Double the Tomcat: Run Two Instances on One Server

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Creating a Custom Unit File for a Second Instance of Apache Tomcat

Need to run multiple instances of Tomcat on the same machine? You can set up a second instance by duplicating the configuration and customizing key parameters to avoid conflicts with the first instance.

Step-by-Step Procedure

1. Duplicate the Tomcat Installation

Start by copying the existing Tomcat directory (typically /opt/tomcat):

# cp -r /opt/tomcat /opt/tomcat-second

This creates an independent folder for the second instance, which you can configure separately.

2. Customize Ports and Settings

Edit /opt/tomcat-second/conf/server.xml and modify ports to avoid clashes with the default instance. For example:

  • HTTP Connector: Change port="8080" to port="8081"
  • Shutdown Port: Change port="8005" to something like port="8006"
  • AJP Connector: Change port="8009" to port="8010"

3. Create a Custom systemd Unit File

Duplicate the existing systemd unit file or create a new one:

# cp /etc/systemd/system/tomcat.service /etc/systemd/system/tomcat-second.service

Edit the tomcat-second.service file and adjust key sections:

[Unit]
Description=Apache Tomcat Second Instance
After=network.target

[Service]
Type=forking
User=tomcat
Group=tomcat
Environment=CATALINA_PID=/opt/tomcat-second/temp/tomcat.pid
Environment=CATALINA_HOME=/opt/tomcat-second
Environment=CATALINA_BASE=/opt/tomcat-second
ExecStart=/opt/tomcat-second/bin/startup.sh
ExecStop=/opt/tomcat-second/bin/shutdown.sh
Restart=on-failure

[Install]
WantedBy=multi-user.target
  • CATALINA_BASE: Points to the second Tomcat directory
  • CATALINA_PID: Unique PID file to prevent collision
  • Startup/Shutdown Scripts: Use the ones inside /opt/tomcat-second/bin

4. Enable and Start the Second Instance

Reload systemd so it picks up the new service:

# systemctl daemon-reload
# systemctl enable tomcat-second.service
# systemctl start tomcat-second.service

5. Verify the Status and Access

Check the status of the second instance:

# systemctl status tomcat-second.service

Then open a browser and visit: http://yourserver:8081

6. Allow Port in Firewall (If Applicable)

If you're using a firewall, don't forget to open the new port:

# firewall-cmd --permanent --add-port=8081/tcp
# firewall-cmd --reload

Optional: SELinux Adjustment (if enforced)

If SELinux is enforcing and you face binding issues, you can label the port appropriately:

# semanage port -a -t http_port_t -p tcp 8081

Done!

You now have a fully working second instance of Apache Tomcat running as a systemd service, independently managed from the original instance.

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