netwyman

A Linux container is a set of one or more processes that are isolated from the rest of the system. All the files necessary to run them are provided from a distinct image, meaning that Linux containers are portable and consistent as they move from development, to testing, and finally to production. This makes them much quicker than development pipelines that rely on replicating traditional testing environments. Linux containers are technologies that allow you to package and isolate applications with their entire runtime environment for all of the files necessary to run. This makes it easy to move the contained application between environments (dev, test, production, etc.) while retaining full functionality. Containers are also an important part of IT security. By building security into the container pipeline and defending your infrastructure, you can make sure your containers are reliable, scalable, and trusted. Containers behave like a virtual machine. To the outside world, they can...

Some Docker instructions look similar and cause confusion among developers who just started using Docker or do it irregularly. In this post I will explain the difference between CMD, RUN, and ENTRYPOINT on examples. In a nutshell RUN executes command(s) in a new layer and creates a new image. E.g., it is often used for installing software packages. CMD sets default command and/or parameters, which can be overwritten from command line when docker container runs. ENTRYPOINT configures a container that will run as an executable. If it doesn’t make much sense or you after details, then read on. Docker images and layers When Docker runs a container, it runs an image inside it. This image is usually built by executing Docker instructions, which add layers on top of existing image or OS distribution. OS distribution is the initial image and every added layer creates a new image. Final Docker image reminds an onion with OS distribution inside and a number of layers on top of it. For ex...