Building Enterprise JavaScript Applications

Images are layered

An image is an ordered list of layers, where each layer is an operation used to set up the image and container. These operations may include setting/updating system configuration, environment variables, installation of libraries or programs, and so on. These operations are specified inside a Dockerfile. Therefore, every layer corresponds to an instruction in the image’s Dockerfile.

For instance, if we are to generate a Docker image for our backend API, we need it to have the Node ecosystem installed, have our application code copied over, and our application built using yarn. Therefore, our image may have the following layers (lower layers are run first):

• Run yarn run build
• Copy application code inside the image
• Install ...