![]() That way the layers that are created first will be cached and reused. To fully take advantage of layer caching, write your Dockerfiles in a way that commands that will not change often are executed before others. You can refer to the official docs for further details. `docker build -target release -tag image. In this multi-stage Dockerfile we created a base image that has all the required dependencies, we then created a builder stage, and finally, for the actual runtime image, we started from a clean image, installed the production requirements, and selectively copied only the required artifacts.īy default, all stages are built but we can choose to build a specific stage with the flag `-target ` ![]() # Copy package.json and package-lock.json Let’s see a quick example: # Base image with dependencies In each FROM we can start from a previous stage in order to take advantage of cached build artifacts or we can start from an entirely new base image and just copy some artifacts from the previous stage. A multistage build consists of a single Dockerfile in which we define multiple FROM instructions and each one defines a new stage. Use multi-stage DockerfilesĪside from using Alpine as a base image, another method for reducing the size of your images is using multistage builds. For example, since Alpine is based on the musl C library, instead of the most widely used GNU C Library, you may encounter problems with some C-based dependencies. Keep in mind that it also has some drawbacks. It contains only absolutely necessary packages because you know… if it’s not included it can’t break. You can use `alpine:3.15` which is just about 5.6 MB instead of `ubuntu:20.04` which is (at the time of this article) 72 MB.Īlpine is a general-purpose Linux distribution built around musl libc and BusyBox that aims for simplicity, security, and resource efficiency. To achieve that, a good idea is to start from a base image that is itself very small. Keeping the size small generally means that it is faster to build, deploy and run. How can I keep my Docker image small? Start from a small base image. ![]() ![]() The Docker engine executes the commands sequentially and eventually combines all the layers to create the final image. ![]() Every time we execute a command in the Dockerfile, a new layer containing the changes is created on top of the previous one. When we start the build process from a Dockerfile, the Docker engine creates a series of layers, one for each command in the Dockerfile. It defines the base image from which we start, the application’s dependencies, how the application is packaged and how it is run. The Dockerfile is the main file that defines how a Docker image is built. In the next paragraphs, we will see a few tips on how we can avoid the most common security vulnerabilities and how to optimize the size of our Docker images.īut first, we need to understand one of the core concepts of Docker: the layering system. We already covered Docker in our blog, you can dig further on the origins of Docker or see a use case with Wordpress. Nowadays we have a lot of workloads that are built on top of Docker and it is crucial to keep our Docker images secure and optimized for the cloud. ![]()
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