Tested with Ubuntu 16.04 (Xenial) LTS and Zabbix Server 4.0 beta 1 on September 2018

Add Zabbix 4 repository (beta is version still numbered as 3.5)

echo "deb http://repo.zabbix.com/zabbix/3.5/ubuntu xenial main" | sudo tee /etc/apt/sources.list.d/zabbix4.list > /dev/null

Add the missing public key for repository with

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 082AB56BA14FE591

and update the apt package list with

apt-get update

Install the Zabbix server (if mysql has not been installed before, please note down the root password!)

apt-get install mysql-server zabbix-server-mysql zabbix-release

Secure your Mysql/MariaDB installation with

mysql_secure_installation

default answers (see below) are fine for a normal setup

Enter current password for root (enter for none): --> should be empty, just press Enter
Set root password? [Y/n] --> Y
Remove anonymous users? [Y/n] --> Y
Disallow root login remotely? [Y/n] -->  Y
Remove test database and access to it? [Y/n] --> Y
Reload privilege tables now? [Y/n] --> Y

Now login on mysql as root with the password just choosen

$ mysql -uroot -p

and create a database (and a user) for Zabbix

MariaDB [(none)]> create database zabbix character set utf8 collate utf8_bin;
MariaDB [(none)]> grant all privileges on zabbix.* to zabbix@localhost identified by '<mysql-zabbix-password>';
MariaDB [(none)]> flush privileges;
MariaDB [(none)]> quit;

Import initial schema and data for the server with:

zcat /usr/share/doc/zabbix-server-mysql/create.sql.gz | mysql -uzabbix -p zabbix

(when asked, type the <mysql-zabbix-password>)

Edit /etc/zabbix/zabbix_server.conf and set

DBPassword=<mysql-zabbix-password>

Now install Zabbix web frontend

apt-get install zabbix-frontend-php zabbix-get

Set the right timezone for you (mine is Europe/Rome)

echo -e "<Directory \"/usr/share/zabbix\">\n   php_value date.timezone Europe/Rome\n</Directory>" | sudo tee /etc/apache2/conf-available/zabbix-local.conf
sudo a2enconf zabbix-local

and restart Apache

sudo systemctl restart apache2

Now point your browser to

http://your-webserver/zabbix/

and configure the web ui and its access to the mysql database using the wizard.

Finally, when presented the Zabbix “Welcome” screen, enter the user name 'Admin' with password 'zabbix' to log in as a Zabbix superuser (then change immediately the password!)