How to Update Jenkins in Docker: The Correct Approach

Jenkins is a widely used Continuous Integration and Continuous Deployment (CI/CD) tool. While it can be deployed in Docker containers for easy management and scalability, it’s important to know the right steps to update Jenkins in Docker. Incorrectly updating Jenkins can lead to downtime and potential service interruptions. In this article, I will guide you through the proper way to update Jenkins in Docker.

Understanding the Process

Many may think that to update Jenkins in Docker, one would simply need to stop the current container and replace it with a new one. However, this is not the case. Rather than stopping and removing the existing Jenkins container, we should create a new container with the updated version of Jenkins and use it instead. Here’s a step-by-step guide to updating Jenkins in Docker effectively.

Step-by-Step Guide to Updating Jenkins in Docker

1. Stop the Current Jenkins Container

The first step is to stop the running Jenkins container. Use the following command to stop the container:

docker stop jenkins

This command will stop the Jenkins container, but it will not delete its contents. The Jenkins data is saved, and you can safely proceed to the next step.

2. Clean Up the Old Jenkins Container

Next, delete the old Jenkins container to free up the name and potentially clean up any residual resources. Use the following command to remove the container:

docker rm jenkins

Make sure the container is stopped before removing it to avoid any conflicts.

3. Update Jenkins to the Latest Version

Now, pull the latest version of Jenkins from the Docker Hub. Execute the following command:

docker pull jenkins

This command will download the latest Jenkins image from the Docker Hub, which you can use to start a new container with the updated Jenkins version.

4. Start the New Jenkins Container

Create a new container with the updated Jenkins image by executing the following command:

docker run -d -p 8080:8080 --privileged -v /path/to/your/jenkins/data:/var/jenkins_home --name jenkins jenkins

Let’s break down this command: -d runs the container in detached mode, allowing you to work in the terminal without the container being attached. -p 8080:8080 maps port 8080 on the host machine to the same port in the container, making it accessible. --privileged gives the container extra permissions, which may be necessary for certain operations. Be cautious when using this flag. -v /path/to/your/jenkins/data:/var/jenkins_home mounts a volume for persistent storage, so your Jenkins data persists across container reboots. --name jenkins names the container for easy reference. jenkins is the image name pulled in the previous step.

Why Not Simply Remove and Replace?

Some might think that stopping, removing the container, and then recreating it from a fresh image is the way to go. However, this approach has some drawbacks. First, it requires you to manually copy all the Jenkins data from the old container to the new one. This can be time-consuming and error-prone. Second, it risks losing any mounted volumes and mounts, which are essential for persistence and stability.

By following the steps outlined above, you ensure that your Jenkins setup remains stable, and your data is safely preserved.

Further Considerations

Updating Jenkins in Docker should not be a frequent operation, but when it is necessary, consider the following tips:

Ensure you have the necessary permissions to perform these Docker commands and to restart or modify Jenkins. Backup your Jenkins data before performing any updates to prevent data loss. Test the updated Jenkins in a staging environment before rolling it out to production to ensure everything works as expected. Maintain your Docker images and Jenkins plugins to stay up-to-date with the latest security patches and features.

In conclusion, updating Jenkins in Docker requires a careful and strategic approach. By following the steps outlined in this article, you can confidently manage your Jenkins CI/CD pipeline without downtime or data loss.