Explanation of Dockerfile Code Line by Line DevOps Engineer Mock Interview Questions & Answers #aws

This transcript explains the process of building a Docker image through a Dockerfile, step by step. It covers the purpose of different commands in the Dockerfile, like setting the base image, working directory, installing dependencies, and exposing a port. It culminates in understanding how to execute the application upon container startup.

Dockerfile Commands

• 00:00:13 The Dockerfile begins by pulling a base image ('14') and setting the working directory within the container. It then copies 'package.json' and 'package-lock.json' into the working directory before using the 'RUN' command to install dependencies from a package manager. The remaining application code is copied, and the port '3000' is exposed.

Container Execution

• 00:01:51 The 'CMD' instruction is utilized to specify the command to start the application when the container is run. It explains that this command can be used to replace packages or statements within the target location while the container is running. The 'EXPOSE' command's role is to inform Docker that the container listens on a specific port, in this case, '3000', to allow access to the application.