Docker engine and runtime - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to start the Docker service.

Docker

sudo systemctl [1] docker

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

Arestart

Bstart

Cstop

Dstatus

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'stop' instead of 'start' stops the service.

Using 'status' only shows the service status but does not start it.

The start command tells systemctl to start the Docker service so it runs in the background.

2fill in blank

medium

Complete the command to check the Docker engine version.

Docker

docker [1] version

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

Arun

Binfo

Cversion

Dps

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'docker info' shows system info but not just the version.

Using 'docker ps' lists running containers, not version.

The docker version command shows the Docker engine and client version details.

3fill in blank

hard

Fix the error in the command to run a container interactively.

Docker

docker run -[1] ubuntu /bin/bash

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

Av

Bd

Cp

Di

Attempts:

3 left

💡 Hint

Common Mistakes

Using '-d' runs the container detached (in background).

Using '-p' is for port mapping, not interactive mode.

The -i flag keeps STDIN open for interactive mode, allowing you to interact with the container.

4fill in blank

hard

Fill both blanks to list all Docker containers including stopped ones.

Docker

docker [1] [2]

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

Aps

B-a

C-l

Dimages

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'docker images' lists images, not containers.

Using '-l' shows only the last created container.

The command docker ps -a lists all containers, including those stopped.

5fill in blank

hard

Fill all three blanks to build a Docker image with a tag from a Dockerfile in the current directory.

Docker

docker [1] -t [2] [3]

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

Abuild

Bmyapp:latest

C.

Drun

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'docker run' instead of 'docker build' tries to run a container.

Forgetting the '.' means Docker won't know where the Dockerfile is.

The command docker build -t myapp:latest . builds an image named 'myapp' with tag 'latest' from the current directory.

Practice

1. What is the primary role of the Docker engine in container management?

easy

A. It manages and controls containers on your system.

B. It builds the Linux kernel for container support.

C. It acts as a cloud service for container hosting.

D. It provides a graphical interface for container design.

Solution

1. Step 1: Understand Docker engine's function

   The Docker engine is the main software that manages containers, including building, running, and controlling them.

2. Step 2: Compare options with this role

   Only It manages and controls containers on your system. correctly states that Docker engine manages and controls containers on your system.

3. Final Answer:

   It manages and controls containers on your system. -> Option A

4. Quick Check:

   Docker engine = container management [OK]

Hint: Docker engine controls containers, not builds kernels or UI [OK]

Common Mistakes:

• Confusing Docker engine with cloud services
• Thinking Docker engine builds the OS kernel
• Assuming Docker engine is a GUI tool

2. Which of the following is the correct command to check the Docker engine version?

easy

A. docker version

B. docker check-version

C. docker show version

D. docker engine info

Solution

1. Step 1: Recall Docker command syntax for version

   The correct command to check Docker engine version is docker version.

2. Step 2: Validate other options

   Options A, B, and C are not valid Docker commands for checking version.

3. Final Answer:

   docker version -> Option A

4. Quick Check:

   Check version command = docker version [OK]

Hint: Use 'docker version' to see engine version quickly [OK]

Common Mistakes:

• Using incorrect command names like 'docker check-version'
• Confusing 'docker info' with version command
• Trying 'docker engine info' which is invalid

3. What will be the output of the command docker ps when no containers are running?

medium

A. Displays an error saying no containers found

B. Lists all containers including stopped ones

C. Shows an empty list with only headers

D. Starts a new container automatically

Solution

1. Step 1: Understand what 'docker ps' shows

   The command docker ps lists running containers only, showing headers even if none are running.

2. Step 2: Analyze output when no containers run

   When no containers run, it shows an empty list with column headers but no container entries.

3. Final Answer:

   Shows an empty list with only headers -> Option C

4. Quick Check:

   docker ps with no containers = empty list [OK]

Hint: 'docker ps' shows running containers; empty if none run [OK]

Common Mistakes:

• Thinking it lists stopped containers too
• Expecting an error message when no containers run
• Assuming it starts containers automatically

4. You run docker run -d nginx but get an error: "Cannot connect to the Docker daemon." What is the likely cause?

medium

A. The container is already running.

B. The nginx image does not exist on Docker Hub.

C. The command syntax is incorrect.

D. Docker daemon is not running on the system.

Solution

1. Step 1: Understand the error message

   "Cannot connect to the Docker daemon" means the Docker engine service (daemon) is not running or accessible.

2. Step 2: Check other options

   Image absence or syntax errors cause different errors; container running does not cause daemon connection errors.

3. Final Answer:

   Docker daemon is not running on the system. -> Option D

4. Quick Check:

   Daemon connection error = daemon not running [OK]

Hint: Daemon errors mean Docker service is stopped or unreachable [OK]

Common Mistakes:

• Assuming image absence causes daemon errors
• Blaming command syntax for daemon connection issues
• Thinking container running causes this error

5. You want to run a container using a runtime other than the default Docker runtime. Which command option lets you specify the runtime?

hard

A. docker run --use-runtime=<runtime_name> <image>

B. docker run --runtime=<runtime_name> <image>

C. docker run --engine=<runtime_name> <image>

D. docker run --container-runtime=<runtime_name> <image>

Solution

1. Step 1: Recall Docker run options for runtime

   The correct option to specify a runtime is --runtime followed by the runtime name.

2. Step 2: Verify other options

   Options A, B, and D are not valid Docker CLI options for runtime selection.

3. Final Answer:

   docker run --runtime=<runtime_name> <image> -> Option B

4. Quick Check:

   Specify runtime with --runtime option [OK]

Hint: Use '--runtime' option to select container runtime [OK]

Common Mistakes:

• Using incorrect flags like --engine or --use-runtime
• Confusing runtime with engine options
• Omitting the runtime option entirely