Apache - Invalid command 'Header', perhaps misspelled or defined by a module not included in the server configuration

Apache - Invalid command 'Header', perhaps misspelled or defined by a module not included in the server configuration

Ошибка

Invalid command 'Header', perhaps misspelled or defined by a module not included in the server configuration 

означает, что не подключен модуль mod_headers для Apache.

Для Debian/Ubuntu решается командами:

# a2enmod headers
Enabling module headers.
To activate the new configuration, you need to run:
 service apache2 restart
# /etc/init.d/apache2 restart

Проверяем модуль:

# apachectl -M | grep head
headers_module (shared)
Syntax OK