Install Jenkins on Ubuntu Server

10 April 2021

This article is for those looking for a detailed and straightforward guide on installing Jenkins on Ubuntu Server.

Jenkins is an open-source Java software system designed to provide a continuous software integration process.

In this guide, we will consider the case when you already have a server with the Ubuntu Server 20.04 LTS operating system installed on it.

You can read more about how to install Ubuntu Server 20.04 LTS in my guide “Install Ubuntu Server 20.04 LTS”.

In addition, OpenSSH must be installed on the server, and port 22 must be open in order to be able to connect to the server using the SSH protocol.

To install OpenSSH on a server, you can use the command:

sudo apt install openssh-server

If you plan to connect to the server using the Windows operating system, you can use PuTTY or MobaXterm.

This guide describes how to connect to a server using the iTerm2 terminal emulator installed on the macOS operating system.

Please note that you will need to open the following TCP ports to access your server:

• TCP port 80 - to receive a free cryptographic certificate through the Let’s Encrypt CA.
• TCP port 443 - to access Jenkins web interface.

We connect to the server on which you plan to install Jenkins.

To obtain and subsequently renew a free SSL certificate, we will use the Let’s Encrypt certification authority, as well as the Certbot software client, which is designed to make it as easy as possible to obtain and renew a certificate through the Let’s Encrypt certification authority.

Update the local package index to the latest changes in the repositories using the command:

sudo apt update

Now we will install the packages required for Jenkins to work using the command:

sudo apt install -y apache2 apt-transport-https certbot python3-certbot-apache openjdk-11-jdk

Note that this tutorial will use Apache as the webserver.

Please note, you can check the supported Java versions by following the link.

Many programs written using Java use the “JAVA_HOME” environment variable to determine where Java is installed. Therefore, you need to define this variable and assign it a value containing the path to the Java installation location.

Let’s define the path to the Java installation location using the command:

sudo update-alternatives --config java

In this example, the path to the Java installation location looks like this:

/usr/lib/jvm/java-11-openjdk-amd64/bin/

In order to define an environment variable and assign a value to it, you need to make changes to the “environment” file by opening it in a text editor using the command:

sudo vim /etc/environment

Press the “i” button to switch to edit mode, then at the end of the file define a new variable “JAVA_HOME” and assign it a value containing the path to the Java installation location obtained earlier.

JAVA_HOME="/usr/lib/jvm/java-11-openjdk-amd64/bin/"

Please note that the path to the Java installation location must be specified up to and including the “bin” folder.

Now press the “Esc” button to exit edit mode, and then type “:x” and press the “Enter” button to save your changes and exit the editor.

Next, you need to apply the changes made to the current session using the command:

source /etc/environment

Now let’s make sure that the environment variable has the correct value using the command:

echo $JAVA_HOME

Based on the message received, the environment variable has the correct value.

Let’s configure Apache for further work with the Jenkins dashboard.

We enable the Apache webserver module called “headers” using the command:

sudo a2enmod headers

Note that the “headers” module can be used to add more specific “Cache-Control” parameters.

We enable the Apache webserver module called “proxy_http” using the command:

sudo a2enmod proxy_http

Please note that the “proxy_http” module acts like a proxy server for the HTTP and HTTPS protocols.

We enable the Apache webserver module called “rewrite” using the command:

sudo a2enmod rewrite

Note that the “rewrite” module is one of the most commonly used modules in the Apache webserver and provides a flexible and powerful way to manipulate URLs.

Now you need to create two virtual host files (called a block in Nginx), which Jenkins will work with in the future.

Two virtual host files will be required to provide access to Jenkins over HTTPS, as well as to enable Jenkins to be used at https://jenkins.heyvaldemar.net, without specifying port 8080 in the browser address bar.

In this tutorial, you will use the jenkins.heyvaldemar.net subdomain to access Jenkins from the Internet. You will need to specify your domain or subdomain by which your Jenkins will be accessible from the Internet.

Let’s create the first virtual host file using a text editor using the command:

sudo vim /etc/apache2/sites-available/jenkins.heyvaldemar.net.conf

Hit the “i” button to go into edit mode, then insert the following configuration for the webserver to work.

In this tutorial, you will use the jenkins.heyvaldemar.net subdomain to access Jenkins from the Internet. You will need to specify your domain or subdomain by which your Jenkins will be accessible from the Internet.

Now press the “Esc” button to exit edit mode, and then type “:x” and press the “Enter” button to save your changes and exit the editor.

Let’s create a second virtual host file using a text editor using the command:

sudo vim /etc/apache2/sites-available/jenkins.heyvaldemar.net-ssl.conf

Hit the “i” button to go into edit mode, then insert the following configuration for the webserver to work.

In this tutorial, you will use the jenkins.heyvaldemar.net subdomain to access Jenkins from the Internet. You will need to specify your domain or subdomain by which your Jenkins will be accessible from the Internet.

