Category: Tomcat

This post will cover installing Tomcat 9 on CentOS 8.

We’ll be using a bash script below, which is commented so you can see the steps.

We’ll install the latest stable release of Tomcat 9.x from Tomcat.org, as well as OpenJDK 8.

We’ll also update the tomcat-users.xml file to enable manager-gui and admin-gui roles and set their passwords to a random string.

Finally, we’ll create a service file and enable Tomcat to run as a systemd service.

 

As root, save the above script as tomcat9-centos8.sh and make it executable.

Run the script:

Upon completion, the GUI and Manager passwords will be displayed as below:

The random passwords will also be saved as auth.txt in the root directory.

You should now be able to access Tomcat at:

http://domain.com:8080 or http://IP:8080

This post will cover installing and configuration of Tomcat 8 on CentOS 6

Tomcat 8 implements the Servlet 3.1 and JavaServer Pages 2.3 specifications and a number of new features.

In this post, we’ll install Tomcat 8, JDK 7, configure Tomcat as a service, create a start/stop script, and (optionally) configure Tomcat to run under a non-root user.

We will also configure basic access to Tomcat Manager and take a quick look at memory management using JAVA_OPTS

Finally, we will look at running Tomcat on port 80 as well as some strategies for running Tomcat behind Apache.

I have just updated this post with Tomcat 8.0.8, the current stable release of Tomcat 8.

If you are using a different release, simply change the file names below accordingly.

To begin, we’ll need to install the Java Development Kit (JDK) 7

JDK 1.7 is the minimum JDK version for Tomcat 8.

 

You can download the latest JDK here: http://www.oracle.com/technetwork/java/javase/downloads/index.html

We’ll install JDK 7, Update 60 (7u60). The JDK is specific to 32 and 64 bit versions.

My CentOS box is 64 bit, so I’ll need: jdk-7u60-linux-x64.tar.gz.

If you are on 32 bit, you’ll need: jdk-7u60-linux-i586.tar.gz

Start by creating a new directory /usr/java:

 

Change to the /usr/java directory we created

 

Download the appropriate JDK and save it to /usr/java directory we created above.

Unpack jdk-7u60-linux-x64.tar.gz in the /usr/java directory using tar -xzf:

 

This will create the directory /usr/java/jdk1.7.0_60. This will be our JAVA_HOME.

We can now set JAVA_HOME and put Java into the path of our users.

To set it for your current session, you can issue the following from the CLI:

To set the JAVA_HOME permanently, however, we need to add below to the ~/.bash_profile of the user (in this case, root).

We can also add it /etc/profile and then source it to give to all users.

Once you have added the above to ~/.bash_profile, you should log out, then log back in and check that the JAVA_HOME is set correctly.

 

Note: If you decided to use JDK 6 rather than 7 as we did above, simply save the JDK 6 bin file to /opt (or another location), then navigate to /usr/java and issue: ‘sh /opt/jdk-6u33-linux-x64.bin’. This will create a JAVA Home of /usr/java/jdk1.6.0.33

 

We will install Tomcat 8 under /usr/share.

Switch to the /usr/share directory:

Download apache-tomcat-8.0.8.tar.gz (or the latest version) here

and save it to /usr/share

Once downloaded, you should verify the MD5 Checksum for your Tomcat download using the md5sum command.

Compare the output above to the MD5 Checksum provided next to the download link and you used above and check that it matches.

unpack the file using tar -xzf:

This will create the directory /usr/share/apache-tomcat-8.0.8

 

We will now see how to run Tomcat as a service and create a simple Start/Stop/Restart script, as well as to start Tomcat at boot.

Change to the /etc/init.d directory and create a script called ‘tomcat’ as shown below.

And here is the script we will use.

The above script is simple and contains all of the basic elements you will need to get going.

As you can see, we are simply calling the startup.sh and shutdown.sh scripts located in the Tomcat bin directory (/usr/share/apache-tomcat-8.0.8/bin).

You can adjust your script according to your needs and, in subsequent posts, we’ll look at additional examples.

