I did the following:
run the following command with the dir where tomcat should be created:
tomcat8-instance-create staging
than changed the ports to something unique (if you have other tomcat8 running:
nano conf/server.xml
i use the same user as the original tomcat8 so i make sure all files are owned by tomcat8
chown -R tomcat8:tomcat8 *
i copied the script tomcat8 script in /etc/init.d/
cp /etc/init.d/tomcat8 /etc/init.d/tomcat8_staging
and edited the script to make it work with my new staging env:
nano /etc/init.d/tomcat8_staging
i had to edit the following lines to:
NAME=tomcat8_staging
DEFAULT=/etc/default/tomcat8
CATALINA_BASE=/app/tomcat8/staging
CATALINA_HOME=/usr/share/tomcat8
and finally i enabled the server like this:
systemctl enable tomcat8_staging
when starting it with:
service tomcat8_staging start
i got an error about missing policy files so i created a link for that in the conf dir:
ln -s /etc/tomcat8/policy.d policy.d