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Apache Tomcat

Apache Tomcat is a web container that allows you to serve Java Servlets and JSP (Java Server Pages) web applications.

The Tomcat 6.0 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 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.

System-wide installation

To install the Tomcat server, you can enter the following command in the terminal prompt:

sudo apt-get install tomcat6

This will install a Tomcat server with just a default ROOT webapp that displays a minimal "It works" page by default.

Configuration

Tomcat configuration files can be found in /etc/tomcat6. Only a few common configuration tweaks will be described here, please see Tomcat 6.0 documentation for more.

Changing default ports

By default Tomcat 6.0 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 server on the system. This is done by changing the following lines in /etc/tomcat6/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-6, then try Sun's JVM, then try some other JVMs. If you have various JVMs installed, you can set which should be used by setting JAVA_HOME in /etc/default/tomcat6:

JAVA_HOME=/usr/lib/jvm/java-6-sun

Declaring users and roles

Usernames, passwords and roles (groups) can be defined centrally in a Servlet container. In Tomcat 6.0 this is done in the /etc/tomcat6/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.

Tomcat documentation

The tomcat6-docs package contains Tomcat 6.0 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-get install tomcat6-docs

Tomcat administration webapps

The tomcat6-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-get install tomcat6-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" in /etc/tomcat6/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" in /etc/tomcat6/tomcat-users.xml before you can access it.

For security reasons, the tomcat6 user cannot write to the /etc/tomcat6 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 tomcat6 group the necessary rights:

sudo chgrp -R tomcat6 /etc/tomcat6
sudo chmod -R g+w /etc/tomcat6

Tomcat examples webapps

The tomcat6-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-get install tomcat6-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 6.0 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-get install tomcat6-user

Creating a private instance

You can create a private instance directory by entering the following command in the terminal prompt:

tomcat6-instance-create my-instance

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):

my-instance/bin/startup.sh

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):

my-instance/bin/shutdown.sh

References

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