Dockerfile Debugging Basics

Now that we’ve covered Building and Using Docker Containers and Images, you can build an image and start a container.

The next skill is figuring out what went wrong when Docker says no.

A Dockerfile is a recipe, and debugging it means asking one precise question at a time:

Did the failure happen while building the image?
             or
Did the image build, but the container failed when it ran?

That split matters because the tools are different:

• Build failure: inspect docker build output, build context, COPY, RUN, cache, and layers.
• Runtime failure: inspect docker run, logs, environment variables, entrypoint, command, and files inside the container.

This lesson is a practical debugging loop you can use locally before a broken Dockerfile wastes CI/CD time.