Introduction to the Apache Web Server - ApacheCon

8.3 Alias
• Maps a URL to a directory, often outside of the DocumentRoot directory
Used to map a URL to a directory - usually a directory outside of the main document directory, although
this is not necessarily the case. The default distro, for example, comes with an Alias for the documentation
(/manual) which points to a directory within the document root. This is so that you can move it if you want
to, but is really rather redundant. For one release (1.3.25 perhaps?) /manual actually did move outside of
the document root, but it moved back in the next release because it irritated people who don’t like change.
The Alias for /icons/, on the other hand, points to a directory that has always been outside of the document
root.
Important note about Alias. The slashes must match. That is, if the first argument contains a slash, the
second one should also. Thus:
Alias /foo /var/www/foo
Note that the first argument (/foo) has no trailing slash, and, thus, the second argument (/var/www/foo)
also should not. When the slashes don’t match, bad things happen. Alias is taken very literally. The string
in the URL is replaced verbatim with the argument provided. This can result in file paths with too many
slashes, or two few, depending on which side you erred.
For example, if you have:
Alias /icons/ /usr/local/apache/icons
You will end up with errors in your logs which say something like:
File /usr/local/apache/iconssomething.gif not found
Note the missing / between icons and something.gif. That’s your clue that this is what is happening.
8.4 ScriptAlias
• Maps a URL to a directory, and indicates that the directory contains CGI programs
ScriptAlias /cgi-bin/ /usr/local/apache/cgi-bin/
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