Configuring Fresh Jobs in Jenkins

Hello, Dear DevOps Automation enthusiast! This post is intended targeted to those who have just started the journey in the Continuous Integration and Continuous Deployment on the Cloud Platforms or On-premises environments.

Pre-requisites

• Latest Stable version of Jenkins installed 
• Jenkins Master is in running state on your machine/VM/Cloud instance
• Able to login to the Jenkins Console

In the left pane, you can click on 'New Item' or Click on the 'Start Using Jenkins' link. The welcome screen shows a link to create a new job!

Jenkins First Job Project creation

You need to enter the value for 

Name for the build project

Type of project

1. Freestyle Project
2. Pipeline
3. Multi-configuration Project
4. Folder
5. GitHub Organization
6. Multibranch Pipeline

Enter the name of the project, Select the 'Freestyle project' for the first time and click on the 'OK' button. New page loads with 6 sections/tabs for build project inputs.

Job Configuration Sections

In Jenkins console we have various Job Configuration types

1. General - Description of the project, Enable project based security, change date pattern for BUILD_TIMESTAMP, Discard old builds enable will help you for easy migration of Jenkins master.
2. Job Notification -  End points, You can enable notification mail when someone changed configuration. Rebuild without asking parameters or we can disable the rebuild for a particular job. You can choose the build requires lockable resources, which means other jobs not allowed when this job is in progress. This project is parameterized enabled then you can add different type Parameters such as String Parameter, Choice Parameter, Password Parameter, Node
4. Jenkins job configuration allows us to use 5 different choices of 'Source code management' as:

a. None

b. CVS

c. CVS Projectset

d. Git

e. Subversion

        Default it is selected as - None

Build Trigger

1. Jenkin's job will be triggered by a 'Build Triggers' section. Here we have Trigger build remotely from scripts, 
2. Build after other projects are built when there is dependency are in the projects
3. Build periodically - This choice asks you on what period you want to execute this job
4. Enable Artifactory trigger - when docker image is pushed you want to run a job 
5. GitHub hook trigger for GITscm polling - requires authentication for webhook accessing GitHub repository
6. Poll SCM - for all types of source code repository updates can trigger the job.

Build Environment

Usually, when we run a build, Jenkins uses /tmp/somerandomnumber.sh in Linux machines as the automatically generated script will create workspace in the slave machine. 

1. Delete workspace before build starts
2. Use secret text(s) or file(s)
3. Provide configuration files
4. send files or execute commands over SSH before the build starts 
5. send files or execute commands over SSH after the build runs
7. Abort the build if it's stuck
8. Add timestamps to the Console Output
9. Ant/Ivy-Artifactory Integration
10. Create a formatted version number
11. Farm Repository
12. Generic-Artifactory Integration
13. Gradle-Artifactory Integration
14. Inject environment variables to the build process
15. Inject passwords to the build as environment variables
16. Inspect build log for published Gradle build scans
17. Maven3-Artifactory Integration
18. Run Xvnc during build
19. Setup Kubernetes CLI (kubectl)
20. With Ant

Build

The build section will have an Execute shell with command text box. where you can enter the shell commands. which will become a shell script.

2. Pipeline Project

If you choose the Pipeline Project then it will have the following sections

1. General

2. Job Notifications

3. Build Triggers

4. Advanced Project options

5. Pipeline 

General 

In the General section, you can see

Enable project-based security

Discard old builds when you check this -> Strategy where you have LogRotation based on - Days to keep builds or Max # of builds to keep 

Advance option - 

Days to keep artifacts - if not empty default 14, artifacts from builds older than this number of days will be deleted, but the logs, history, reports, etc for the build will be kept

Max # of builds to keep with artifacts - if not empty, only up to this number of builds have their artifacts retained

Do not allow concurrent builds

Do not allow the pipeline to resume if the master restarts

GitHub project

Job Notifications

Notify when Job configuration changes

Pipeline speed/durability override

Preserve stashes from completed builds

  Rebuild options: Rebuild Without Asking For Parameters

  Disable Rebuilding for this job

Sidebar Links

This project is parameterized selected then you are allowed to use following parameters:

1. Node
2. String
3. Active Choices parameter -> 
1. Name 
2. Script option will have choice to enter the Groovy script
3. Choice type:  Single select, Multi select, Radio button, Checkbox 
4. Enable Filters
5. The filter starts at 1

Build Triggers

1. Build after other projects are built
2. Build periodically
3. Build whenever a SNAPSHOT dependency is built
4. Enable Artifactory trigger
5. GitHub hook trigger for GITScm polling
6. Poll SCM
7. Disable this project
8. Quiet period
9. Trigger builds remotely (e.g., from scripts)

Advanced Project Options

Click on the 'Advanced' button

Pipeline

Definition - Pipeline script

    the script, Use Groovy sandbox.

After you configured the Job, you have to Apply to save the configuration until now. 

If you are working on the Visual Studio code as editor then you can install the Extention. 

Groovy extension

Jenkinsfile Extension

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!!