Install Apache Tomcat 8 on Ubuntu 16.04

Install Java

Create Tomcat User

sudo groupadd tomcat
sudo useradd -s /bin/false -g tomcat -d /opt/tomcat tomcat

Install Tomcat

sudo mkdir /opt/tomcat
wget http://apache.mirrors.ionfish.org/tomcat/tomcat-8/v8.5.5/bin/apache-tomcat-8.5.5.tar.gz

Update Permissions

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/

Create a systemd Service File

sudo update-java-alternatives -l
Output
java-1.8.0-openjdk-amd64       1081       /usr/lib/jvm/java-1.8.0-openjdk-amd64
sudo nano /etc/systemd/system/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
sudo systemctl daemon-reload
sudo systemctl start tomcat
sudo systemctl status tomcat

Configure Tomcat Web Management Interface

sudo nano /opt/tomcat/conf/tomcat-users.xml
<tomcat-users . . .>
    <user username="admin" password="password" roles="manager-gui,admin-gui"/>
</tomcat-users>

For the Manager app, type:

sudo nano /opt/tomcat/webapps/manager/META-INF/context.xml

For the Host Manager app, type:

sudo nano /opt/tomcat/webapps/host-manager/META-INF/context.xml
<Context antiResourceLocking="false" privileged="true" >
  <!--<Valve className="org.apache.catalina.valves.RemoteAddrValve"
         allow="127\.\d+\.\d+\.\d+|::1|0:0:0:0:0:0:0:1" />-->
</Context>
sudo systemctl restart tomcat

Access the Web Interface

http://server_domain_or_IP:8080

References
https://www.digitalocean.com/community/tutorials/how-to-install-apache-tomcat-8-on-ubuntu-16-04