ubuntu 16.04 server zentyal install

sudo apt-get update
sudo apt-get upgrade

sudo add-apt-repository "deb http://archive.zentyal.org/zentyal 5.1 main extra"
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 10E239FF wget -q http://keys.zentyal.org/zentyal-5.1-archive.asc -O- | sudo apt-key add -


sudo apt-get update
sudo apt-get install zentyal