When Apache receives a request, it is assumed that the client will be served a file out of the DocumentRoot directory. However, there will be times when you want these resources to be served from some other location. For example, if you wanted to place a set of documents on your Web site, it may be more convenient to leave them where they are, rather than to move them to a new location.
In this chapter, we deal with three general categories of these sorts of cases. Aliasing refers to mapping a URL to a particular directory. Redirecting refers to mapping a URL to another URL. And Rewriting refers to using mod_rewrite to alter the URL in some way.
Other recipes in this chapter are related because they map URLs to resources that are at unexpected places in the filesystem.
These topics are particularly interesting to Webmasters who want to avoid link-rot or have sites that are periodically subject to upheaval (files or directories are moved around, or even moved from server to server). The redirection and rewriting capabilities of the Apache Web server allow you to conceal such ugly behind-the-scenes disturbances from the eyes of your Internet visitors.
You want to serve content out of a directory other than the DocumentRoot directory. For example, you may have an existing directory of documents, which you want to have on your Web site but that you do not want to move into the Apache document root.