Containerizing an App - The Commands

The summary of commands for containerizing an app

• docker build containerizes applications. It reads a Dockerfile and follows the instructions to create an OCI image. The -t flag tags the image, and the -f flag lets you specify the name and location of the Dockerfile. The build context is where your application files exist and can be a directory on your local Docker host or a remote Git repo.

• The Dockerfile FROM instruction specifies the base image. It’s usually the first instruction in a Dockerfile, and it’s considered a good practice to build from Docker Official Images or images from Verified Publishers. FROM is also used to identify new build stages in multi-stage builds.

• The Dockerfile RUN instruction lets you run commands during a build. It’s commonly used to update packages and install dependencies. Every RUN instruction creates a new image layer.

• The Dockerfile COPY instruction adds files to images, and you’ll regularly use it to copy your application code into a new image. Every COPY instruction creates an image layer.

• The Dockerfile EXPOSE instruction documents an application’s network port.

• The Dockerfile ENTRYPOINT and CMD instructions tell Docker how to run the app when starting a new container.

• Some other Dockerfile instructions include LABEL, ENV, ONBUILD, HEALTHCHECK and more.