Starting and stopping containers in Docker - Cheat Sheet & Quick Revision

Recall & Review

beginner

What command starts a Docker container that is already created but stopped?

Use docker start <container_name_or_id> to start a stopped container.

beginner

How do you stop a running Docker container?

Use docker stop <container_name_or_id> to stop a running container gracefully.

intermediate

What is the difference between docker stop and docker kill?

docker stop sends a signal to stop the container gracefully, allowing cleanup. docker kill forces the container to stop immediately.

beginner

How can you start a container and attach to its output in one command?

Use docker run to start a new container and attach to its output immediately.

beginner

What command lists all running containers?

Use docker ps to see all running containers.

Which command starts a stopped Docker container?

A docker stop container_name

B docker start container_name

C docker run container_name

D docker kill container_name

docker start resumes a stopped container. docker run creates and starts a new container.

What does docker stop do?

A Forces immediate container shutdown

B Lists all containers

C Gracefully stops a running container

D Starts a new container

docker stop sends a signal to stop the container gracefully.

How do you see all running containers?

A docker show

B docker ls

C docker list

D docker ps

docker ps lists all running containers.

Which command starts a new container and attaches to it immediately?

A docker run

B docker start

C docker attach

D docker exec

docker run creates and starts a new container and attaches to its output.

What is the effect of docker kill?

A Forces immediate stop of a container

B Gracefully stops a container

C Starts a container

D Removes a container

docker kill forces the container to stop immediately without cleanup.

Explain how to start and stop Docker containers using commands.

Think about commands to resume stopped containers and to stop running ones.

Describe the difference between docker stop and docker kill.

Consider how the container is stopped and if it has time to clean up.

Practice

1. Which command is used to start a container that has been stopped in Docker?

easy

A. docker run <container_name>

B. docker stop <container_name>

C. docker start <container_name>

D. docker restart <container_name>

Solution

1. Step 1: Understand the purpose of docker start

   This command resumes a container that was previously stopped without creating a new one.

2. Step 2: Differentiate from other commands

   docker run creates a new container, docker stop stops a running container, and docker restart stops then starts a container.

3. Final Answer:

   docker start <container_name> -> Option C

4. Quick Check:

   Start stopped container = docker start [OK]

Hint: Use 'docker start' to resume stopped containers fast [OK]

Common Mistakes:

• Confusing 'docker run' with 'docker start'
• Using 'docker stop' to start containers
• Thinking 'docker restart' only starts containers

2. Which of the following is the correct syntax to stop a running Docker container named webapp?

easy

A. docker terminate webapp

B. docker kill webapp

C. docker pause webapp

D. docker stop webapp

Solution

1. Step 1: Identify the command to safely stop a container

   docker stop sends a signal to gracefully stop the container.

2. Step 2: Check other options

   docker kill forcefully stops, docker pause suspends, and docker terminate is invalid.

3. Final Answer:

   docker stop webapp -> Option D

4. Quick Check:

   Stop container safely = docker stop [OK]

Hint: Use 'docker stop' to safely end container processes [OK]

Common Mistakes:

• Using 'docker kill' instead of 'docker stop'
• Confusing 'docker pause' with stopping
• Using non-existent commands like 'docker terminate'

3. What will be the output of the following commands if the container db is currently stopped?

docker start db
docker stop db

medium

A. Container 'db' starts, then stops successfully

B. Error: container 'db' not found

C. Container 'db' remains stopped

D. Container 'db' restarts automatically

Solution

1. Step 1: Analyze docker start db

   This command starts the stopped container named 'db'.

2. Step 2: Analyze docker stop db

   This command stops the running container 'db' safely.

3. Final Answer:

   Container 'db' starts, then stops successfully -> Option A

4. Quick Check:

   Start then stop container = success [OK]

Hint: Start then stop a container runs commands without error [OK]

Common Mistakes:

• Assuming 'docker start' creates a new container
• Expecting errors if container exists
• Thinking container restarts automatically without command

4. You run docker start myapp but get the error: Error response from daemon: No such container: myapp. What is the most likely cause?

medium

A. Docker daemon is not running

B. The container 'myapp' does not exist

C. You need to use docker run instead

D. The container 'myapp' is already running

Solution

1. Step 1: Understand the error message

   The error says 'No such container', meaning 'myapp' is not found in Docker's container list.

2. Step 2: Check other options

   If it was running, 'docker start' would not error; 'docker run' creates new containers but error is about missing container; daemon not running causes different errors.

3. Final Answer:

   The container 'myapp' does not exist -> Option B

4. Quick Check:

   No such container error = container missing [OK]

Hint: Check container existence before starting [OK]

Common Mistakes:

• Assuming container is running when error says missing
• Trying 'docker run' without checking container list
• Ignoring Docker daemon status

5. You want to stop a container named api-server but ensure it has 10 seconds to finish its work before stopping. Which command should you use?

hard

A. docker stop -t 10 api-server

B. docker kill -t 10 api-server

C. docker pause api-server

D. docker stop api-server -timeout 10

Solution

1. Step 1: Understand the timeout option in docker stop

   The -t or --time flag sets seconds to wait before killing the container.

2. Step 2: Evaluate the options

   docker kill does not support -t, docker pause only suspends, and -timeout is invalid syntax.

3. Final Answer:

   docker stop -t 10 api-server -> Option A

4. Quick Check:

   Stop with timeout = docker stop -t [OK]

Hint: Use 'docker stop -t seconds' to allow graceful shutdown [OK]

Common Mistakes:

• Using 'docker kill' with timeout flag
• Using invalid flags like '-timeout'
• Confusing 'pause' with stopping