Why use Jenkins or any other CI/CD Engine

• Refer the image below
• There are many alternatives to jenkins
  • Azure DevOps (VSTS)
  • Bamboo
  • TeamCity
  • Circle CI
• From Jenkins we need to create a pipeline to
  • get the latest version of the code
  • build the code into some package
  • run some code quality tools
  • upload the package to some repository
  • deploy the application into various test environments

Lets understand how jenkins works and important terms of jenkins

• Lets start the Jenkins server
• Jenkins Job: This is sequence of actions to be performed to realize a ci/cd pipeline or part of pipeline
  • To create a Jenkins job, in jenkins we need to create a jenkins project which specifies the steps to be performed as part of jenkins build.
• So when we execute a jenkins job/project then jenkins runs the steps mentioned in the job as a system user (default is jenkins) and shows the results
• Jenkins will store all of its configurations in JENKINS HOME Directory, In this case the jenkins home directory is /var/lib/jenkins
• The jenkins project which we create will be stored as an xml file in JENKINS_HOME/jobs/<jobname>/config.xml
• When we run the jenkins job, jenkins uses workspace folder to store the build generated files
• Lets change the hellojenkins job to create some file and build the jenkins job
• Lets create a jenkins job which will clone git repository Refer Here
• So if we know manual steps for building the application, creating test environment and executing tests can we do that in jenkins
• So jenkins can be looked as scheduler which can run commands provided by user
• Jenkins has other features to make this simple. To make them simple Jenkins uses Plugins. A Plugin is a feature extension for jenkins which provides the user interface (in many cases) and some functionality
• Now lets create a jenkins job to clone a game of life repository using these plugins
• Now lets try to create a jenkins job to update ubuntu packages

sudo apt update

• This fails as jenkins user does not have permissions to execute sudo commands
• Now lets add jenkins user to sudoers group and then execute the same job
• Now, Can we run python –version in jenkins job. But the result whether this will be success or not depends on
  • Whether python is installed or not on the Jenkins Machine
  • Whether the user jenkins has permission to execute python or not.
• Next Steps:
  • Lets learn how to build java code using maven