tomcat 8 will not start after initial install

I had the same problem, fixed it by:

1. giving tomcat user ownership of the whole tomcat directory:

   cd /opt && sudo chown -R tomcat tomcat/
   

2. and commenting out below line in /etc/systemd/system/tomcat.service:

   Environment='CATALINA_OPTS=-Xms512M -Xmx1024M -server -XX:+UseParallelGC'
   

Since you installed Java in a non defalt location you need to tell tomcat where to find it.

In the unit file you posted JAVA_HOME is set to /usr/lib/jvm/jre but in the section about the java installation JAVA_HOME is /opt/jdk1.8.0_60.

If you set JAVA_HOME in the tomcat systemd unit file I believe it will work.

Also the unit file specifies user tomcat. But when you start it manually you start it as root. The problem is likely that tomcat attempts to open a privileged port. Does the start script start tomcat as root? Or does it start processes as user tomcat? Removing the user and group from the unit file should trigger the same behaviour of your command line attempt.