Docker Compose with Nginx - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is Docker Compose used for in the context of Nginx?

Docker Compose is used to define and run multi-container Docker applications, such as running Nginx together with other services like web apps or databases, using a single YAML file.

beginner

In a Docker Compose file, how do you specify the Nginx image to use?

You specify the Nginx image under the service with the key 'image', for example: image: nginx:latest

intermediate

How do you map a local Nginx configuration file into the Nginx container using Docker Compose?

Use the 'volumes' key to map the local config file to the container path, for example: volumes: - ./nginx.conf:/etc/nginx/nginx.conf:ro

beginner

What port does Nginx usually listen on, and how do you expose it in Docker Compose?

Nginx usually listens on port 80. In Docker Compose, expose it by mapping ports like: ports: - "80:80"

beginner

Why is it useful to use Docker Compose with Nginx for local development?

It allows you to easily start, stop, and configure Nginx alongside other services with one command, making development faster and more consistent.

Which key in a Docker Compose file defines the services to run?

A volumes

B containers

C images

D services

The 'services' key lists all the containers to run in Docker Compose.

How do you tell Docker Compose to map port 8080 on your computer to port 80 in the Nginx container?

A ports: - "80:8080"

B ports: - "8080:80"

C expose: 8080:80

D map_ports: 8080->80

The format is 'host_port:container_port', so '8080:80' maps local 8080 to container 80.

What does the ':ro' suffix mean when mounting a volume in Docker Compose?

A Read-only access

B Read and write access

C Remove on exit

D Restart option

':ro' means the volume is mounted as read-only inside the container.

Which command starts all services defined in a Docker Compose file?

A docker compose up

B docker run

C docker start all

D docker build

'docker compose up' starts all services defined in the compose file.

Where is the default Nginx configuration file located inside the container?

A /var/www/html/index.html

B /usr/local/nginx.conf

C /etc/nginx/nginx.conf

D /nginx/config.conf

The default Nginx config file is at '/etc/nginx/nginx.conf' inside the container.

Explain how to set up a basic Docker Compose file to run Nginx serving a static website.

Think about service name, image, ports, and volumes.

Describe the benefits of using Docker Compose with Nginx for managing multiple services.

Focus on convenience and environment consistency.

Practice

1. What is the main purpose of using Docker Compose with Nginx?

easy

A. To replace Nginx with a different web server

B. To run Nginx and other services together easily using a YAML file

C. To write Nginx configuration files in JSON format

D. To compile Nginx from source code automatically

Solution

1. Step 1: Understand Docker Compose role

   Docker Compose helps run multiple services together using a simple YAML file.

2. Step 2: Connect with Nginx usage

   Using Docker Compose with Nginx lets you start Nginx and other needed services easily.

3. Final Answer:

   To run Nginx and other services together easily using a YAML file -> Option B

4. Quick Check:

   Docker Compose + Nginx = easy multi-service setup [OK]

Hint: Docker Compose uses YAML to run multiple services together [OK]

Common Mistakes:

• Thinking Docker Compose changes Nginx config format
• Confusing Docker Compose with Nginx replacement
• Assuming Docker Compose compiles software

2. Which of the following is the correct way to expose port 80 of an Nginx container in a Docker Compose file?

easy

A. publish: 80

B. expose: 80:80

C. ports: - "80:80"

D. port: 80

Solution

1. Step 1: Recall Docker Compose port syntax

   To expose ports, use the 'ports' key with format "hostPort:containerPort" as a list item.

2. Step 2: Match correct syntax

   Only 'ports: - "80:80"' correctly exposes container port 80 to host port 80.

3. Final Answer:

   ports: - "80:80" -> Option C

4. Quick Check:

   Expose ports with 'ports: - "host:container"' [OK]

Hint: Use 'ports: - "hostPort:containerPort"' to expose ports [OK]

Common Mistakes:

• Using 'expose' with port mapping syntax
• Writing 'port' instead of 'ports'
• Using 'publish' which is invalid in Compose

3. Given this Docker Compose snippet, what will happen when you run docker-compose up?

services:
  web:
    image: nginx:latest
    ports:
      - "8080:80"
    volumes:
      - ./site-content:/usr/share/nginx/html:ro

medium

A. Nginx will serve files from /usr/share/nginx/html on port 80 only

B. Nginx will serve default content on port 80

C. Nginx will fail to start due to volume error

D. Nginx will serve files from ./site-content on port 8080

Solution

1. Step 1: Analyze port mapping

   Port 8080 on host maps to port 80 in container, so access via localhost:8080.

2. Step 2: Analyze volume mapping

   Local folder './site-content' is mounted read-only to Nginx's html folder, so custom files are served.

3. Final Answer:

   Nginx will serve files from ./site-content on port 8080 -> Option D

4. Quick Check:

   Port 8080 mapped and volume mounted = custom site served [OK]

Hint: Check ports and volumes to predict container behavior [OK]

Common Mistakes:

• Ignoring port mapping and assuming port 80
• Assuming volume mount fails without error
• Confusing container and host ports

4. You wrote this Docker Compose service for Nginx but after running docker-compose up the container starts but you cannot access Nginx on port 80:

services:
  nginx:
    image: nginx
    ports:
      - "80"
    volumes:
      - ./html:/usr/share/nginx/html

What is the likely cause?

medium

A. Port mapping "80" maps a random host port to container 80; should be "80:80"

B. Volume path './html' does not exist

C. Image name 'nginx' is invalid

D. Missing environment variables for Nginx

Solution

1. Step 1: Check port mapping syntax

   "80" is valid short syntax mapping random host port to container port 80; to bind host port 80 use "80:80".

2. Step 2: Confirm other parts

   Volume path and image name are valid; environment variables are optional for basic Nginx.

3. Final Answer:

   Port mapping "80" maps a random host port to container 80; should be "80:80" -> Option A

4. Quick Check:

   Port mapping must be "hostPort:containerPort" [OK]

Hint: Port mapping needs both host and container ports separated by colon [OK]

Common Mistakes:

• Using single port number without colon
• Assuming volume path error without checking
• Thinking image name 'nginx' is wrong

5. You want to run Nginx with Docker Compose and add a custom configuration file nginx.conf located in your project folder. Which Docker Compose volume setting correctly mounts this file to override the default Nginx config at /etc/nginx/nginx.conf?

hard

A. - ./nginx.conf:/etc/nginx/nginx.conf:ro

B. - ./nginx.conf:/usr/share/nginx/html/nginx.conf

C. - /etc/nginx/nginx.conf:./nginx.conf

D. - ./nginx.conf:/etc/nginx/conf.d/nginx.conf

Solution

1. Step 1: Identify correct Nginx config path

   The main Nginx config file is at /etc/nginx/nginx.conf inside the container.

2. Step 2: Match volume mount syntax

   Mount local nginx.conf to container path with read-only flag ':ro' to override default config safely.

3. Final Answer:

   - ./nginx.conf:/etc/nginx/nginx.conf:ro -> Option A

4. Quick Check:

   Mount local config to /etc/nginx/nginx.conf with ':ro' [OK]

Hint: Mount config file to /etc/nginx/nginx.conf with ':ro' for safety [OK]

Common Mistakes:

• Mounting to wrong container path
• Reversing source and target paths
• Omitting ':ro' for config files