Consistent environments across teams in Docker - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the Dockerfile to specify the base image.

Docker

FROM [1]

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

Aubuntu:latest

Bpython:3.12-slim

Cnode:14-alpine

Dalpine:3.15

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a base image with a different Python version.

Using a non-Python base image.

The base image python:3.12-slim ensures a consistent Python 3.12 environment across teams.

2fill in blank

medium

Complete the Dockerfile to copy the application code into the container.

Docker

COPY [1] /app

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

Aapp/

Bsrc/

C.

Dcode/

Attempts:

3 left

💡 Hint

Common Mistakes

Copying a wrong folder that doesn't contain the app code.

Using an incorrect path that causes build errors.

Using COPY . /app copies the current directory contents into the container's /app folder.

3fill in blank

hard

Fix the error in the Dockerfile command to install dependencies.

Docker

RUN pip install -r [1]

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

Apackages.txt

Brequirements

Cdeps.txt

Drequirements.txt

Attempts:

3 left

💡 Hint

Common Mistakes

Using a filename without extension.

Using a non-standard filename that pip won't recognize.

The standard file for Python dependencies is requirements.txt. Using this ensures pip installs the correct packages.

4fill in blank

hard

Fill both blanks to expose the container port and set the default command.

Docker

EXPOSE [1]
CMD ["[2]"]

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

A8080

Bpython

C5000

Dnode

Attempts:

3 left

💡 Hint

Common Mistakes

Exposing a wrong port that the app doesn't listen on.

Using a command that doesn't start the Python app.

Port 8080 is commonly used for web apps. The command python starts the Python interpreter or script.

5fill in blank

hard

Fill all three blanks to create a Docker Compose service for the app.

Docker

services:
  web:
    image: [1]
    ports:
      - "[2]:[3]"

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

Amyapp:latest

B8080

C80

D5000

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect port mappings that prevent access.

Using an image name without a tag.

The service uses the image myapp:latest. It maps port 8080 on the host to port 80 in the container, a common web port.

Practice

1. Why is Docker useful for maintaining consistent environments across teams?

easy

A. It packages the app and its environment together in a container.

B. It automatically writes code for the team.

C. It replaces the need for version control systems.

D. It runs apps only on Windows machines.

Solution

1. Step 1: Understand Docker container purpose

   Docker containers bundle the app with all its dependencies and environment settings.

2. Step 2: Compare options to Docker's role

   Only the option stating "It packages the app and its environment together in a container." describes packaging app and environment together, ensuring consistency.

3. Final Answer:

   It packages the app and its environment together in a container. -> Option A

4. Quick Check:

   Docker = consistent app environment [OK]

Hint: Docker bundles app + environment for all team members [OK]

Common Mistakes:

• Thinking Docker writes code automatically
• Confusing Docker with version control
• Believing Docker only works on Windows

2. Which of the following is the correct way to start a Docker container named webapp from an image called myapp:latest?

easy

A. docker build webapp myapp:latest

B. docker start myapp:latest webapp

C. docker create webapp myapp:latest

D. docker run --name webapp myapp:latest

Solution

1. Step 1: Recall Docker run syntax

   The command to start a container with a name is: docker run --name [container_name] [image]

2. Step 2: Match the correct command

   docker run --name webapp myapp:latest matches this syntax exactly, starting container 'webapp' from image 'myapp:latest'.

3. Final Answer:

   docker run --name webapp myapp:latest -> Option D

4. Quick Check:

   docker run --name = start container with name [OK]

Hint: Use 'docker run --name' to start named container [OK]

Common Mistakes:

• Using 'docker start' to create container
• Confusing 'docker create' with 'docker run'
• Using 'docker build' to start containers

3. Given this Dockerfile snippet:

FROM python:3.12-slim
WORKDIR /app
COPY . /app
RUN pip install -r requirements.txt
CMD ["python", "app.py"]

What happens when you build and run this Docker image on different team members' machines?

medium

A. The app runs only if all team members have Python installed locally.

B. The app will fail because Python versions differ on each machine.

C. Each team member runs the app in the exact same environment regardless of their OS.

D. The app runs slower on Windows than Linux due to Docker limitations.

Solution

1. Step 1: Analyze Dockerfile purpose

   The Dockerfile sets up a Python 3.12 environment inside a container, independent of host OS.

2. Step 2: Understand container consistency

   Because the container includes Python and dependencies, all team members get the same environment.

3. Final Answer:

   Each team member runs the app in the exact same environment regardless of their OS. -> Option C

4. Quick Check:

   Docker container = consistent environment [OK]

Hint: Dockerfile builds same environment on all machines [OK]

Common Mistakes:

• Assuming local Python is needed
• Believing OS affects container environment
• Thinking Docker slows app on Windows

4. A team member runs docker run myapp but gets an error: Cannot find image 'myapp' locally. What is the likely cause and fix?

medium

A. Docker is not installed; install Docker to fix this.

B. The image 'myapp' is not built locally; run docker build -t myapp . first.

C. The container name is missing; add --name myapp to the command.

D. The Dockerfile is missing; create a Dockerfile to fix this.

Solution

1. Step 1: Understand error meaning

   The error means Docker cannot find the image 'myapp' locally or on Docker Hub.

2. Step 2: Identify fix

   Building the image locally with docker build -t myapp . creates the image for use.

3. Final Answer:

   The image 'myapp' is not built locally; run docker build -t myapp . first. -> Option B

4. Quick Check:

   Image missing? Build it first [OK]

Hint: Build image before running container [OK]

Common Mistakes:

• Thinking Docker is not installed
• Confusing container name with image name
• Assuming Dockerfile absence causes this error

5. Your team wants to ensure everyone uses the same database version inside Docker containers. Which approach best guarantees this consistency?

hard

A. Create a Docker Compose file specifying the exact database image version and share it with the team.

B. Ask each team member to install the database manually on their machine.

C. Use environment variables to let each member choose their preferred database version.

D. Run the database directly on the host OS instead of in Docker.

Solution

1. Step 1: Understand Docker Compose role

   Docker Compose lets you define multi-container setups with exact image versions in one file.

2. Step 2: Evaluate options for consistency

   Sharing a Compose file with fixed database image version ensures all run the same version easily.

3. Step 3: Reject other options

   Manual installs or letting members choose versions cause inconsistency; running on host loses container benefits.

4. Final Answer:

   Create a Docker Compose file specifying the exact database image version and share it with the team. -> Option A

5. Quick Check:

   Compose file = consistent multi-container setup [OK]

Hint: Use Docker Compose with fixed image versions [OK]

Common Mistakes:

• Relying on manual installs for consistency
• Allowing different versions via environment variables
• Running services outside Docker containers