Quick and easy method to install Webmin manager on Ubuntu Server.

sudo -i
echo "deb https://download.webmin.com/download/repository sarge contrib" >> /etc/apt/sources.list
cd /root
wget https://download.webmin.com/jcameron-key.asc
apt-key add jcameron-key.asc
apt-get install apt-transport-https
apt-get update
apt-get install webmin