Apache HOWTO documentation

How to:

How to redirect an entire server or directory

One way to redirect all requests for an entire server is to setup a Redirect to a cgi script which outputs a 301 or 302 status and the location of the other server.

By using a cgi-script you can intercept various requests and treat them specially, e.g. you might want to intercept POST requests, so that the client isn't redirected to a script on the other server which expects POST information (a redirect will lose the POST information.)

Here's how to redirect all requests to a script... In the server configuration file,

ScriptAlias / /usr/local/httpd/cgi-bin/redirect_script
and here's a simple perl script to redirect

print "Status: 302 Moved Temporarily\r
Location: http://www.some.where.else.com/\r\n\r\n";

How to reset your log files

Sooner or later, you'll want to reset your log files (access_log and error_log) because they are too big, or full of old information you don't need.

access.log typically grows by 1Mb for each 10,000 requests.

Most people's first attempt at replacingthe logfile is to just move the logfile or remove the logfile. This doesn't work.

Apache will continue writing to the logfile at the same offset as before the logifile moved. This results in a new logfile being created which is just as big as the old one, but it now contains thousands (or millions) of null characters.

The correct procedure is to move the logfile, then signal Apache to tell it to reopen the logfiles.

Apache is signalled using the SIGHUP (-1) signal. e.g.

mv access_log access_log.old ; kill -1 `cat httpd.pid`
Note: httpd.pid is a file containing the process id of the Apache httpd daemon, Apache saves this in the same directory as the log files.

Many people use this method to replace (and backup) their logfiles on a nightly basis.

How to stop robots

Ever wondered why so many clients are interested in a file called robots.txt which you don't have, and never did have?

These clients are called robots - special automated clients which wander around the web looking for interesting resources.

Most robots are used to generate some kind of web index which is then used by a search engine to help locate information.

robots.txt provides a means to request that robots limit their activities at the site, or more often than not, to leave the site alone.

When the first robots were developed, they had a bad reputation for sending hundreds of requests to each site, often resulting in the site being overloaded. Things have improved dramatically since then, thanks to Guidlines for Robot Writers, but even so, some robots may exhibit unfriendly behaviour which the webmaster isn't willing to tolerate.

Another reason some webmasters want to block access to robots, results from the way in which the information collected by the robots is subsequently indexed. There are currently no well used systems to annotate documents such that they can be indexed by wandering robots. Hence, the index writer will often revert to unsatisfactory algorithms to determine what gets indexed.

Typically, indexes are built around text which appears in document titles (<TITLE>), or main headings (<H1>), and more often than not, the words it indexes on are completely irrelevant or misleading for the docuement subject. The worst index is one based on every word in the document. This inevitably leads to the search engines offering poor suggestions which waste both the users and the servers valuable time

So if you decide to exclude robots completely, or just limit the areas in which they can roam, set up a robots.txt file, and refer to the robot exclusion documentation.

Much better systems exist to both index your site and publicise its resources, e.g. ALIWEB, which uses site defined index files.

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