AllowOverride

This directive tells Apache which directives in an .htaccess file can override earlier directives.

AllowOverride override1 override2 ...
Directory 

The list of AllowOverride overrides is as follows:

AuthConfig

Allows individual settings of AuthDBMGroupFile, AuthDBMUserFile, AuthGroupFile, AuthName, AuthType, AuthUserFile, and require

FileInfo

Allows AddType, AddEncoding, AddLanguage, AddCharset, AddHandler, RemoveHandler, LanguagePriority, ErrorDocument, DefaultType, Action, Redirect, RedirectMatch, RedirectTemp, RedirectPermanent, PassEnv, SetEnv, UnsetEnv, Header, RewriteEnging, RewriteOptions, RewriteBase, RewriteCond, RewriteRule, CookieTracking, and Cookiename

Indexes

Allows FancyIndexing, AddIcon, AddDescription (see Chapter 7)

Limit

Can limit access based on hostname or IP number

Options

Allows the use of the Options directive (see Chapter 13)

All

All of the previous

None

None of the previous

You might ask: if none switches multiple searches off, which of these options switches it on? The answer is any of them, or the complete absence of AllowOverride. In other words, it is on by default.

To illustrate how this works, look at .../site.htaccess/httpd3.conf, which is httpd2.conf with the authentication directives on the salespeople's directory back in again. The Config filewants cleaners; the .myaccess file wants directors. If we now put the authorization directives, favoring cleaners, back into the Config file:

User webuser
Group webgroup
ServerName www.butterthlies.com
AccessFileName .myaccess

ServerAdmin sales@butterthlies.com
DocumentRoot /usr/www/APACHE3/site.htaccess/htdocs/salesmen
ErrorLog /usr/www/APACHE3/site.htaccess/logs/error_log
TransferLog /usr/www/APACHE3/site.htaccess/logs/access_log

ServerName sales.butterthlies.com

#AllowOverride None
AuthType Basic
AuthName darkness
AuthUserFile /usr/www/APACHE3/ok_users/sales
AuthGroupFile /usr/www/APACHE3/ok_users/groups
require group cleaners

and restart Apache, we find that we have to be a director (Bill or Ben). But, if we edit the Config file and uncomment the line:

...
AllowOverride None
...

we find that we have turned off the .htaccess method and that cleaners are back in fashion. In real life, the webmaster might impose a general policy of access control with this:

..
AllowOverride AuthConfig
...
require valid-user
...

The owners of the various pages could then limit their visitors further with this:

require group directors

See .../site.htaccess/httpd4.conf. As can be seen, AllowOverride makes it possible for individual directories to be precisely tailored.