At work we rely heavily on continuous integration and deployment to help us deliver lots of code into production and staging environments quickly. In a typical day, we’ll make something like 15 deployments to at least one or two of our projects.

The software we use to manage this is crucial to us, as programmers, because it makes our lives much easier. Instead of manually running large test suites against remote servers, we just let our CI system run the tests as soon as we push our code to GitHub, and once our tests pass, deploy the code live :)

Today I’m setting up a new Jenkins CI server for work, to move off our old Hudson server, so I figured this would be a good time to blog about the process, as it’s so extremely helpful to us that I can’t imagine ever programming without it again.

For the rest of this tutorial, I expect that you:

• Are using Ubuntu server or Debian server as your operating system.
• Are familiar with the Linux command line.
• Know what continuous integration and continuous deployment are.
• Have some code to test deploy.

Installing Jenkins

Installing Jenkins is ridiculously easy on Debian systems:

$ wget -q -O - http://pkg.jenkins-ci.org/debian/jenkins-ci.org.key | sudo apt-key add -
$ sudo echo "deb http://pkg.jenkins-ci.org/debian binary/" > /etc/apt/sources.list.d/jenkins.list
$ sudo aptitude -y update
$ sudo aptitude -y install jenkins

Congratulations, you now have Jenkins running! To visit your new Jenkins instance, just visit http://youserverip:8080/. If you want to update it, you can do so with the rest of the system (via aptitude -y update; aptitude -y safe-upgrade).

Configure a HTTP Proxy With NGINX

Since Jenkins by default runs on port 8080, I like setting up an HTTP proxy so to that I can access it on port 80. My weapon of choice for proxying is NGINX, so let’s set that up now:

$ sudo aptitude -y install nginx
$ cd /etc/nginx/sites-available
$ sudo rm default
$ sudo cat > jenkins
upstream app_server {
    server 127.0.0.1:8080 fail_timeout=0;
}

server {
    listen 80;
    listen [::]:80 default ipv6only=on;
    server_name ci.yourcompany.com;

    location / {
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_redirect off;

        if (!-f $request_filename) {
            proxy_pass http://app_server;
            break;
        }
    }
}
^D # Hit CTRL + D to finish writing the file
$ sudo ln -s /etc/nginx/sites-available/jenkins /etc/nginx/sites-enabled/
$ sudo service nginx restart

Now you should be able to visit http://ci.yourcompany.com/ and see your Jenkins instance on the default HTTP port 80.

Secure Jenkins

Jenkins has built-in user account management, which makes it easy to lock your interface down. Below, we’ll create two accounts: admin and rdegges. admin will have full permissions to the projects, and rdegges will only be able to view project statuses, but not update any settings or make project changes. Changing the security rules for your environment are pretty intuitive, once you see how it works:

1. Click the Manage Jenkins link on the left side of your page.
2. Click the Configure System link.
3. Check the box labeled Enable security.
4. Select the bubble labeled Jenkins’s own user database.
5. Select the bubble labeled Matrix-based security.
6. Enter admin in the text box labeled User/group to add then click Add.
7. Enter rdegges in the text box labeled User/group to add then click Add.
8. For admin, check all the square boxes that run horizontally. This allows the admin user to do anything.
9. For rdegges, check only the square boxes labeled Read.
10. Scroll to the bottom of the page and click the Save button.

If you did everything properly, your page should look something like this:

Now that you’ve applied some rules, you need to actually create the two user accounts you supplied rules for. On the main Jenkins page, click the Create an account link, and create two accounts–one for admin, and one for rdegges. Note that when you log into each of these accounts, they have the permissions you supplied earlier. If you want to change permissions, just log in as the admin user, and go through the same steps above.

Install and Configure Git

The core functionality of Jenkins is to use some form of version control software (I use Git) to check out some release of code, and then do stuff with it. Below, we’ll setup Git on our server, and in Jenkins, so that we can check out all of our Git projects.

Firstly, you’ll want to run the following commands on your server to install Git. You’ll obviously need to make changes to this code for your environment:

$ sudo aptitude -y install git
$ sudo su - jenkins
$ git config --global user.name "Jenkins CI"
$ git config --global user.email "ci@yourcompany.com"
$ ssh-keygen -t rsa -C "ci@yourcompany.com" # Use all the default options, don't specify
                                          # a password.
$ cat .ssh/id_rsa.pub # Grant this SSH key access to your Git repositories.

# If you're using github, you'll also want to do:
$ ssh git@github.com
# And accept the connection so that you add github.com to your known_hosts file.

Once you’ve done all that, all you need to do is follow the next few steps in the web panel:

1. From the main page, click the Manage Jenkins link.
2. Click the Manage Plugins link.
3. Click the Advanced tab.
4. Click the Check Now button.
5. Click the Back to Dashboard link.
6. Click the Manage Jenkins link.
7. Click the Manage Plugins link.
8. Click the Available tab.
9. Check the box labeled Git Plugin (it’s towards the bottom of the page).
10. Scroll to the bottom of the page and click the Install button.
11. Once the plugin has been installed, click the Restart When No Jobs Are Running button.

You’ve now got Git ready to roll.

Configure a Project

In this step we’ll configure Jenkins to check out the latest copy of our project’s code, run the test suite, and then deploy our code live into production. It’s a lot easier than it sounds, let’s take a look:

1. Click the New Job link.
2. Enter your project’s name into the Job name box.
3. Select the Build a free-style software project link.
4. Click the OK button.
5. Under the Source Code Management section, select the bubble next to Git.
6. Enter the URL of your Git repository. This is usually something like: git://github.com/rdegges/django_project.git.
7. Under the Build Triggers section, select the box labeled Poll SCM.
8. In the Schedule box that appears, enter * * * * * (don’t include the quotes). This instructs Jenkins to check your Git repository for changes every minute. If you want to change the frequency, feel free to do so using crontab format.
9. Under the Build section, click the Add Build Step button, then select Execute shell.
10. In the Command box that appears, enter your commands to build, test, and deploy your software.
11. Scroll to the bottom of the page and click the Save button.

That’s it! Jenkins will now automatically poll your Git repository every minute for changes. If any code was changed, it will check out the latest version of your code, then execute the commands you specified as build steps–which should be testing and deploying your code.

If you go back to the main page, you’ll be able to view the status of all your projects, and click through to see detailed information about builds, errors, and lots of other neat stuff.

RTFM

Obviously, a 5 minute walk-through is no excuse for not learning how to use Jenkins properly. If you want to learn how to make the best use of Jenkins, and experiment with the hundreds of awesome plugins that it has, be sure to read the official documentation.