DevOps Classroom Series – 10/Jul/2021

Exploring Jenkins

• So lets get started by installing jenkins. Refer Here
• Today we will be using a linux machine to install jenkins which has ubuntu distribution
• This setup will be done on AWS with 2 vCPUs and 8 GB of RAM
• Jenkins History
• Installing Jenkins on Ubuntu 18.04:
  • Login into the jenkins using ssh
  • Lets see the list of users on the linux machine
  • To install jenkins we need to java installed for java requirements Refer Here
  • Lets try to install java 11
  • Install by executing the command sudo apt install openjdk-11-jdk -y
  • Install jenkins by executing the below commands

  sudo apt update
  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
  

  
  • Now lets see the list of the users
  • A New user called as jenkins is created and the home directory of this user is /var/lib/jenkins
  • Jenkins runs on port 8080 so navigate to http://<public-ip>:8080
  • Follow the installation steps as discussed in the classroom.

Basic Jenkins Terminology

• Project/Job: This is where we define the steps to be executed.

Exploring & understanding

• Steps
• When i run/build a project in jenkins it is running as a newly created jenkins user
• So jenkins is nothing but a scheduler which runs the linux commands as some linux user.
• To make the life simple, jenkins creates some ui components which are friendly towards building a project (CI/CD)

Manual Scenario 1

• Cloning the project from git. For this lets take a project called as spring pet clinic Refer Here

• To clone a project from git we require

  • git to be installed
  • probably internet connection
  • some disk space

• Create a Jenkins job and in the build step type git clone command.

What is Jenkins Plugin

• Lets try to clone the spring pet clinic repository as mentioned above
• Lets look at git plugin
• plugin is a UI developed which will translate into low level commands. These UI will help in doing the job easily.

Lets try to build java 11 project

• clone the git repository Refer Here and cd into java-11-projects then execute

mvn package

• To make this command work install maven

sudo apt install maven -y

• If we can execute the command manually on the linux machine it will work from jenkins as well.

Lets try to execute sudo commands from jenkins

• The commands to be executed are

sudo apt update

• Lets create the jenkins job
• The Status is
• Just because commands work on the system doesnot mean they will work from jenkins. To evaluate whether they work or not we need to work with jenkins user
• Now added jenkins user to sudoers file with NOPASSWD option