Jenkins – getting started

Stand alone installation

is the easiest option to explore & get familiar with Jenkins. This is not a recommended production setup, as stopping (ctrl+c) the Linux command (java -jar jenkins.war) would terminate the Jenkins session.

All that is needed is Jenkins war (web archive) file, which can be download from the official website –> https://www.jenkins.io/download/

mkdir jenkins
cd jenkins
wget https://mirror.gruenehoelle.nl/jenkins/war-stable/2.235.5/jenkins.war
java -jar jenkins.war

The installation would reveal an initial password to proceed

Browse to http://localhost:8080 and wait until the Unlock Jenkins page appears.

Use the initial password to unlock and ‘Install suggested plugins’ to customize Jenkins.

Fill the details in the following screen to land on the Jenkins home page and start exploring Jenkins

Deploy on Application Server

Install any application server & then deploy Jenkins application on top. This method is one of the preferred approach for a production installation as application servers are routinely managed as part of the landscape.

I’m using Apache Tomcat 9 as my application server & installing it by using these easy commands

sudo apt-get update
sudo apt-get install -y tomcat9
sudo service tomcat9 status

Once the tomcat server is up and running, place the jenkins.war file in the /var/lib/tomcat9/webapps folder & restart the tomcat service

sudo cp ~/jenkins/jenkins.war /var/lib/tomcat9/webapps/
sudo service tomcat9 restart

All seems OK and Jenkins should be accessible by browsing  http://localhost:8080/jenkins, but instead you experience an error

This error happens because the Jenkins application is being executed by the tomcat user (created by the app server installation), while it’s expecting a jenkins user. There are 2 ways to resolve the issues

sudo apt-get -y remove tomcat9
sudo rm -rf /var/lib/tomcat9

I am following approach 1 wherein a user ‘tomcat’ is created, added to the sudoers group, tomcat is re-installed & jenkins.war file copied to the webapps folder

sudo useradd tomcat
sudo usermod -aG sudo tomcat
su - tomcat
sudo apt-get -y install tomcat9
sudo cp /home/arvind/jenkins/jenkins.war /var/lib/tomcat9/webapps/

Now browsing to http://localhost:8080/jenkins would show the ‘Unlock Jenkins’ screen

Install Jenkins as service

Jenkins can also be installed using the package managers, like apt in case of Ubuntu

A LTS (Long-Term Support) release can be installed from the debian-stable apt repository.

wget -q -O - https://pkg.jenkins.io/debian-stable/jenkins.io.key | sudo apt-key add -
sudo sh -c 'echo deb https://pkg.jenkins.io/debian-stable binary/ > \
    /etc/apt/sources.list.d/jenkins.list'
sudo apt-get update
sudo apt-get install jenkins

This package installation will:

• Setup Jenkins as a daemon launched on start. See /etc/init.d/jenkins for more details.
• Create a ‘jenkins’ user to run this service.
• Direct console log output to the file /var/log/jenkins/jenkins.log. Check this file if you are troubleshooting Jenkins.
• Populate /etc/default/jenkins with configuration parameters for the launch, e.g JENKINS_HOME
• Set Jenkins to listen on port 8080. Access this port with your browser to start configuration.
  • If your /etc/init.d/jenkins file fails to start Jenkins, edit the /etc/default/jenkins to replace the line ----HTTP_PORT=8080---- with ----HTTP_PORT=8081---- Here, “8081” was chosen but you can put another port available.

All Done. Browse to http://localhost:8080 and wait until the Unlock Jenkins page appears.

Jenkins as Docker Container

Well if you wanna beat the queue and straight jump into the world of ‘Containers’, then install the latest version of Docker Daemon using these commands

sudo apt-get -y update && sudo apt-get -y upgrade
sudo apt-get insatll -y curl
sudo curl -fsSL https://get.docker.com -o get-docker.sh
sudo sh get-docker.sh

Any non-root user can access the Docker service once added into the Docker group & then start the docker service

sudo usermod -aG docker <username>
sudo service docker start
sudo service docker status

With the Docker Daemon up and running, Jenkins container can be launched using the following comand