DevOps Classroom Series – 25/Sept/2020

What is cronjob or Scheduled Job?

• Cronjobs are jobs (scripts, executables) that you want to run on a particular schedule (Specific time, periodic) on Linux based systems. (Schedule Jobs are for Windows)
• Cronjob uses the following format

MIN HOUR DOM MON DOW CMD

• Now Lets execute a script called as fullbackup.sh in the directory /opt/backups/fullbackup.sh

30 08 10 * * /opt/backups/fullbackup.sh

Jenkins

• Jenkins is cron/scheduler on Steriods to run CI/CD activities
• How to install Jenkins Master on Linux Machines?

Installation in Ubuntu

• Refer Here for ubuntu steps documentation

sudo apt update
sudo apt install openjdk-8-jdk -y
java -version
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 navigate to http://<ipaddress&gt;:8080

• To install specific version of jenkins refer here

• What happened during installation

  • Jenkins creates a user and a group called as jenkins
  • This means when we run any job from jenkins ui the job will be executed on the linux machine as jenkins user
  • Lets login as jenkins user and verify certain items
  • Jenkins stores all of its data in the directory referred as JENKINS HOME DIRECTORY. In our case is /var/lib/jenkins
  • Now lets create a simple jenkins job/project
  • Now navigate into jenkins home directory and explore jobs folder. You will findout jenkins job which we created on ui is stored as an xml file <projectname>/config.xml
  • Lets change our job to create a file as part of build

Summary

• When we install jenkins a user called as jenkins and a group called Jenkins will be created.
• When we create jobs, jobs are stored as xml files in jenkins home directory/jobs folder
• When we execute jobs, Jenkins uses workspace folder.