3.12. Installing Jenkins as a Windows Service

If you are running a production installation of Jenkins on a Windows box, it is essential to have it running as a Windows service. This way, Jenkins will automatically start whenever the server reboots, and can be managed using the standard Windows administration tools.

One of the advantages of running Jenkins on an application server such as Tomcat is that it is generally fairly easy to configure these servers to run as a Windows service. However, it is also fairly easy to install Jenkins as a service, without having to install Tomcat.

Jenkins has a very convenient feature designed to make it easy to install Jenkins as a Windows servers. There is currently no graphical installer that does this for you, but you get the next best thing—a web-based graphical installer.

First, you need to start the Jenkins server on your target machine. The simplest approach is to run Jenkins using Java Web Start (see Figure 3.4, “Starting Jenkins using Java Web Start” ). Alternatively, you can do this by downloading Jenkins and running it from the command line, as we discussed earlier:

			java -jar jenkins.war

This second option is useful if the default Jenkins port (8080) is already being used by another application. It doesn’t actually matter which port you use—you can change this later.

Starting Jenkins using Java Web Start

Figure 3.4. Starting Jenkins using Java Web Start

Once you have Jenkins running, connect to this server and go to the Manage Jenkins screen. Here you will find an Install as Windows Service button. This will create a Jenkins service on the server that will automatically start and stop Jenkins in an orderly manner (see Figure 3.5, “Installing Jenkins as a Windows service” ).

Jenkins will prompt you for an installation directory. This will be the Jenkins home directory ( JENKINS_HOME ). The default value is the default JENKINS_HOME value: a directory called .jenkins in the current user’s home directory. This is often not a good choice for a Windows installation. When running Jenkins on Windows XP, you should avoid installing your Jenkins home directory anywhere near your C:\\Documents And Settings directory—not only is it a ridiculously long name, the spaces can wreak havoc with your Ant and Maven builds and any tests using classpath-based resources. It is much better to use a short and sensible name such as C:\Jenkins . The Vista and Windows 7 home directory paths like C:\Users\john will also work fine.

Installing Jenkins as a Windows service

Figure 3.5. Installing Jenkins as a Windows service

A short home directory path is sometimes required for other reasons, too. On many versions of Windows (Windows XP, Windows Server 2003, etc.), file path lengths are limited to around 260 characters. If you combine a nested Jenkins work directory and a deep class path, you can often overrun this, which will result in very obscure build errors. To minimize the risks of over-running the Windows file path limits, you need to redefine the JENKINS_HOME environment variable to point to a shorter path, as we discussed above.

This approach won’t always work with Windows Vista or Windows 7. An alternative strategy is to use the jenkins.exe program that the Web Start installation process will have installed in the directory you specified above. Open the command line prompt as an administrator (right-click, “Run as administrator”) and run the jenkins.exe executable with the install option:

			jenkins.exe install

This basic installation will work fine in a simple context, but you will often need to fine-tune your service. For example, by default, the Jenkins service will be running under the local System account. However, if you are using Maven, Jenkins will need an .m2 directory and a settings.xml file in the home directory. Similarly, if you are using Groovy, you might need a .groovy/lib directory. And so on. To allow this, and to make testing your Jenkins install easier, make sure you run this service under a real user account with the correct development environment set up (see Figure 3.6, “Configuring the Jenkins Windows Service” ). Alternatively, run the application as the system user, but use the System Information page in Jenkins to check the /jenkins-guide-complet directory, and place any files that must be placed in the user home directory here.

Configuring the Jenkins Windows Service

Figure 3.6. Configuring the Jenkins Windows Service

You configure the finer details of the Jenkins service in a file called jenkins.xml , in the same directory as your jenkins.war file. Here you can configure (or reconfigure) ports, JVM options, an the Jenkins work directory. In the following example, we give Jenkins a bit more memory and get it to run on port 8081:

			<description>This service runs the Jenkins continuous integration system
			<env name="JENKINS_HOME" value="D:\jenkins" />
			<arguments>-Xrs -Xmx512m
			-jar "%BASE%\jenkins.war" --httpPort=8081

Finally, if you need to uninstall the Jenkins service, you can do one of two things. The simplest is to run the Jenkins executable with the uninstall option:

			jenkins.exe uninstall

The other option is to use the Windows service tool sc :

			sc delete jenkins