This is how!
Edit a .conf (in my case I have a redirects.conf) for this kind of redirects….

nano /etc/apache2/sites-enabled/redirects.conf

And add the following lines…

<VirtualHost *:80>
    ServerName example.com
    Redirect permanent / http://www.example.com/
</VirtualHost>

and naturally restart apache! 😉

service apache2 restart

Invalid command ‘AuthGroupFile’, perhaps misspelled or defined by a module not included in the server configuration

sudo a2enmod authz_groupfile && sudo service apache2 restart

Invalid command ‘RewriteEngine’, perhaps misspelled or defined by a module not included in the server configuration

sudo a2enmod rewrite && sudo service apache2 restart