Apache Tomcat is a web container that allows you to serve Java Servlets and JSP (Java Server Pages) web applications.
Ubuntu has supported packages for both Tomcat 6 and 7. Tomcat 6 is the legacy version, and Tomcat 7 is the current version where new features are implemented. Both are considered stable. This guide will focus on Tomcat 7, but most configuration details are valid for both versions.
The Tomcat packages in Ubuntu support two different ways of running Tomcat. You can install them as a classic unique system-wide instance, that will be started at boot time will run as the tomcat7 (or tomcat6) unprivileged user. But you can also deploy private instances that will run with your own user rights, and that you should start and stop by yourself. This second way is particularly useful in a development server context where multiple users need to test on their own private Tomcat instances.
To install the Tomcat server, you can enter the following command in the terminal prompt:
sudo apt install tomcat7
This will install a Tomcat server with just a default ROOT webapp that displays a minimal "It works" page by default.
Tomcat configuration files can be found in /etc/tomcat7. Only a few common configuration tweaks will be described here, please see Tomcat 7.0 documentation for more.
Changing default ports
By default Tomcat runs a HTTP connector on port 8080 and an AJP connector on port 8009. You might want to change those default ports to avoid conflict with another application on the system. This is done by changing the following lines in /etc/tomcat7/server.xml:
<Connector port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" /> ... <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" />
Changing JVM used
By default Tomcat will run preferably with OpenJDK JVMs, then try the Sun JVMs, then try some other JVMs. You can force Tomcat to use a specific JVM by setting JAVA_HOME in /etc/default/tomcat7:
Declaring users and roles
Usernames, passwords and roles (groups) can be defined centrally in a Servlet container. This is done in the /etc/tomcat7/tomcat-users.xml file:
<role rolename="admin"/> <user username="tomcat" password="s3cret" roles="admin"/>
Using Tomcat standard webapps
Tomcat is shipped with webapps that you can install for documentation, administration or demo purposes.
The tomcat7-docs package contains Tomcat documentation, packaged as a webapp that you can access by default at http://yourserver:8080/docs. You can install it by entering the following command in the terminal prompt:
sudo apt install tomcat7-docs
Tomcat administration webapps
The tomcat7-admin package contains two webapps that can be used to administer the Tomcat server using a web interface. You can install them by entering the following command in the terminal prompt:
sudo apt install tomcat7-admin
The first one is the manager webapp, which you can access by default at http://yourserver:8080/manager/html. It is primarily used to get server status and restart webapps.
Access to the manager application is protected by default: you need to define a user with the role "manager-gui" in /etc/tomcat7/tomcat-users.xml before you can access it.
The second one is the host-manager webapp, which you can access by default at http://yourserver:8080/host-manager/html. It can be used to create virtual hosts dynamically.
Access to the host-manager application is also protected by default: you need to define a user with the role "admin-gui" in /etc/tomcat7/tomcat-users.xml before you can access it.
For security reasons, the tomcat7 user cannot write to the /etc/tomcat7 directory by default. Some features in these admin webapps (application deployment, virtual host creation) need write access to that directory. If you want to use these features execute the following, to give users in the tomcat7 group the necessary rights:
sudo chgrp -R tomcat7 /etc/tomcat7 sudo chmod -R g+w /etc/tomcat7
Tomcat examples webapps
The tomcat7-examples package contains two webapps that can be used to test or demonstrate Servlets and JSP features, which you can access them by default at http://yourserver:8080/examples. You can install them by entering the following command in the terminal prompt:
sudo apt install tomcat7-examples
Using private instances
Tomcat is heavily used in development and testing scenarios where using a single system-wide instance doesn't meet the requirements of multiple users on a single system. The Tomcat packages in Ubuntu come with tools to help deploy your own user-oriented instances, allowing every user on a system to run (without root rights) separate private instances while still using the system-installed libraries.
It is possible to run the system-wide instance and the private instances in parallel, as long as they do not use the same TCP ports.
Installing private instance support
You can install everything necessary to run private instances by entering the following command in the terminal prompt:
sudo apt install tomcat7-user
Creating a private instance
You can create a private instance directory by entering the following command in the terminal prompt:
This will create a new my-instance directory with all the necessary subdirectories and scripts. You can for example install your common libraries in the lib/ subdirectory and deploy your webapps in the webapps/ subdirectory. No webapps are deployed by default.
Configuring your private instance
You will find the classic Tomcat configuration files for your private instance in the conf/ subdirectory. You should for example certainly edit the conf/server.xml file to change the default ports used by your private Tomcat instance to avoid conflict with other instances that might be running.
Starting/stopping your private instance
You can start your private instance by entering the following command in the terminal prompt (supposing your instance is located in the my-instance directory):
You should check the logs/ subdirectory for any error. If you have a java.net.BindException: Address already in use<null>:8080 error, it means that the port you're using is already taken and that you should change it.
You can stop your instance by entering the following command in the terminal prompt (supposing your instance is located in the my-instance directory):