Apache Invalid command Header

On a new Debian server with Apache, web site give 500 internal server error.

On checking error log, i found

[Thu Jan 04 06:44:42.483932 2018] [core:alert] [pid 27583] [client 112.133.248.19:63020] /home/user/public_html/.htaccess: Invalid command ‘Header’, perhaps misspelled or defined by a module not included in the server configuration

The error is due to Apache headers module not installed on the server.

To fix, run

a2enmod headers

Restart Apache

systemctl restart apache2

Apache