Container states (created, running, paused, stopped) in Docker - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to list all containers, including those not running.

Docker

docker ps [1]

Drag options to blanks, or click blank then click option'

A-a

B-l

C-s

D-r

Attempts:

3 left

💡 Hint

Common Mistakes

Using -l shows only the last container.

Using -r is not valid. -s shows sizes but only for running containers.

The -a option shows all containers, including created, stopped, and paused ones.

2fill in blank

medium

Complete the command to pause a running container named 'webapp'.

Docker

docker [1] webapp

Drag options to blanks, or click blank then click option'

Arestart

Bstop

Ckill

Dpause

Attempts:

3 left

💡 Hint

Common Mistakes

Using stop will stop the container, not pause it.

Using kill will forcefully stop the container.

The pause command suspends all processes in the container without stopping it.

3fill in blank

hard

Fix the error in the command to start a container with ID 'abc123'.

Docker

docker [1] abc123

Drag options to blanks, or click blank then click option'

Astart

Brun

Ccreate

Dexec

Attempts:

3 left

💡 Hint

Common Mistakes

Using run creates a new container instead of starting the existing one.

Using exec runs a command inside a running container.

The start command resumes a stopped container. run creates and starts a new container, which is different.

4fill in blank

hard

Fill both blanks to create a container named 'db' from the image 'mysql' and keep it stopped after creation.

Docker

docker [1] --name [2] mysql

Drag options to blanks, or click blank then click option'

Acreate

Brun

Cdb

Dstart

Attempts:

3 left

💡 Hint

Common Mistakes

Using run starts the container immediately.

Using start or db as commands is incorrect.

The create command makes a container but does not start it. The name 'db' is assigned with --name.

5fill in blank

hard

Fill both blanks to unpause a container named 'cache' and then stop it.

Docker

docker [1] cache && docker [2] cache

Drag options to blanks, or click blank then click option'

Aunpause

Bstop

Cpause

Dstart

Attempts:

3 left

💡 Hint

Common Mistakes

Using pause instead of unpause to resume.

Using start instead of unpause for resuming a paused container.

The unpause command resumes the paused container, making it running. The stop command stops it. pause suspends a running container, and start resumes a stopped one.

Practice

1. Which Docker container state means the container is currently executing processes?

easy

A. stopped

B. created

C. paused

D. running

Solution

1. Step 1: Understand container states

   The 'running' state means the container is actively executing its processes.

2. Step 2: Compare other states

   'Created' means container is made but not started, 'paused' means temporarily halted, 'stopped' means container is not running.

3. Final Answer:

   running -> Option D

4. Quick Check:

   Active container = running [OK]

Hint: Running means container is actively working [OK]

Common Mistakes:

• Confusing 'created' with 'running'
• Thinking 'paused' means running
• Mixing 'stopped' with 'running'

2. Which command shows all Docker containers including stopped ones?

easy

A. docker ps -a

B. docker pause

C. docker start

D. docker ps

Solution

1. Step 1: Recall docker ps usage

   'docker ps' shows only running containers by default.

2. Step 2: Use option to show all containers

   'docker ps -a' lists all containers, including stopped and paused ones.

3. Final Answer:

   docker ps -a -> Option A

4. Quick Check:

   Show all containers = docker ps -a [OK]

Hint: Add -a to see all containers, not just running [OK]

Common Mistakes:

• Using 'docker ps' alone shows only running containers
• Confusing 'docker start' with listing containers
• Thinking 'docker pause' lists containers

3. What is the state of the container after running these commands?

docker create nginx
docker start <container_id>
docker pause <container_id>

medium

A. paused

B. created

C. running

D. stopped

Solution

1. Step 1: Analyze commands sequence

   'docker create' makes container in 'created' state, 'docker start' moves it to 'running'.

2. Step 2: Effect of 'docker pause'

   'docker pause' suspends container processes without stopping it, changing state to 'paused'.

3. Final Answer:

   paused -> Option A

4. Quick Check:

   Pause command sets state to paused [OK]

Hint: Pause command changes running to paused state [OK]

Common Mistakes:

• Assuming container stays running after pause
• Confusing created with paused
• Thinking pause stops the container

4. You ran docker pause mycontainer but got an error saying container is not running. What is the likely cause?

medium

A. Container is already paused

B. Container is stopped or not started

C. Container name is incorrect

D. Docker daemon is not running

Solution

1. Step 1: Understand pause command requirements

   'docker pause' only works on running containers to suspend them temporarily.

2. Step 2: Interpret error message

   Error about container not running means it is stopped or never started, so pause cannot apply.

3. Final Answer:

   Container is stopped or not started -> Option B

4. Quick Check:

   Pause needs running container [OK]

Hint: Pause only works on running containers [OK]

Common Mistakes:

• Trying to pause stopped containers
• Ignoring container state before pausing
• Assuming pause works on any container

5. You want to temporarily stop a container without losing its state and then resume it later. Which sequence of commands should you use?

hard

A. docker kill <container_id> then docker start <container_id>

B. docker stop <container_id> then docker start <container_id>

C. docker pause <container_id> then docker unpause <container_id>

D. docker restart <container_id> then docker pause <container_id>

Solution

1. Step 1: Understand stopping vs pausing

   'docker stop' stops container and loses running state; 'docker pause' suspends without stopping.

2. Step 2: Identify commands to pause and resume

   'docker pause' suspends container, 'docker unpause' resumes it preserving state.

3. Final Answer:

   docker pause & docker unpause -> Option C

4. Quick Check:

   Pause/unpause = temporary stop and resume [OK]

Hint: Pause to stop temporarily, unpause to resume [OK]

Common Mistakes:

• Using stop loses container state
• Confusing kill with pause
• Restarting instead of unpausing