Question 1

What is a Dockerfile?

Accepted Answer

A Dockerfile is a text file containing instructions that Docker uses to build a container image. It defines the base image, application code, dependencies, and runtime configuration needed to run your application in an isolated container.

Question 2

What is a multi-stage Docker build?

Accepted Answer

A multi-stage build uses multiple FROM statements in a single Dockerfile. The build stage installs dependencies and compiles code, while the production stage copies only the final artifacts. This results in significantly smaller, more secure images.

Question 3

Why should I use a non-root user in my Dockerfile?

Accepted Answer

Running containers as root is a security risk. If an attacker exploits your application, they gain root access to the container. Using a non-root user limits their permissions and follows the principle of least privilege.

Question 4

What is a .dockerignore file?

Accepted Answer

A .dockerignore file tells Docker which files and directories to exclude from the build context. This speeds up builds, reduces image size, and prevents sensitive files like .env or node_modules from being copied into the image.

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