Page of tips and how-tos for Jenkins.

At Jenkins:

• Install plugin "GitHub"

At GitHub, create account personal token:

• Under profile, navigate menus Settings -> Developer Settings -> Personal Access Tokens
  • Generate new token
    • Note = Jenkins (any name desired)
    • Select scopes (at least scopes <admin:repo_hook> and <repo:status>)
    • Click generate token and COPY IT!

At Jenkins, create GitHub credentials:

• Under profile, navigate menu Credentials
  • In "Stores from parent", click "Jenkins"
    • In "System", click "Global credentials"
      • Add credentials
        • Kind = Secret text
        • Scope = Global
        • Secret = CTRL-V token generated at GitHub
        • ID = GithubTokenCredential (any name desired)
        • Description = Personal access token from GitHub (any description desired)
        • Click OK

At Jenkins, add GitHub server:

• Navigate menus Manage Jenkins -> Configure system
  • In the section "Github"
    • Add Github Server
    • Name = MariMendMGitHub (any name desired)
    • API URL = https://api.github.com
    • Credentials = GithubTokenCredential (the one created above; will be identified by Description instead of ID)
    • Click "test connection"; it shall work!
    • Enable option "manage hooks"
    • Click "advanced options" (the one from section GitHub, not the one from GitHub Server itself)
      • Enable option "override hook URL" and copy URL displayed (something like http://<DNS-or-IP>:8080/github-webhook/)
    • Click "save"

Create SSH private/public pair of keys:

• At linux, use "ssh-keygen"
  • Private key will be used in JENKINS
  • Public key will be used in GitHub

At GitHub, configure SSH credential:

• Under profile, navigate menus Settings -> SSH and GPG Keys
  • Click "New SSH key"
    • Title = Jenkins (any name desired)
    • Key = CTRL-V <public> key generated
    • Click "Add SSH key"

At Jenkins, create GitHub credentials:

• Under profile, navigate menu Credentials
  • In "Stores from parent", click "Jenkins"
    • In "System", click "Global credentials"
      • Add credentials
        • Kind = SSH Username with private key
        • Scope = Global
        • ID = GithubSSHCredential (any name desired; it is the name used inside jenkinsfile)
        • Description = SSH private key to GitHub for groovy script (any description desired)
        • Username = GitHub account user name
        • Private key = CTRL-V <private> key generated
        • Passphrase = leave blank (or fulfill it with passphrase from key file, as input in ssh-keygen)

Example of pipeline's groovy script stage using SSH credentials:

  stage('Cloning github repository')
  {  steps
     {   git url: '[email protected]:MariMendM/examplerepo.git', credentialsId: 'GithubSSHCredential'
     }
  }

Considerations before start:

• Next steps assume a pipeline is already created
• Jenkins' job must be run at least once manually before the hook will work

At Jenkins, configure Jenkins' part of webhook:

• Navigate to pipeline job, menu Configure
  • In section "general", enable option "GitHub project"
    • Input project URL (something like https://github.com/MariMendM/devops_sandbox/)
  • In section "build triggers", enable option "GitHub hook trigger for GITScm polling"
  • Click Save

At GitHub, configure GitHub's part of webhook::

• Navigate to repository, menus Settings -> Webhooks
  • Add Webhook
  • Payload URL = CTRL-V hook URL from Jenkins Server Configuration (something like http://<DNS-or-IP>:8080/github-webhook/ - it must end with "/")
  • Content type = application/json (or application/x-www-form-urlencoded for Pull Request events in Freestyle Jobs)
  • Secret = leave blank (TO-DO: test with secret)
  • Select events to trigger the webhook
  • Click "add webhook"

At Jenkins:

• Install plugin "Docker Pipeline"

At Jenkins's host:

• Install Docker
• Add Jenkins user to docker group

   sudo usermod -a -G docker jenkins

• Restart Jenkins

   sudo service jenkins restart

At DockerHub, create account access token:

• Under profile, navigate menus Account Settings -> Security
  • Click "New access token"
    • Access Token Description = Jenkins (any name desired)
    • Click "Create" and COPY IT!

At Jenkins, create DockerHub credentials:

• Under profile, navigate menu Credentials
  • In "Stores from parent", click "Jenkins"
    • In "System", click "Global credentials"
      • Add credentials
      • Kind = Username with password
      • Scope = Global
      • Username = DockerHub user name
      • Password = CTRL-V token generated at DockerHub
      • ID = DockerhubUsrTokenCredential (any name desired; it is the name used inside jenkinsfile)
      • Description = User and access token from DockerHub (any description desired)
      • Click OK

At Jenkins, Configure Docker:

• Navigate menus Manage Jenkins -> Configure system
  • In the section 'Declarative Pipeline (Docker)'
    • Docker Label = leave empty (used when docker is not installed on the same Jeninks' host)
    • Docker Registry URL = https://hub.docker.com/
    • Registry Credentials = DockerhubUsrTokenCredential (created above)

Considerations before to start:

• SMTP Port shall be opened for outbound in Jenkins server

At Jenkins:

• Install plugin "Email Extension Plugin"

At Gmail's Google Account (with 2FA activated):

• Navigate Manage google account -> Security
  • In "Signing in to Google", click "App Passwords"
    • Select app = email
    • Select device = Other (type something like Jenkins)
    • Click "Generate" and COPY IT!

At Jenkins, configure SMTP:

• Navigate menus Manage Jenkins -> Configure system
  • In section "Extended Email Notification"
    • SMTP Server = smtp.gmail.com
    • SMTP Port = 465
    • Click advanced
      • Username = gmail's email to be used as sender ([email protected])
      • Password = type password or token provided at gmail's step above
      • Enable "Use SSL"
    • Default user email suffix : @gmail.com
    • Configure predefined fields, if desired
    • Click "Default triggers" and choose automatic emails (if desired)

At Jenkins pipeline's groovy script:

• Example01: via emailext step

	emailext body: 'Test Message',
		subject: 'Test Subject',
		to: '[email protected]'

• Example02: via emailext step, using plugin's global configuration (available tokens are documented at Manage Jenkins -> Extended Email Notification)

	emailext body: '$DEFAULT_CONTENT',
		subject: '$DEFAULT_SUBJECT',
		to: '[email protected]'		

• Example03: to add all people who caused a change in the change set and the user who initiated the build:

	emailext body: "Build ${env.BUILD_TAG} successful",
		recipientProviders: [developers(), requestor()],
		subject: 'Test Subject',
		to: '[email protected]'