Apache: The Definitive Guide, 3rd Edition

A Subtle Problem

Note that you do not want to write:

Alias /somewhere_else/ /usr/www/APACHE3/somewhere_else

The trailing / on the alias will prevent things working. To understand this, imagine that you start with a web server that has a subdirectory called fred in its DocumentRoot. That is, there’s a directory called /www/docs/fred, and the Config file says:

DocumentRoot /www/docs

The URL http://your.webserver.com/fred fails because there is no file called fred. However, the request is redirected by Apache to http://your.webserver.com/fred/, which is then handled by looking for the directory index of /fred.

So, if you have a web page that says:

<a href="/fred">Take a look at fred</a>

it will work. When you click on “Take a look at fred,” you get redirected, and your browser looks for:

 http://your.webserver.com/fred/

as its URL, and all is well.

One day, you move fred to /some/where/else. You alter your Config file:

Alias /fred/ /some/where/else

or, equally ill-advisedly:

Alias /fred/ /some/where/else/

You put the trailing / on the aliases because you wanted to refer to a directory. But either will fail. Why?

The URL http://your.webserver.com/fred fails because there is no file /www/docs/fred anymore. In spite of the altered line in the Config file, this is what the URL still maps to, because /fred doesn’t match /fred/, and Apache no longer has a reason to redirect.

But using this Alias (without the trailing / on the alias):

Alias /fred /some/where/else

means that http://your.webserver.com/fred ...