Official Nginx Docker image - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Nginx container startup log

You run the command docker run --name webserver -d nginx. What is the expected output of docker logs webserver?

A nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)

B

2024/01/01 00:00:00 [notice] 1#1: using the "epoll" event method
2024/01/01 00:00:00 [notice] 1#1: nginx/1.25.0
2024/01/01 00:00:00 [notice] 1#1: start worker processes
2024/01/01 00:00:00 [notice] 1#1: start worker process 7

C

Error: Cannot find image 'nginx:latest' locally
Pulling from library/nginx
Digest: sha256:abcdef1234567890
Status: Downloaded newer image for nginx:latest

D docker: command not found

💡 Hint

Check the typical startup log messages for the official Nginx container.

When the Nginx container starts successfully, it logs notices about the event method, version, and worker processes starting. Option B shows this typical log output. Option B shows image pull messages, not logs. Option B is an error if port 80 is busy. Option B is a shell error.

❓ Configuration

intermediate

Mounting custom Nginx config in Docker

You want to run the official Nginx Docker container with your own nginx.conf file located at /home/user/nginx.conf. Which docker run command correctly mounts this config to override the default?

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

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

C docker run -d -p 80:80 -v /home/user/nginx.conf:/usr/local/nginx/conf/nginx.conf:ro nginx

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

💡 Hint

The official Nginx image expects the main config at /etc/nginx/nginx.conf.

The official Nginx Docker image uses /etc/nginx/nginx.conf as the main config file. Mounting your custom config there overrides the default. Option D correctly mounts the file read-only. Option D reverses source and target. Option D uses a wrong path. Option D mounts to conf.d directory which expects snippets, not the main config.

❓ Troubleshoot

advanced

Nginx container fails to start with port binding error

You run docker run -d -p 80:80 nginx but the container exits immediately. Checking logs shows:
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
What is the most likely cause?

A The Docker daemon is not running

B The container lacks permission to bind to port 80 inside the container

C Another process on the host is already using port 80

D The Docker image is corrupted and missing Nginx binaries

💡 Hint

Port binding errors usually mean the port is busy on the host machine.

The error means the host port 80 is already occupied by another process, so Docker cannot bind it for the container. Option C would cause different errors. Option C is unlikely as containers run as root by default. Option C would prevent any Docker commands from working.

🔀 Workflow

advanced

Updating Nginx container with zero downtime

You have a running Nginx container named webserver. You want to update it to a newer Nginx image version without downtime. Which workflow is best?

A Pull new image, start new container on different ports, switch traffic via load balancer, then stop old container

B Pull new image, stop current container, start new container with same ports and volumes

C Remove old container, pull new image, start new container with same ports

D Restart Docker daemon, then pull new image and start new container

💡 Hint

Zero downtime means traffic must not be interrupted during update.

Option A describes a blue-green deployment approach: run new container on different ports, switch traffic, then stop old container. This avoids downtime. Options A and C cause downtime by stopping old container first. Option A is unrelated.

✅ Best Practice

expert

Securing Nginx Docker container with least privileges

Which practice best improves security by running the official Nginx Docker container with least privileges?

A Use the <code>--user</code> flag to run Nginx as a non-root user inside the container

B Run the container as root user to avoid permission issues

C Disable all logging to prevent sensitive data exposure

D Run the container with <code>--privileged</code> flag for full access

💡 Hint

Running as non-root inside containers is a common security best practice.

Running Nginx as a non-root user inside the container reduces risk if compromised. Option A is insecure. Option A disables useful logs and does not improve privilege. Option A grants excessive privileges, increasing risk.