Docker vs Jib: What are the differences?

Introduction

This article will compare Docker and Jib, two popular tools used in the world of software development. Both Docker and Jib are used to build container images, which are self-contained and executable software packages that include all the necessary dependencies to run an application. However, there are several key differences between Docker and Jib that set them apart from each other.

1. Build Process: One of the key differences between Docker and Jib lies in their build processes. Docker builds container images by creating a Dockerfile, which is a text document that contains a set of instructions for building an image. These instructions can include commands to install dependencies, copy files, and configure the environment. On the other hand, Jib builds container images directly from the application's source code. It does not require a Dockerfile or any other external build configuration. This makes the build process with Jib simpler and more streamlined.

2. Image Layering: Another important difference between Docker and Jib is their approach to image layering. Docker builds container images using a layered approach, where each instruction in the Dockerfile creates a new layer. These layers are stacked on top of each other to form the final image. This allows for incremental builds and efficient use of storage space. Jib, on the other hand, uses a different approach called layerless image building. With Jib, the container image is built as a single, monolithic layer. This eliminates the need for layer management and reduces the complexity of the image.

3. Container Runtime: Docker and Jib also differ in terms of the container runtime they use. Docker relies on Docker Engine, a container runtime that can run containers on various platforms such as Linux, Windows, and macOS. Docker Engine provides a full-fledged container runtime environment with features like container isolation, resource management, and networking. Jib, on the other hand, is specifically designed for containerizing Java applications. It leverages the container runtime provided by the platform on which the Java application is run, such as Kubernetes or Google Cloud Run. This makes Jib more lightweight and focused on the Java ecosystem.

4. Configuration: Docker and Jib differ in their configuration options for building container images. Docker provides a wide range of configuration options through the Dockerfile, allowing fine-grained control over the build process. These options include specifying the base image, installing dependencies, setting environment variables, and exposing ports. Jib, on the other hand, follows a more opinionated approach. It abstracts away many of the configuration details, making it easier to build container images. Jib automatically determines the base image and sets up the runtime environment based on the application's dependencies and requirements.

5. Build Lifecycle: The build lifecycle in Docker and Jib also differs in terms of how it is triggered and executed. Docker builds are typically triggered manually or through a continuous integration (CI) pipeline. The Dockerfile is processed by the Docker daemon, and the container image is built and pushed to a container registry. Jib, on the other hand, integrates directly with the build tool used for the application, such as Gradle or Maven. The container image is built and pushed to a container registry as part of the application's build lifecycle. This makes the build process with Jib more streamlined and tightly integrated with the development workflow.

6. Integration with Container Registry: The final key difference between Docker and Jib lies in their integration with container registries. Docker provides a built-in container registry called Docker Hub, where container images can be stored and shared. Docker also supports integration with other container registries, such as AWS Elastic Container Registry and Google Container Registry. Jib, on the other hand, integrates directly with container registries provided by cloud platforms. For example, Jib can push container images to Google Container Registry or Docker Hub without the need for additional configuration or authentication.

In summary, Docker and Jib are both powerful tools for building container images, but they have distinct differences in terms of their build processes, image layering, container runtime, configuration options, build lifecycle, and integration with container registries. The choice between Docker and Jib depends on the specific requirements of the project and the development workflow.