Jenkins Installation on CentOS7/RHEL/Fedora and Ubuntu

Hello DevOps enthusiast, I'm here with another interesting article on one more DevOps automation tool that is Jenkins CI, where I've explored all possible new learnings which will be used by DevOps.

Jenkins installation on CentOS or RHEL or Fedora

Simple instructions I've made for reference, which I've used.

What are the Pre-requisites for the Jenkins installation

• Good speed of Internet
• Either of the platforms will be working:
• Vagrant installed VirtualBox installed to pull CentOS7 box
• AWS RHEL instance up and running 

Bring up the CentOS/7 box (optional)

Note: Ignore this section if you have a Cloud instance ready.

Step 1: Create your own CentOS7 vagrant box with the following DSL Vagrantfile:

Vagrant.configure(2) do |config|
  config.vm.box = "centos/7"
  config.vm.boot_timeout=600
  config.vm.host_name = "mydev.devopshunter.com"
  config.vm.network "private_network", ip: "192.168.33.100"
  config.vm.synced_folder "C:/Softwares", "/u01/app/software"
  config.vm.provider "virtualbox" do |vb|
    vb.cpus = "2"
    vb.memory = "2048"
  end
end

Now based on the above Vagrantfile, bring up the vagrant CentOS box:

vagrant up

Now all set to go, Connect to the vagrant box using PuTTY, SSH-> Auth -> centos.ppk file. Create an aws instance and connect it with the putty or git bash client.

Step 2: Switch to root user, download the Jenkins installer using wget, you can find the stable and latest version of Jenkins RPM File here you can see the latest at the bottom of the page. and the installation with rpm command as:

sudo -s
#install wget if not installed on cloud instances
yum install wget epel-release daemonize -y

# Latest version of Jenkins requires daemonize package dependency
wget https://pkg.jenkins.io/redhat/jenkins-2.192-1.1.noarch.rpm
rpm -ivh jenkins-2*.rpm

Jenkins installation using rpm option

Jenkins installation on Ubuntu

Note: This section added in the year July 2022.
Recent changes in the Ubuntu publick key authentication on the debain package manager.

sudo apt update
sudo apt install default-jre
curl -fsSL https://pkg.jenkins.io/debian/jenkins.io.key | sudo tee   /usr/share/keyrings/jenkins-keyring.asc > /dev/null
echo deb [signed-by=/usr/share/keyrings/jenkins-keyring.asc]   https://pkg.jenkins.io/debian binary/ | sudo tee   /etc/apt/sources.list.d/jenkins.list > /dev/null
sudo apt-get update
sudo apt-get install jenkins
systemctl status jenkins

How to install Open JDK on CentOS?

Once the Jenkins installation completed we need to run with JRE, We have two choices - Open JRE, or Oracle JRE to run Jenkins CI. JRE is part of JDK so let's install Open JDK. Using `yum` repo we can install the OpenJDK which also includes Open JRE.

yum install -y java 
#Check Java installation successful
java -version

Now we are done with the installation part move to bring up the Jenkins CI service.

Starting your Jenkins CI master on CentOS7

Every RHEL flavor Linux versions support service command to run the service in the background and will be executed when a software added to the system, systemctl will help us to control it for start or stop or restart and to check the status of the service.

service jenkins start
chkconfig jenkins on

Let's check the status of the Jenkins service:

service jenkins status -l

Check the Jenkins service status

How to accessing your Jenkins CI URL?

By default Jenkins runs on the 8080 port combination with the IP address as shown:

http://<jenkins ip> :8080/

On my Vagrant box I can access the Jenkins URL as an example:
http://192.168.33.100:8080/

Jenkins first-time UI

Wow!! Lovely, We are ready to operate on Jenkins now you can set the value present Password in the given path and copy it and reset the user profile and password values which will be overrides the default/one time password.

How to create First Admin user on Jenkins?

Here is the sample user profile setting details:

• User name: ci_admin
• Password : welcome1 [you can provide much stronger one for your CI project]
• Confirm Password : welcome1
• Full name : Continuous Integration admin
• Email:  ignore [optional]

Create First Admin User sample

Click on the '   Save and Continue  ' button then it navigates to 'Instance Configuration' page, shows Jenkins URL.

How to configure Remote Agent using WebSocket?

1. Please enter the "Name" that uniquely identifies an agent in the Jenkins domain.

2. Enter Remote root directory such as /workspace

3. Enter the "Label" value this is the hook to run remotely any build.

4. Under Launching method 

Launch agent by connecting it to the controller

choose -> Use WebSocket tic the checkbox.

Jenkins Slave WebSocket Configuration

Save the configuration by hitting "save" button.

Slave configuration you can use the following shell script:

#!/bin/bash

# Ensure JDK installed on the agent box
AGENT_CMD='java -jar agent.jar -jnlpUrl http://mstr:8080/computer/node1/jenkins-agent.jnlp -secret 5650304d6aae3ebf424479e20978a7cd1408e3f539e243cbd309abbccd88a3 -workDir "/tmp/jenkins"'
nohup $AGENT_CMD > node1-vt-agent.out 2>&1 &

# print the log output
tailf node1-vt-agent.out
  

Executed on node1 example screenshot

Enjoy the Continuous integration fun with Jenkins!!