Now press the “Esc” button to exit edit mode, and then type “:x” and press the “Enter” button to save your changes and exit the editor.

We activate the first virtual host using the command:

sudo a2ensite jenkins.heyvaldemar.net.conf

We activate the second virtual host using the command:

sudo a2ensite jenkins.heyvaldemar.net-ssl.conf

Deactivate the default virtual host using the command:

sudo a2dissite 000-default.conf

Verify that there are no errors in the syntax of the new Apache config file using the command:

sudo apache2ctl configtest

Restart Apache to apply the changes, using the command:

sudo systemctl restart apache2

Let’s check that Apache has started successfully using the command:

sudo systemctl status apache2

Now, in order to increase the security level of the webserver, you need to obtain a cryptographic certificate for the domain or subdomain, through which the Jenkins dashboard will be accessible from the Internet.

To obtain and subsequently renew a free SSL certificate, we will use the Let’s Encrypt certification authority, as well as the Certbot software client, which is designed to make it as easy as possible to obtain and renew a certificate through the Let’s Encrypt certification authority.

In this tutorial, you will use the jenkins.heyvaldemar.net subdomain to access Jenkins from the Internet. You will need to specify your domain or subdomain by which your Jenkins will be accessible from the Internet.

Let’s request a cryptographic certificate using the command:

sudo certbot --apache -d jenkins.heyvaldemar.net

Next, we specify the email address to which Let’s Encrypt will send notifications about the expiration of the cryptographic certificate and press the “Enter” button.

The next step is to read and accept the terms of use of the services provided.

Press the button “a”, then “Enter”, if you agree with the terms of use of the services provided.

The next step is to choose: do you want to share the above email address with the Electronic Frontier Foundation in order to receive newsletters.

Press the “n” button, then “Enter”.

At the next stage, you need to choose: do you want the parameters to be automatically added to the Apache configuration file for automatically redirecting HTTP traffic to HTTPS.

Press the button “2”, then “Enter”.

Please note that cryptographic certificates obtained through Let’s Encrypt CA are valid for ninety days. Certbot automatically adds a script to renew the certificate to the task scheduler, and the script runs twice a day, automatically renewing any cryptographic certificate that expires within thirty days.

You can check the functionality of the cryptographic certificate renewal process using the command:

sudo certbot renew --dry-run

Now let’s add the official Jenkins key using the command:

wget -q -O - https://pkg.jenkins.io/debian-stable/jenkins.io.key | sudo apt-key add -

Next, we connect the Jenkins repository using the command:

sudo sh -c 'echo deb http://pkg.jenkins.io/debian-stable binary/ > /etc/apt/sources.list.d/jenkins.list'

Update the local package index to the latest changes in the repositories using the command:

sudo apt update

Now let’s install Jenkins using the command:

sudo apt install -y jenkins

Now you need to make changes to the Jenkins configuration file by opening it in a text editor using the command:

sudo vim /etc/default/jenkins

Hit the “i” button to enter edit mode, find the line JENKINS_ARGS=”–webroot=/var/cache/$NAME/war –httpPort=$HTTP_PORT” and add the parameter –httpListenAddress=127.0.0.1.

Now press the “Esc” button to exit edit mode, and then type “:x” and press the “Enter” button to save your changes and exit the editor.

Restart Jenkins to apply the changes made using the command:

sudo systemctl restart jenkins

Let’s check that Jenkins has started successfully using the command:

sudo systemctl status jenkins

Now you need to get the password that you need to unlock Jenkins.

You can get the password using the command:

sudo cat /var/lib/jenkins/secrets/initialAdminPassword

Save the resulting password as you will need it in the next step.

To continue the Jenkins installation process, you need to go from the workstation to the link https://jenkins.heyvaldemar.net, where jenkins.heyvaldemar.net is the name of my server. Accordingly, you need to provide the name or IP address of your Jenkins server.

Next, you need to provide a password to unlock Jenkins.

In the “Administrator password” field, specify the previously received password to unlock Jenkins and click on the “Continue” button.

Now you can choose which plugins to install for Jenkins.

In this tutorial, we will be looking at installing the suggested plugins for Jenkins.

Click on the “Install suggested plugins” button.

The process of installing plugins has begun.

At the next step, you need to specify: login, password, name, and email address to create a Jenkins administrator account.

Click on the “Save and Continue” button.

In the “Jenkins URL” field, specify the domain or subdomain by which your Jenkins is accessible from the Internet.

This tutorial will use the jenkins.heyvaldemar.net subdomain to access Jenkins from the Internet. You will need to specify your domain or subdomain by which your Jenkins will be accessible from the Internet.

Click on the “Save and Finish” button.

Jenkins installation completed successfully.

Click on the “Start using Jenkins” button.

Everything is ready to use Jenkins.

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