Apache: The Definitive Guide, 3rd Edition

Chapter 8. Redirection

Few things are ever in exactly the right place at the right time, and this is as true of most web servers as of anything else. Alias and Redirect allow requests to be shunted about your filesystem or around the Web. Although in a perfect world it should never be necessary to do this, in practice it is often useful to move HTML files around on the server — or even to a different server — without having to change all the links in the HTML document.^[1] A more legitimate use — of Alias, at least — is to rationalize directories spread around the system. For example, they may be maintained by different users and may even be held on remotely mounted filesystems. But Alias can make them appear to be grouped in a more logical way.

A related directive, ScriptAlias, allows you to run CGI scripts, discussed in Chapter 16. You have a choice: everything that ScriptAlias does, and much more, can be done by the new Rewrite directive (described later in this chapter), but at a cost of some real programming effort. ScriptAlias is relatively simple to use, but it is also a good example of Apache’s modularity being a little less modular than we might like. Although ScriptAlias is defined in mod_alias.c in the Apache source code, it needs mod_cgi.c (or any module that does CGI) to function — it does, after all, run CGI scripts. mod_alias.c is compiled into Apache by default.

Some care is necessary in arranging the order of all these directives in the Config file. Generally, ...