CATALINA_HOME is the Tomcat home directory (/usr/share/apache-tomcat-8.0.8)

Now, set the permissions for your script to make it executable:

We now use the chkconfig utility to have Tomcat start at boot time. In my script above, I am using chkconfig: 234 20 80. 2345 are the run levels and 20 and 80 are the stop and start

priorities respectively. You can adjust as needed.

Verify it:

Now, let’s test our script.

Start Tomcat:

Stop Tomcat:

Restarting Tomcat (Must be started first):

We should review the Catalina.out log located at /usr/share/apache-tomcat-8.0.8/logs/catalina.out and check for any errors.

We can now access the Tomcat Manager page at:

http://yourdomain.com:8080 or http://yourIPaddress:8080 and we should see the Tomcat home page.

 

 

Tomcat 8 contains a number of changes that offer finer-grain roles.

For security reasons, no users or passwords are created for the Tomcat manager roles by default. In a production deployment, it is always best to remove the Manager

application.

To set roles, user name(s) and password(s), we need to configure the tomcat-users.xml file located at $CATALINA_HOME/conf/tomcat-users.xml.

In the case of our installation, $CATALINA_HOME is located at /usr/share/apache-tomcat-8.0.8.

By default the Tomcat 8 tomcat-users.xml file will have the elements between the and tags commented-out. .

New roles for Tomcat 8 offer finer-grained access and The following roles are now available:

manager-gui
manager-status
manager-jmx
manager-script
admin-gu
admin-script.

We can set the manager-gui role, for example as below

:

 

Caution should be exercised in granting multiple roles so as not to under-mind security.

 

Getting the right heap memory settings for your installation will depend on a number of factors.

For simplicity, we will set our inital heap size, Xms, and our maximum heap size, Xmx, to the same value of 128 Mb

Simliarly, there are several approaches you can take as to where and how you set your JAVA_OPTS

Again, for simplicity, we will add our JAVA_OPTS memory parameters in our Catalina.sh file.

So, open the Catalina.sh file located under /usr/share/apache-tomcat-8.0.8/bin with a text editor or vi.

Since we are using 128 Mb for both initial and maximum heap size, add the following line to Catalina.sh

 

I usually just add this in the second line of the file so it looks as so:

 

 

In our Tomcat configuration above, we are running Tomcat as Root.

For security reasons, it is always best to run services with the only those privileges that are necessary.

There are some who make a strong case that this is not required, but it’s always best to err on the side of caution.

To run Tomcat as non-root user, we need to do the following:

1. Create the group ‘tomcat’:

2. Create the user ‘tomcat’ and add this user to the tomcat group we created above.

The above will create a home directory for the user tomcat in the default user home as /home/tomcat

If we want the home directory to be elsewhere, we simply specify so using the -d switch.

The above will create the user tomcat’s home directory as /usr/share/apache-tomcat-8.0.8/tomcat

3. Change ownership of the tomcat files to the user tomcat we created above:

Note: it is possible to enhance our security still further by making certain files and directories read-only. This will not be covered in this post and care should be used when setting such

permissions.

4. Adjust the start/stop service script we created above. In our new script, we need to su to the user tomcat:

 

 

Note: the following applies when you are running Tomcat in “stand alone” mode with Tomcat running under the minimally privileged user Tomcat we created in the previous step.

 

To run services below port 1024 as a user other than root, you can add the following to your IP tables:

 

Be sure to save and restart your IP Tables.

 

As an alternative to running Tomcat on port 80, if you have Apache in front of Tomcat, you can use mod_proxy as well as ajp connector to map your domain to your Tomcat application(s) using an Apache vhost as shown below.

While Tomcat has improved it’s ‘standalone performance’, I still prefer to have Apace in front of it for a number of reasons.

In your Apache config, be sure to set KeepAlive to ‘on’. Apache tuning, of course, is a whole subject in itself…

Example 1: VHOST with mod_proxy:

 

Example 2: VHOST with ajp connector and mod_proxy:

 

In both vhost examples above, we are “mapping” the domain to Tomcat’s ROOT directory.

If we wish to map to an application such as yourdomain.com/myapp, we can add some rewrite as shown below.

This will rewrite all requests for yourdomain.com to yourdomain.com/myapp.

Example 3: VHOST with rewrite:

 

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