Ever since I moved to Linux, I noted some strange behaviour. In Ubuntu, http://localhost/index works but on WAMP it does not work. I tested this with APACHE's rewrite module set to off on both. Any good explanation?

Apache.conf (LAMP)

etc/apache2/sites-enabled/000-default

<VirtualHost *:80>
    ServerAdmin webmaster@localhost

    DocumentRoot /var/www
    <Directory />
        Options FollowSymLinks
        AllowOverride None
    </Directory>
    <Directory /var/www/>
        Options Indexes FollowSymLinks MultiViews
        AllowOverride None
        Order allow,deny
        allow from all
    </Directory>

Apache.conf WAMP

<Directory "C:/wamp/www/">
    #
    # Possible values for the Options directive are "None", "All",
    # or any combination of:
    #   Indexes Includes FollowSymLinks SymLinksifOwnerMatch ExecCGI MultiViews
    #
    # Note that "MultiViews" must be named *explicitly* --- "Options All"
    # doesn't give it to you.
    #
    # The Options directive is both complicated and important.  Please see
    # http://httpd.apache.org/docs/2.2/mod/core.html#options
    # for more information.
    #
    Options Indexes FollowSymLinks

    #
    # AllowOverride controls what directives may be placed in .htaccess files.
    # It can be "All", "None", or any combination of the keywords:
    #   Options FileInfo AuthConfig Limit
    #
    AllowOverride all

    #
    # Controls who can get stuff from this server.
    #

#   onlineoffline tag - don't remove
    Order Allow,Deny
    Allow from all

</Directory>

EDIT: Why it behaves this way thanks to [tntu][2]

Because of the directive Options Indexes FollowSymLinks MultiViews on LAMP (ubuntu), the url localhost/index can resolve to the file index.php, index.html. So foo would also result into foo.php, foo.html. A proper explanation can be derived from http://httpd.apache.org/docs/current/content-negotiation.html

Don't be confused to think this is url rewriting

It is because of this option in Apache Conf:

Options FollowSymLinks

Are you sure the apache.conf file and the site configuration files are the same?

From the looks of it, one's DirectoryIndex is index.php, while the other has index as the DirectoryIndex. For more information about DirectoryIndex see http://httpd.apache.org/docs/2.2/mod/mod_dir.html