Custom config in Docker in Nginx - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the Docker command to run an nginx container with a custom config file.

Nginx

docker run -d -p 8080:80 -v ./mynginx.conf:/etc/nginx/nginx.conf:[1] nginx

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

Arw

Bcache

Ctmpfs

Dro

Attempts:

3 left

💡 Hint

Common Mistakes

Using :rw allows writing to the config file inside the container, which is usually not needed.

Using :tmpfs or :cache are not valid for mounting regular files.

The :ro option mounts the config file as read-only inside the container, which is a common practice for config files.

2fill in blank

medium

Complete the Dockerfile line to copy a custom nginx config into the image.

Nginx

COPY [1] /etc/nginx/nginx.conf

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

Anginx.conf.default

Bdefault.conf

Cmynginx.conf

Dconf.d/nginx.conf

Attempts:

3 left

💡 Hint

Common Mistakes

Using default or unrelated config filenames that do not exist in the build context.

Copying a directory instead of a single config file.

The source file mynginx.conf is copied into the image as the main nginx config.

3fill in blank

hard

Fix the error in the Docker run command to mount a directory with custom configs.

Nginx

docker run -d -p 8080:80 -v [1]:/etc/nginx/conf.d nginx

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

A./conf.d

Bconf.d

C/conf.d

D/etc/nginx/conf.d

Attempts:

3 left

💡 Hint

Common Mistakes

Using just 'conf.d' without './' may cause Docker to look in the wrong place.

Using container paths as source paths causes errors.

The local directory ./conf.d must be relative or absolute path on the host to mount correctly.

4fill in blank

hard

Fill both blanks to create a Dockerfile snippet that sets the working directory and copies the config.

Nginx

WORKDIR [1]
COPY [2] ./

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

A/etc/nginx

Bmynginx.conf

C/usr/share/nginx/html

Ddefault.conf

Attempts:

3 left

💡 Hint

Common Mistakes

Setting working directory to the wrong path.

Copying the wrong config filename.

Setting /etc/nginx as working directory and copying mynginx.conf there places the config correctly.

5fill in blank

hard

Fill all three blanks to define a volume for nginx logs and expose port 80 in Docker Compose.

Nginx

version: '3'
services:
  web:
    image: nginx
    ports:
      - '[1]:80'
    volumes:
      - '[2]:/var/log/nginx'
    restart: [3]

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

A8080

Bnginx-logs

Calways

D80

Attempts:

3 left

💡 Hint

Common Mistakes

Using port 80 on host may conflict with existing services.

Forgetting to define a restart policy causes container to stop on failure.

Port 8080 is mapped to container port 80, volume nginx-logs stores logs, and restart policy always keeps the container running.

Practice

1. What is the main purpose of using a custom nginx configuration file in a Docker container?

easy

A. To install new software packages in the container

B. To change the Docker image version

C. To control how nginx behaves inside the container

D. To update the operating system inside the container

Solution

1. Step 1: Understand nginx configuration role

   The nginx config file controls server behavior like ports, routes, and security.

2. Step 2: Relate config to Docker container

   Using a custom config lets you set nginx behavior inside the container environment.

3. Final Answer:

   To control how nginx behaves inside the container -> Option C

4. Quick Check:

   Custom config controls nginx behavior [OK]

Hint: Custom config changes nginx inside container, not Docker itself [OK]

Common Mistakes:

• Confusing Docker image version with nginx config
• Thinking config updates OS or installs software
• Assuming config changes Docker runtime

2. Which Docker command option is used to mount a custom nginx config file into the container?

easy

A. -v

B. -p

C. -e

D. -d

Solution

1. Step 1: Identify Docker option for mounting files

   The -v option mounts a file or directory from host to container.

2. Step 2: Confirm usage for nginx config

   Mounting the nginx config file uses -v to link host config to container path.

3. Final Answer:

   -v -> Option A

4. Quick Check:

   Mount config file with -v [OK]

Hint: Use -v to mount files or folders into containers [OK]

Common Mistakes:

• Using -p which is for port mapping
• Using -e which sets environment variables
• Using -d which runs container detached

3. Given this Docker run command:

docker run -d -p 8080:80 -v /home/user/nginx.conf:/etc/nginx/nginx.conf:ro nginx

What will happen when you access http://localhost:8080?

medium

A. nginx will use the custom config from /home/user/nginx.conf

B. nginx will use the default config inside the container

C. The container will fail to start due to missing config

D. Port 80 inside container is not exposed

Solution

1. Step 1: Analyze volume mount

   The command mounts host file /home/user/nginx.conf to container path /etc/nginx/nginx.conf as read-only.

2. Step 2: Analyze port mapping and nginx behavior

   Port 8080 on host maps to port 80 in container, nginx uses the mounted config file.

3. Final Answer:

   nginx will use the custom config from /home/user/nginx.conf -> Option A

4. Quick Check:

   Mounted config file is used by nginx [OK]

Hint: Mounted config overrides default inside container [OK]

Common Mistakes:

• Assuming default config is used despite mounting
• Thinking container fails without explicit start error
• Confusing port mapping direction

4. You run this command but nginx inside the container fails to start:

docker run -d -p 8080:80 -v /home/user/nginx.conf:/etc/nginx/nginx.conf nginx

What is the most likely cause?

medium

A. The port 8080 is already in use on host

B. The nginx.conf file has syntax errors

C. The volume mount path is incorrect

D. The Docker image name is wrong

Solution

1. Step 1: Check common nginx start failure reasons

   nginx fails to start if config file has syntax errors or is missing.

2. Step 2: Analyze given command and symptoms

   Volume mount looks correct, port mapping is standard, image name is valid. Syntax errors in config are common cause.

3. Final Answer:

   The nginx.conf file has syntax errors -> Option B

4. Quick Check:

   Syntax errors cause nginx start failure [OK]

Hint: Always test nginx config syntax before running container [OK]

Common Mistakes:

• Blaming port conflict without error message
• Assuming volume mount path is wrong without checking
• Thinking image name is incorrect without error

5. You want to run nginx in Docker with a custom config file and ensure the container reloads nginx if the config changes on the host. Which approach is best?

hard

A. Mount the config file with -v and restart the container manually after changes

B. Use environment variables to pass config settings instead of a file

C. Copy the config file into the image during build and rebuild image on changes

D. Mount the config file with -v and use a file watcher inside container to reload nginx

Solution

1. Step 1: Understand config update needs

   To reload nginx on config changes without restarting container, nginx must reload config dynamically.

2. Step 2: Evaluate options for dynamic reload

   Mounting config with -v allows live changes. Using a file watcher inside container can trigger nginx reload on changes.

3. Step 3: Compare other options

   Manual restart is less efficient, copying config requires rebuild, env vars don't replace full config file.

4. Final Answer:

   Mount the config file with -v and use a file watcher inside container to reload nginx -> Option D

5. Quick Check:

   File watcher + mounted config enables live reload [OK]

Hint: Use mounted config plus watcher to reload nginx automatically [OK]

Common Mistakes:

• Rebuilding image for every config change
• Restarting container manually each time
• Trying to replace config with environment variables