Per-directory Configuration Files

AccessFilename .htaccess

An issue related to hosting multiple websites is that of providing hosting services for multiple clients. If the number of clients is significant, you may want to use per-directory configuration files. Per-directory configuration files are usually called htaccess files because they used to be used mostly for access control tasks. When this functionality is enabled, Apache will look for special configuration files in all directories leading to the file being requested. For example, if Apache receives a request for /usr/local/apache2/htdocs/index.html, it will look for per-directory configuration files in the /, /usr/, /usr/local/, /usr/local/apache2, and /usr/local/apache2/htdocs directories, in that order.

If found, the content for these configuration files is processed and merged with the main configuration from httpd.conf read at startup time. This is quite convenient for the system administrator, as it can allow users to self-manage their configurations. Also, since the files are parsed on-the-fly, the server does not need to be restarted for each change. On the downside, this has a performance penalty. Apache must perform expensive disk operations looking for these files in every request, even if the files do not exist.

The directive AccessFilename allows you to provide a list of filenames that Apache will look for when looking for per-directory configuration files.