SHELL

restart apache

sudo systemctl restart apache2
# or
sudo service apache2 restart

linux apache restart

sudo service apache2 start
sudo service apache2 restart
sudo service apache2 stop

OR 

sudo /etc/init.d/apache2 start
sudo /etc/init.d/apache2 restart
sudo /etc/init.d/apache2 stop

apache restart

# CentOS/RedHat
sudo service httpd restart

# Debian/Ubuntu
sudo service apache2 restart

apache start stop restart

sudo service apache2 restart
sudo service apache2 stop
sudo service apache2 start