Apache: The Definitive Guide, Second Edition

3.4. Other Directives

Other housekeeping directives are listed here.

3.4.1. ServerName

ServerName hostname 
Server config, virtual host

ServerName gives the hostname of the server to use when creating redirection URLs, that is, if you use a <Location> directive or access a directory without a trailing "/".

3.4.2. UseCanonicalName

               UseCanonicalName on|off
Default: on 
Server config, virtual host, directory, .htaccess

This directive controls how Apache forms URLs that refer to itself, for example, when redirecting a request for http://www.domain.com/some/directory to the correct http://www.domain.com/some/directory/ (note the trailing "/" ). If UseCanonical-Name is on (the default), then the hostname and port used in the redirect will be those set by ServerName and Port. If it is off, then the name and port used will be the ones in the original request.

One instance where this directive may be useful is when users are in the same domain as the web server (for example, on an intranet). In this case, they may use the "short" name for the server (www, for example), instead of the fully qualified domain name (www.domain.com, say). If a user types a URL such as http://www/somedir (without the trailing slash), then, with UseCanonicalName switched on , the user will be directed to http://www.domain.com/somedir/, whereas with UseCanonicalName switched off, he or she will be redirected to http://www/somedir/. An obvious case in which this is useful is when user authentication is switched ...