Container states (created, running, paused, stopped) in Docker - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Identify the container state after creation

You run the command docker create nginx. What is the state of the container immediately after this command?

A created

B running

C paused

D stopped

💡 Hint

Creating a container sets it up but does not start it.

The docker create command sets up a container but does not start it. So the container state is created.

💻 Command Output

intermediate

State of container after running and pausing

You start a container with docker run -d nginx and then pause it with docker pause [container_id]. What is the container's state after pausing?

A running

B created

C stopped

D paused

💡 Hint

Pausing suspends the container's processes temporarily.

After pausing, the container is in the paused state, meaning its processes are suspended but the container is still allocated.

✅ Best Practice

advanced

Choosing the correct command to stop a running container

Which command properly stops a running Docker container and changes its state to 'stopped'?

A docker stop [container_id]

B docker pause [container_id]

C docker kill [container_id]

D docker rm [container_id]

💡 Hint

Stopping allows graceful shutdown, killing is forceful.

docker stop sends a signal to gracefully stop the container, changing its state to stopped. docker kill forcefully terminates it, but the state is still considered stopped. docker pause only suspends the container. docker rm removes the container.

❓ Troubleshoot

advanced

Diagnosing why a container is stuck in 'paused' state

You notice a container is stuck in the 'paused' state and does not resume with docker unpause. What is a likely cause?

A The container was removed while paused

B Docker daemon crashed and did not restore container state

C The container is in 'created' state, not 'paused'

D The container was never started

💡 Hint

Docker daemon manages container states and may lose track after a crash.

If the Docker daemon crashes while a container is paused, it may fail to restore the paused state properly, causing the container to be stuck. The container cannot resume until the daemon is restarted or the container is manually handled.

🧠 Conceptual

expert

Understanding container lifecycle transitions

Which sequence correctly represents the lifecycle states of a Docker container from creation to removal?

A created → paused → running → stopped → removed

B running → created → paused → stopped → removed

C created → running → paused → running → stopped → removed

D created → running → stopped → paused → removed

💡 Hint

Think about the order in which a container can be paused and resumed.

The container lifecycle starts with created, then running when started. It can be paused and then resumed back to running. After stopping, it moves to stopped before removal.