This is not a complete installation, but may help people get started while highlighting a couple of issues:
Go to DigitalOcean or any other server provider (including your own), and install the latest Ubuntu (Debian, etc):
#paste one line
apt update; apt-get -y install joe tree unzip fastjar tomcat9 tomcat9-admin postgresql #postgis
#paste one line
apt-get -y dist-upgrade; apt-get -y autoremove; sync; reboot
#log in again, then paste the following all the way to starting tomcat again
systemctl stop tomcat9
ed /etc/tomcat9/tomcat-users.xml <<EOF
/manager-gui
/-->
a
<role rolename="manager-gui"/>
<role rolename="admin-gui"/>
<user username="tomcat" password="s3cret" roles="manager-gui,admin-gui"/>
.
wq
EOF
wget https://netcologne.dl.sourceforge.net/project/cmdbuild/3.2/cmdbuild-3.2.war
mkdir cmdbuild; ( cd cmdbuild; jar -xf ../cmdbuild-3.2.war )
mv cmdbuild /var/lib/tomcat9/webapps/
( cd /var/lib/tomcat9; mkdir conf/cmdbuild; chown -R tomcat conf/cmdbuild webapps/cmdbuild )
# Systemctl sandboxes Tomcat, therefore saving the configuration file will fail unless following is done:
ed tomcat9.service << EOF
/ReadWritePaths
a
ReadWritePaths=/var/lib/tomcat9/conf/cmdbuild/
.
wq
EOF
systemctl daemon-reload
# Documentation says Cmdbuild uses tomcat-jdbc, this is not actually the case
wget https://jdbc.postgresql.org/download/postgresql-42.2.10.jar
mv postgresql-42.2.10.jar /usr/share/java
( cd /usr/share/tomcat9/lib; ln -s ../../java/postgresql-42.2.10.jar )
su - postgres -c psql <<EOF
alter role postgres password 'postgres' login;
EOF
#rm /var/log/tomcat9/*
systemctl start tomcat9
Willing to work on developing this further (eg, GIS installation).