Build a CI testing environment to automatically running the build, testing actions whenever the code in remote repository changes.

1. In terminal, to run docker-compose up -d, to setup Jenkins, private registry

2. Push any images depends on the project to the private registry running at localhost:5001, e.g.,

   docker push localhost:5001/my-ubuntu

3. Browse to http://localhost:8080, setting up the Jenkins project.

   When you first access a new Jenkins instance, you need to finish the initial setup, such as unlocking Jenkins,
   installation of plugins, creating the first administrator user, and add a new global credential for docker agent.
   Or you can run the command docker exec <jenkins-container-name> bash -c "/var/jenkins_home/post_installation.sh"
   to automatically setup jenkins and configure the docker agent of Jenkins.

   Add a new global credential for docker agent

   1. From the Jenkins home page, click Manage Jenkins > Manage Credentials.

   2. Under Stores scoped to Jenkins on the right, click on Jenkins.

   3. Under System, click the Global credentials (unrestricted) link to access this default domain.

   4. Click Add Credentials on the left.

   5. From the Kind field, choose the X.509 Client Certificate to add.

   6. From the Scope field, choose Global.

   7. Copy and paste the appropriate details into the Client Key, Client Certificate and Server CA Certificate fields.

      Client Key, obtain by running docker exec <dind-container-name> cat /certs/client/key.pem

      Client Certificate, obtain by running docker exec <dind-container-name> cat /certs/client/cert.pem

      Server CA Certificate, obtain by running docker exec <dind-container-name> cat /certs/server/ca.pem

   8. In the ID field, specify a meaningful credential ID value.

   9. Click OK to save the credential.

   10. After creating your credential, click Manage Jenkins > Manage nodes and clouds > Configure Clouds > Docker Cloud details.
       From the Server credentials, choose the id of the credential you created previously and click the Test Connection button and
       you should see the information of the docker daemon.

In Jenkins, we can use webhooks to have GitHub notify Jenkins whenever the code in GitHub changes.
Jenkins can respond by automatically running the build to implement any changes.

Configuring webhooks in Jenkins. We neet to:

• Create an access token in GitHub that has permission to read and create webhooks

• Add a GitHub server in Jenkins for GitHub.com

• Create a Jenkins credential with the token and configure the GitHub server configuration to use it

• Check "Manage Hooks" for the GitHub server configuration

• In the project configuration, under "Build Triggers" select "GitHub hook trigger for GITScm polling"