Containers vs virtual machines in Docker - Practice Questions

Challenge - 5 Problems

🧠 Conceptual

intermediate

Difference in resource usage between containers and VMs

Which statement best describes the difference in resource usage between containers and virtual machines?

A Virtual machines share the host OS kernel and use fewer resources than containers, which run full guest OS instances.

B Virtual machines do not require any resources because they run on the host OS directly.

C Containers and virtual machines use the same amount of resources because both run full guest OS instances.

D Containers share the host OS kernel and use fewer resources than virtual machines, which run full guest OS instances.

💡 Hint

Think about what runs inside containers versus virtual machines.

Containers share the host OS kernel, so they are lightweight and use fewer resources. Virtual machines run a full guest OS, which requires more resources.

💻 Command Output

intermediate

Output of Docker command showing running containers

What is the output of the command docker ps when no containers are running?

Docker

docker ps

A CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES\nabc123 nginx "/bin/bash" 2 hours ago Up 2 hours 80/tcp webserver

B CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

C Error: No containers found

D No containers running

💡 Hint

Try running docker ps on a system with no running containers.

The docker ps command always shows the header line even if no containers are running. It does not print an error or message.

🔀 Workflow

advanced

Steps to migrate an application from VM to container

Which sequence correctly describes the steps to migrate an application from a virtual machine to a Docker container?

A 3,2,1,4

B 2,1,3,4

C 1,2,3,4

D 1,3,2,4

💡 Hint

Think about the logical order from understanding the app to deployment.

First, identify dependencies, then write the Dockerfile, build the image, and finally test and deploy.

❓ Troubleshoot

advanced

Troubleshooting container networking issues

You have a container running a web server, but you cannot access it from your host machine. Which is the most likely cause?

A The container port is not published to the host using <code>-p</code> option.

B The container image is missing the web server software.

C The Docker daemon is not running on the host.

D The container is running in privileged mode.

💡 Hint

Check how ports are exposed from container to host.

If the container port is not published to the host, the host cannot access the service inside the container.

✅ Best Practice

expert

Best practice for container image size optimization

Which practice is best to minimize the size of a Docker container image?

A Use a minimal base image and remove unnecessary files during build.

B Install all development tools inside the container for flexibility.

C Use multiple layers with large files to speed up builds.

D Keep all logs inside the container to track issues.

💡 Hint

Think about what makes images large and how to reduce that.

Using a minimal base image and cleaning up unnecessary files reduces image size and improves performance.