Jenkins is an open-source automation tool written in Java with plugins built for Continuous Integration purposes. Jenkins is used to build and test your software projects continuously making it easier for developers to integrate changes to the project, and making it easier for users to obtain a fresh build.

Why is Jenkins in Docker?

The main reason is that Jenkins pipelines work really well with Docker. Without Docker you need to install additional tools and add different agents to Jenkins. With Docker, there is no need to install additional tools, you just use images of these tools.

Does Jenkins have Docker?

The Jenkins project provides Docker images for controllers, inbound agents, outbound agents, and more. Beginning with Jenkins 2.307 released August 17, 2021 and Jenkins 2.303. 1 released August 25, 2021, the Docker images provided by the Jenkins project will use Java 11 instead of Java 8.