Question 1

What is the difference between an Image and a Container?

Accepted Answer

An **Image** is a read-only template used to create containers. It contains the application code, libraries, and dependencies. A **Container** is a running instance of an image. You can have many containers running from a single image.

Question 2

Explain the difference between COPY and ADD instructions in a Dockerfile.

Accepted Answer

`COPY` and `ADD` both copy files from the host into the image. However, `ADD` can also download files from URLs and automatically extract tar files. `COPY` is generally preferred for its simplicity and transparency.

Question 3

What is Multi-stage build and why is it useful?

Accepted Answer

Multi-stage builds allow you to use multiple `FROM` statements in a single Dockerfile. You can compile code in one stage and then copy only the final binary into a smaller, production-ready stage. This significantly reduces the final image size.

Question 4

What is the difference between a CMD and ENTRYPOINT instruction?

Accepted Answer

`ENTRYPOINT` sets the primary command for the container, which cannot be easily overridden (but can be appended to). `CMD` provides default arguments for the entrypoint or a default command that is easily overridden if the user specifies one in `docker run`.

Docker Top Q&A

What is the difference between an Image and a Container?

Explain the difference between COPY and ADD instructions in a Dockerfile.

What is Multi-stage build and why is it useful?

What is the difference between a CMD and ENTRYPOINT instruction?

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