DevOps Classroom Series (Evg) – 28/Nov/2021

Giving Necessary permissions to Jenkins User

• jenkins user needs to be given necessary permissions.
• Since we use jenkins for automation if the command we execute asks for a password jenkins will halt execution
• Now lets try to give sudo permission to the jenkins user which will not ask for a password
  • Note: This is a linux configuration for a jenkins user on linux node
  • commands:

  # become a root user
  sudo -i
  visudo
  # make changes as shown below and save the file
  

  
  • Now lets look at the jenkins job config

Lets disect the Jenkins Free Style Project

• This is classic way of creating jenkins job.
• Jenkins freestyle project has the following sections
  • General:
    • This section is about describing the basic configurations of your project
  • Source Code Management:
    • In this section we try to configure the version control system from where the code needs to be picked up
  • Build Triggers
    • This section will help in configuring when should be job triggered/executed
  • Build Environment
  • Build: This is the core activity for doing ci/cd i.e. building or deploying the code
  • Post Build Actions: After the build is completed (success or failure) configuring next steps is done from here
• Screenshot
• Now lets create a jenkins job by configuring SCM and build step
• NOte: To explore install tree (sudo apt install tree -y)
• Now lets explore the /var/lib/jenkins
• lets explore the /var/lib/jenkins/jobs
• we have created a job called as exploring
• The configurations are stored as xml file under /var/lib/jenkins/jobs/<job-name>/config.xml
• Now lets build the exploring job
• Now lets explore the workspace folder
• In the workspace/<project-name> the files are created depending on the steps configured in jenkins job
• Workspace contains the code cloned and files created as the result of the commands executed during build process.
• jobs folder will create the files when we create a job and build is generated.
• When we create any stuff in jenkins it will be stored in /var/lib/jenkins which is referred as JENKINS_HOME directory.
• If you want to backup jenkins then take the backup of JENKINS_HOME directory
• Lets change the build to show environment variables. Run the jenkins job
  • Following are the list of ENVIRONMENT Variables shown in output

    BUILD_DISPLAY_NAME='#3'
    BUILD_ID='3'
    BUILD_NUMBER='3'
    BUILD_TAG='jenkins-exploring-3'
    BUILD_URL='http://35.86.87.190:8080/job/exploring/3/'
    CI='true'
    DBUS_SESSION_BUS_ADDRESS='unix:path=/run/user/113/bus'
    EXECUTOR_NUMBER='1'
    GIT_BRANCH='origin/master'
    GIT_COMMIT='71343d252fdc7b6c6f05c6ae88231445e0c72a5a'
    GIT_PREVIOUS_COMMIT='71343d252fdc7b6c6f05c6ae88231445e0c72a5a'
    GIT_PREVIOUS_SUCCESSFUL_COMMIT='71343d252fdc7b6c6f05c6ae88231445e0c72a5a'
    GIT_URL='https://github.com/GitPracticeRepo/understanding.git'
    HOME='/var/lib/jenkins'
    HUDSON_COOKIE='06bc3074-9d40-458a-b041-4a30789f1122'
    HUDSON_HOME='/var/lib/jenkins'
    HUDSON_SERVER_COOKIE='c175908bb1344434'
    HUDSON_URL='http://35.86.87.190:8080/'
    IFS=' 	
    '
    JENKINS_HOME='/var/lib/jenkins'
    JENKINS_SERVER_COOKIE='c175908bb1344434'
    JENKINS_URL='http://35.86.87.190:8080/'
    JOB_BASE_NAME='exploring'
    JOB_DISPLAY_URL='http://35.86.87.190:8080/job/exploring/display/redirect'
    JOB_NAME='exploring'
    JOB_URL='http://35.86.87.190:8080/job/exploring/'
    LANG='C.UTF-8'
    LOGNAME='jenkins'
    MAIL='/var/mail/jenkins'
    NODE_LABELS='master'
    NODE_NAME='master'
    OPTIND='1'
    PATH='/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin'
    PPID='5405'
    PS1='$ '
    PS2='> '
    PS4='+ '
    PWD='/var/lib/jenkins/workspace/exploring'
    RUN_ARTIFACTS_DISPLAY_URL='http://35.86.87.190:8080/job/exploring/3/display/redirect?page=artifacts'
    RUN_CHANGES_DISPLAY_URL='http://35.86.87.190:8080/job/exploring/3/display/redirect?page=changes'
    RUN_DISPLAY_URL='http://35.86.87.190:8080/job/exploring/3/display/redirect'
    RUN_TESTS_DISPLAY_URL='http://35.86.87.190:8080/job/exploring/3/display/redirect?page=tests'
    SHELL='/bin/bash'
    SHLVL='0'
    USER='jenkins'
    WORKSPACE='/var/lib/jenkins/workspace/exploring'
    WORKSPACE_TMP='/var/lib/jenkins/workspace/exploring@tmp'
    XDG_DATA_DIRS='/usr/local/share:/usr/share:/var/lib/snapd/desktop'
    XDG_RUNTIME_DIR='/run/user/113'
    XDG_SESSION_CLASS='background'
    XDG_SESSION_ID='c1'
    XDG_SESSION_TYPE='unspecified'
    _='/usr/bin/daemon'
    

  • Lets see the list of the environmental variables
  • We can use this environmental variables in the build command

Lets create our first build project for java

• Before we configure building on jenkins, lets try to understand how to build a java project manually
• Lets try to build the project Refer Here hosted on github
• To build this project
  • Softwares:
    • git
    • java 11 jdk
    • maven
• We have create a test server and installed the above mentioned softwares
• Executed the following commands

git clone https://github.com/graalvm/graal-js-jdk11-maven-demo
cd graal-js-jdk11-maven-demo
mvn package

• If we want to run this as a project on our jenkins server

  • we need to install maven

• Now create a jenkins job

• Now lets build the jenkins job

Maven

• For java applications to build the code the APACHE Ant tool was introduced where you create a configuration file build.xml where you specify the build steps once and run it multiple times using ant tool Refer Here for the sample
• Maven is build with an approach Convention over configuration
• When developers build projects they use external java libraries
  • Maven has an easy way to do dependency management.
  • Maven can help in creating the basic folder structures