reinstal apache2 ubuntu

sudo apt-get --purge remove apache2
sudo apt-get autoremove
sudo apt-get install apache2
sudo /etc/init.d/apache2 restart

sudo apt-get install apache2

#stop the apache2 service 
$ sudo systemctl stop apache2 

#remove apache2 packages
$ sudo apt-get purge apache2 apache2-utils apache2-bin apache2.2-common

# cleanup
$ sudo apt-get autoremove

# check if the apache has been removed:
#1- following command line should return a blank line
$ which apache2   
# 2- following command line should return apache2: Failed to start apache2.service: Unit apache2.service not found.
$ sudo systemctl start apache2