Here is where Alpine Linux based images come in handy, as they contain only the most essential Linux packages. In a production environment you need code to be deployed quickly. Alpine Linux ImageĪlpine Linux Images are minimalist Docker images that are only 5 MB in size. I would highly recommend reading the Dockerfile of the image you choose, it may be hard to understand when you first get started but it’s an essential skill to acquire. If for some reason you are unable to find a relevant Official image, you could consider starting out with “Certified Images” As mentioned on Docker Hub, “Official Images” are a curated set of repositories, they provide a base OS, follow best practices for Dockerfile and contain the latest security updates and patches amongst other things. If you are a seasoned veteran of Docker, you could technically use any image you wish, provided you are adept at inspecting the Dockerfile and validating that you aren’t getting any Easter eggs :-D.įor most people I’d highly recommend sticking to Official images. Anyone is allowed to register with Docker Hub and publish images. If you do a quick search on Docker Hub for a container image, your search may throw up a couple of results. But what is an “Official” docker image? Official Docker Image So now, how do you choose? One rule of thumb I use is to keep my Dockerfile as lean as possible and find an official base image as close to what I require to run my application. This Java base image will automatically include Linux, much like the way Maven dependencies work. Alternately, I could save myself the work of manually installing Java and use a Java base image to run my application. Each step we use to install custom software / utilities will create another layer. For our simple java application here, we could start off with Linux as a base image, then install java and the related dependencies onto it. One of the most important concepts you need to understand with docker images is the concept of layering. The official Docker documentation describes a container image as “a lightweight, standalone, executable package of software that includes everything needed to run an application: code, runtime, system tools, system libraries and settings.” The only thing this simple application does is print “Hello Docker!!”. The entire source code may be found here. I have packaged my simple java application using the Maven shade plugin to build an executable jar. Running a Spring Boot REST Application with Docker.Familiarity with basic Docker commands and concepts.Familiarity with packaging Java applications as an executable uber/fat jar. In this post I will go over the most important concepts you need to know in order to run your Java applications within Docker containers in a production environment. Hopefully you are here because you are convinced that you want to use Docker to run your Java / JVM application.
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