Docker basics review in Microservices - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the base image in a Dockerfile.

Microservices

FROM [1]

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

ACOPY . /app

BRUN apt-get update

Cubuntu:latest

DEXPOSE 80

Attempts:

3 left

💡 Hint

Common Mistakes

Using RUN or COPY instead of a base image after FROM.

The FROM instruction sets the base image for the Dockerfile. Here, ubuntu:latest is a valid base image.

2fill in blank

medium

Complete the Dockerfile command to copy files from the host to the container.

Microservices

COPY [1] /app

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

A/app

B.

CRUN apt-get install

DEXPOSE 8080

Attempts:

3 left

💡 Hint

Common Mistakes

Using container paths as source instead of host paths.

The COPY command copies files from the current directory . on the host to the /app directory in the container.

3fill in blank

hard

Fix the error in the Dockerfile command to expose a port.

Microservices

EXPOSE [1]

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

A80

Beighty

Cport 80

D8080/tcp

Attempts:

3 left

💡 Hint

Common Mistakes

Writing port names or including protocol in EXPOSE command.

The EXPOSE command expects a port number as an integer, like 80. Text or extra words cause errors.

4fill in blank

hard

Fill both blanks to run a command and set the working directory in a Dockerfile.

Microservices

WORKDIR [1]
RUN [2]

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

A/app

Bnpm install

Capt-get update

D/usr/src/app

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong directory paths or commands that don't install dependencies.

WORKDIR /usr/src/app sets the working directory. RUN npm install runs the install command inside the container.

5fill in blank

hard

Fill all three blanks to define environment variables, expose a port, and specify the command to run.

Microservices

ENV [1]=[2]
EXPOSE [3]
CMD ["node", "server.js"]

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

ANODE_ENV

Bproduction

C3000

Ddevelopment

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong environment variable names or invalid port numbers.

ENV NODE_ENV=production sets an environment variable. EXPOSE 3000 opens port 3000. CMD runs the node server.

Practice

1. What is the main purpose of Docker in microservices architecture?

easy

A. To replace the need for servers entirely

B. To write application code faster

C. To package applications with all dependencies for consistent deployment

D. To monitor network traffic between services

Solution

1. Step 1: Understand Docker's role

   Docker packages applications with their dependencies to ensure they run the same everywhere.

2. Step 2: Compare options

   Only To package applications with all dependencies for consistent deployment describes packaging apps with dependencies; others describe unrelated tasks.

3. Final Answer:

   To package applications with all dependencies for consistent deployment -> Option C

4. Quick Check:

   Docker packages apps = B [OK]

Hint: Docker bundles apps and dependencies for consistent runs [OK]

Common Mistakes:

• Thinking Docker replaces servers
• Confusing Docker with coding tools
• Assuming Docker monitors network

2. Which Docker command is used to create a new image from a Dockerfile?

easy

A. docker run

B. docker start

C. docker push

D. docker build

Solution

1. Step 1: Identify command purpose

   docker build creates an image from a Dockerfile.

2. Step 2: Eliminate other commands

   docker run starts containers, docker start restarts stopped containers, docker push uploads images to a registry.

3. Final Answer:

   docker build -> Option D

4. Quick Check:

   Build = create image [OK]

Hint: Build creates images; run starts containers [OK]

Common Mistakes:

• Using docker run to create images
• Confusing docker start with build
• Thinking docker push creates images

3. Given this Docker command sequence, what happens?

docker build -t myapp .
docker run -d --name app1 myapp

medium

A. Builds an image named myapp and runs it detached as container app1

B. Runs a container named myapp and builds app1 image

C. Builds a container named myapp and runs it interactively

D. Fails because -d and --name cannot be used together

Solution

1. Step 1: Analyze docker build command

   docker build -t myapp . creates an image tagged 'myapp' from current directory.

2. Step 2: Analyze docker run command

   docker run -d --name app1 myapp runs container named 'app1' in detached mode from image 'myapp'.

3. Final Answer:

   Builds an image named myapp and runs it detached as container app1 -> Option A

4. Quick Check:

   Build image then run container detached = A [OK]

Hint: Build tags image; run starts container with name and mode [OK]

Common Mistakes:

• Mixing image and container names
• Thinking -d disables naming
• Confusing build and run order

4. Identify the error in this Docker command:

docker run --name mycontainer -p 8080 myimage

medium

A. Port mapping syntax is incomplete

B. Missing container name

C. Image name is missing

D. Cannot use -p with --name

Solution

1. Step 1: Check port mapping syntax

   -p 8080 is incomplete; it should specify host and container ports like -p 8080:80.

2. Step 2: Verify other parts

   Container name and image name are present; no restriction on using -p with --name.

3. Final Answer:

   Port mapping syntax is incomplete -> Option A

4. Quick Check:

   Port mapping needs host:container format [OK]

Hint: Port mapping needs host:container format [OK]

Common Mistakes:

• Omitting container port in -p
• Assuming image name is missing
• Thinking -p and --name conflict

5. You want to deploy multiple microservices using Docker containers on one host. Which approach best ensures isolation and easy management?

hard

A. Run all microservices inside a single container

B. Use separate containers for each microservice with individual Dockerfiles

C. Install all microservices directly on the host OS without containers

D. Use one container per microservice but share the same network and volumes without isolation

Solution

1. Step 1: Understand container isolation

   Each microservice should run in its own container for isolation and independent management.

2. Step 2: Evaluate options

   Use separate containers for each microservice with individual Dockerfiles uses separate containers with individual Dockerfiles, enabling isolation and scalability. Run all microservices inside a single container mixes services, reducing isolation. Install all microservices directly on the host OS without containers lacks container benefits. Use one container per microservice but share the same network and volumes without isolation shares resources without isolation.

3. Final Answer:

   Use separate containers for each microservice with individual Dockerfiles -> Option B

4. Quick Check:

   Separate containers = isolation + management [OK]

Hint: One container per microservice for isolation and scaling [OK]

Common Mistakes:

• Running all services in one container
• Skipping containers and installing on host
• Sharing networks and volumes without isolation