Docker engine and runtime - Mini Project: Build & Apply

Docker Engine and Runtime Basics

📖 Scenario: You are starting to learn Docker, a tool that helps you run applications inside small, isolated containers. These containers use the Docker Engine and runtime to work smoothly on your computer.Imagine you want to run a simple web server inside a Docker container to understand how Docker Engine manages containers and images.

🎯 Goal: Build a simple Docker setup where you create a Dockerfile, configure a basic web server image, run a container from it, and check the container status using Docker Engine commands.

📋 What You'll Learn

Create a Dockerfile with a base image and a command to run a web server

Add a configuration variable for the container name

Write the Docker command to build the image and run the container with the specified name

Use Docker Engine commands to list running containers and show the container logs

💡 Why This Matters

🌍 Real World

Docker Engine and runtime are used daily by developers and system administrators to package applications and run them consistently across different computers.

💼 Career

Understanding Docker basics is essential for roles like DevOps engineer, system administrator, and backend developer to manage application deployment and scaling.

1

Create a Dockerfile with a base image and command

Create a file named Dockerfile with these exact contents:
FROM nginx:alpine
CMD ["nginx", "-g", "daemon off;"]

Docker

# Create a Dockerfile with FROM nginx:alpine and CMD ["nginx", "-g", "daemon off;"]

Hint

The Dockerfile must start with FROM nginx:alpine and use CMD ["nginx", "-g", "daemon off;"] to keep the server running.

2

Add a container name variable

Create a variable called container_name and set it to the string my_nginx.

Docker

FROM nginx:alpine
CMD ["nginx", "-g", "daemon off;"]

# Create a variable container_name with value 'my_nginx'
# Your code here

Hint

Just write container_name = "my_nginx" below the Dockerfile content.

3

Build the Docker image and run the container

Write the exact Docker commands to build an image named nginx_image from the Dockerfile and run a container with the name stored in container_name in detached mode.

Docker

container_name = "my_nginx"

# Build the image named nginx_image
# Run the container with name my_nginx in detached mode
# Your code here

Hint

Use docker build -t nginx_image . to build and docker run -d --name my_nginx nginx_image to run the container.

4

Check running containers and view logs

Write the Docker commands to list all running containers and then show the logs of the container named my_nginx.

Docker

# List running containers
# Show logs of container my_nginx
# Your code here

Hint

Use docker ps to list running containers and docker logs my_nginx to see the container logs.

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