Let's configure a Jenkins job to build a sample microservice application, which was introduced in the previous recipe (my-calc). Perform the following steps to configure and build a Docker image:

1. On the left navigation, click New Item:

2. Put your in desired item name (example: my-calc), select Freestyle project, then click OK:

3. In the Source Code Management tab, select Git and set the Repository URL as https://github.com/kubernetes-cookbook/my-calc.git, or you may use your own repository which has a Dockerfile:

4. On the Build Environment tab, click Add build step to add Build / Publish Docker Image:

5. In the Build / Publish Docker Image panel:
   1. Directory for Dockerfile as current (.)
   2. Choose my-docker in the Cloud that we've set up
   3. Put image as your Docker repository, but append :${BUILD_NUMBER} (example: hidetosaito/my-calc:${BUILD_NUMBER})
   4. Enable Push image
   5. Click Add to add your Docker hub ID credential
   6. Then, click Save:

6. Finally, you can click Build Now to trigger a build; for testing purposes you can click five times to see how it works:

7. Note that you can see a Console that knows it performs a Docker build and push:

8. Access your Docker hub repository; it has been pushed five times (because of clicking on build five times):

That's it! You can achieve continuous integration to build a Docker image so that when you update a source in GitHub, you can continuously build and push the latest image to your Docker hub repository by Jenkins.