
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<P>The correct procedure is to move the logfile, then signal Apache to tell it to reopen the logfiles.</P>
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<P>Apache is signaled using the <B>SIGHUP</B> (-1) signal. e.g.
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<blockquote><code>
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mv access_log access_log.old<BR>
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kill -1 `cat httpd.pid`
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</code></blockquote>
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</P>
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<P>Note: <code>httpd.pid</code> is a file containing the <B>p</B>rocess <B>id</B>
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of the Apache httpd daemon, Apache saves this in the same directory as the log
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files.</P>
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<P>Many people use this method to replace (and backup) their logfiles on a
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nightly or weekly basis.</P>
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<HR>
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<H2><A name="stoprob">How to stop or restrict robots</A></H2>
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<P>Ever wondered why so many clients are interested in a file called
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<code>robots.txt</code> which you don't have, and never did have?</P>
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<P>These clients are called <B>robots</B> (also known as crawlers,
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spiders and other cute name) - special automated clients which
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wander around the web looking for interesting resources.</P>
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<P>Most robots are used to generate some kind of <em>web index</em> which
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is then used by a <em>search engine</em> to help locate information.</P>
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<P><code>robots.txt</code> provides a means to request that robots limit their
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activities at the site, or more often than not, to leave the site alone.</P>
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<P>When the first robots were developed, they had a bad reputation for sending hundreds/thousands of requests to each site, often resulting in the site being overloaded. Things have improved dramatically since then, thanks to <A HREF="http://info.webcrawler.com/mak/projects/robots/guidelines.html"> Guidelines for Robot Writers</A>, but even so, some robots may <A HREF="http://www.zyzzyva.com/robots/alert/">exhibit unfriendly behavior</A> which the webmaster isn't willing to tolerate, and will want to stop.</P>
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<P>Another reason some webmasters want to block access to robots, is to
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stop them indexing dynamic information. Many search engines will use the
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data collected from your pages for months to come - not much use if your
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serving stock quotes, news, weather reports or anything else that will be
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stale by the time people find it in a search engine.</P>
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<P>If you decide to exclude robots completely, or just limit the areas
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in which they can roam, create a <CODE>robots.txt</CODE> file; refer
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to the <A HREF="http://info.webcrawler.com/mak/projects/robots/robots.html">robot information pages</A> provided by Martijn Koster for the syntax.</P>
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<!--#include virtual="footer.html" -->
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</BODY>
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</HTML>
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