Why containers matter in Docker - Challenge Your Understanding

Challenge - 5 Problems

🧠 Conceptual

intermediate

Why do containers improve software deployment?

Which of the following best explains why containers improve software deployment?

A Containers automatically fix bugs in the application code during deployment.

B Containers replace the need for any testing before deployment.

C Containers package an application with its dependencies, ensuring it runs the same everywhere.

D Containers increase the size of applications to make them more secure.

💡 Hint

Think about how containers handle the environment and dependencies.

Containers bundle the app and all its dependencies, so it runs consistently on any system with container support.

💻 Command Output

intermediate

Output of running a container with a simple command

What is the output of this Docker command?

Docker

docker run --rm alpine echo Hello, Containers!

A Hello, Containers!

B Error: alpine image not found

C Container started but no output

D Hello Containers (without comma)

💡 Hint

Consider what the echo command does inside the container.

The command runs the alpine container, executes echo Hello, Containers!, and prints the exact string.

🔀 Workflow

advanced

Order the steps to create and run a container from a Dockerfile

Put these steps in the correct order to build and run a Docker container from a Dockerfile.

A 3,2,1,4

B 2,1,3,4

C 1,3,2,4

D 1,2,3,4

💡 Hint

Think about writing the instructions first, then building, then running.

You first write the Dockerfile, then build an image from it, then run a container from that image, and finally test the container.

❓ Troubleshoot

advanced

Why does this container fail to start?

You run docker run myapp but the container stops immediately. What is the most likely reason?

A The image 'myapp' does not exist locally or remotely.

B The container's main process exited immediately because it has nothing to keep it running.

C The container is running but Docker CLI is not showing it.

D Docker daemon is not installed on the host machine.

💡 Hint

Think about what keeps a container running after it starts.

Containers stop when their main process ends. If the app exits immediately, the container stops too.

✅ Best Practice

expert

Choosing container base images for security and size

Which base image choice is best for a small, secure container for a simple web app?

A Use 'alpine' base image because it is minimal and reduces attack surface.

B Use 'debian' base image because it is the largest and most complete.

C Use 'ubuntu' base image because it has many tools pre-installed.

D Use 'scratch' base image without any OS files for maximum size.

💡 Hint

Consider image size and security risks from extra software.

Alpine is a minimal Linux image, small and with fewer packages, reducing vulnerabilities and size.