Verifying installation with docker run hello-world - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of docker run hello-world on a fresh Docker install?

You just installed Docker and ran docker run hello-world. What output should you expect to confirm Docker is working correctly?

Docker

docker run hello-world

A A message starting with 'Hello from Docker!' followed by instructions about Docker installation verification.

B An error message saying 'docker: command not found'.

C A blank screen with no output.

D A message saying 'Cannot connect to the Docker daemon at unix:///var/run/docker.sock'.

💡 Hint

Think about what a successful Docker container run would print to confirm installation.

The 'hello-world' image prints a friendly message starting with 'Hello from Docker!' to confirm Docker is installed and running properly.

❓ Troubleshoot

intermediate

Which error indicates Docker daemon is not running when running docker run hello-world?

You run docker run hello-world but get an error. Which error message means the Docker daemon is not running?

Docker

docker run hello-world

A Error: permission denied while accessing Docker socket.

B Error: image hello-world not found locally and no pull access.

C Error: command not found: docker

D Error: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

💡 Hint

Look for the message about connecting to the Docker daemon.

The error about not connecting to the Docker daemon means the Docker service is not running or accessible.

✅ Best Practice

advanced

What is the best practice to verify Docker installation on a new machine?

After installing Docker, which step is the best practice to verify the installation?

A Restart the machine and check Docker service status only.

B Run <code>docker ps</code> to list running containers immediately after install.

C Run <code>docker run hello-world</code> to test if Docker can pull and run containers.

D Run <code>docker build .</code> in an empty directory.

💡 Hint

Think about a simple command that confirms Docker can run containers.

Running 'docker run hello-world' is the simplest way to confirm Docker is installed, the daemon is running, and containers can be pulled and executed.

🧠 Conceptual

advanced

Why does docker run hello-world download an image on first run?

When you run docker run hello-world for the first time, Docker downloads the image. Why does this happen?

A Because Docker always downloads images even if they exist locally.

B Because the image is not present locally, Docker pulls it from the default registry to run the container.

C Because the hello-world image is built locally every time you run the command.

D Because Docker needs to update the image to the latest version before running.

💡 Hint

Think about how Docker handles images it does not have on your computer.

Docker pulls images from a registry only if they are not found locally to run containers.

🔀 Workflow

expert

What is the correct sequence of steps when verifying Docker installation using docker run hello-world?

Put these steps in the correct order to verify Docker installation using the 'hello-world' image.

A 3,1,4,2

B 1,3,4,2

C 3,4,1,2

D 4,3,1,2

💡 Hint

Think about what must be ready before running the command and what happens during execution.

First, Docker daemon must be running (3). Then you run the command (1). If image missing, Docker pulls it (4). Finally, you check the output (2).