Installation process / Cheat sheet (example for Debian based distros):

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Update apt repositories and upgrade:
sudo apt update
sudo apt upgrade

Install MySQL:
apt-get install mysql-server

Install JDK:
apt-get install default-jdk

Install Java Database Connector (JDBC):
wget http://dev.mysql.com/get/Downloads/Connector-J/mysql-connector-java-5.1.44.zip -O /tmp/mysql-connector-java.zip
unzip /tmp/mysql-connector-java.zip -d /tmp && \
cp /tmp/mysql-connector-java-5.1.44/mysql-connector-java-5.1.44-bin.jar /opt/tomcat/webapps/activiti-rest/WEB-INF/lib/
cp /tmp/mysql-connector-java-5.1.44/mysql-connector-java-5.1.44-bin.jar /opt/tomcat/webapps/activiti-explorer/WEB-INF/lib/
rm -rf /tmp/mysql-connector-java.zip /tmp/mysql-connector-java-5.1.44

Install Activiti 5:
sudo groupadd tomcat
sudo useradd -s /bin/false -g tomcat -d /opt/tomcat tomcat
cd /tmp
curl -O http://mirrors.ae-online.de/apache/tomcat/tomcat-8/v8.5.23/bin/apache-tomcat-8.5.23.tar.gz
sudo mkdir /opt/tomcat
sudo tar xzvf apache-tomcat-8.5.23.tar.gz -C /opt/tomcat --strip-components=1
cd /opt/tomcat
sudo chgrp -R tomcat /opt/tomcat
sudo chmod -R g+r conf
sudo chmod g+x conf
sudo chown -R tomcat webapps/ work/ temp/ logs/
update-java-alternatives -l
nano /etc/systemd/system/tomcat.service

Paste following to tomcat.service:

[Unit]

Description=Apache Tomcat Web Application Container
After=network.target

[Service]

Type=forking
Environment=JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre
Environment=CATALINA_PID=/opt/tomcat/temp/tomcat.pid
Environment=CATALINA_HOME=/opt/tomcat
Environment=CATALINA_BASE=/opt/tomcat
Environment='CATALINA_OPTS=-Xms512M -Xmx1024M -server -XX:+UseParallelGC'
Environment='JAVA_OPTS=-Djava.awt.headless=true -Djava.security.egd=file:/dev/./urandom'
ExecStart=/opt/tomcat/bin/startup.sh
ExecStop=/opt/tomcat/bin/shutdown.sh
User=tomcat
Group=tomcat
UMask=0007
RestartSec=10
Restart=always

[Install]

WantedBy=multi-user.target
cd /tmp
wget https://github.com/Activiti/Activiti/releases/download/activiti-5.22.0/activiti-5.22.0.zip -O /tmp/activiti.zip
unzip /tmp/activiti.zip -d /opt/activiti
unzip /opt/activiti/activiti-5.22.0/wars/activiti-explorer.war -d /opt/tomcat/webapps/activiti-explorer
unzip /opt/activiti/activiti-5.22.0/wars/activiti-rest.war -d /opt/tomcat/webapps/activiti-rest
rm -f /tmp/activiti.zip

Download project directory Workflowmanager from GitHub:
Download with browser as .zip or use git clone

Configure MySQL:
mysql create database activititest;
CREATE USER 'activiti'@'localhost' IDENTIFIED BY 'activiti';
GRANT ALL PRIVILEGES ON activititest . * TO 'activiti'@'localhost';

Edit db.properies of Activiti to use MySQL as Activiti Storage, for example by inserting:
db=activititest
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/activititest
jdbc.username=activiti
jdbc.password=activiti

Create Users “juice”,”puree” and “pieces” in activiti: