What is the purpose of a Dockerfile?

The purpose of a Dockerfile is to automate the creation of a Docker image. A Dockerfile is essentially a set of instructions that Docker uses to build an image. It contains the steps required to assemble the image, including specifying a base image, running commands, copying files, and setting environment variables. This automation means that developers can define the environment their applications will run in with repeatability and without manual intervention.

Using a Dockerfile streamlines the process of deploying applications, fosters consistency across different environments, and simplifies version control of the application environment. When the build process is initiated, Docker reads the Dockerfile line by line to create the final image, which can then be used to run containers.

The other options refer to different aspects of Docker management, but they do not capture the specific function of a Dockerfile. For example, managing Docker containers pertains to runtime operations, while defining services and networks relates to Docker Compose, which is a tool designed for multi-container Docker applications. Monitoring resource usage of containers involves other tools and does not relate to the functionality of a Dockerfile.