Top 20+ Must‑Know Docker, Nginx, Shell & Jenkins Interview Questions

Preparing for technical interviews? This curated list gathers the most frequently asked questions on Docker, Nginx, Shell scripting, and Jenkins, giving candidates a focused study guide for the upcoming recruitment rush.

Docker Interview Questions

What is Docker?

What is a Docker image?

What is a Docker container?

What are the possible states of a Docker container?

What is the most common instruction in a Dockerfile?

What is the difference between the COPY and ADD commands in a Dockerfile?

Common Docker commands?

Commands for copying data between host and container?

Command to start an Nginx container with random port mapping and mount a local directory to the container's HTML directory?

Explain the ONBUILD instruction in a Dockerfile.

What is Docker Swarm?

How to monitor Docker in production?

How does Docker run containers on non‑Linux systems?

How to batch clean temporary image files?

How to view environment variables supported by an image?

Where are local image files stored?

Principles to follow when building Docker images?

If a container exits and is not shown by docker ps, is its data lost?

How to stop all running containers?

How to clean up stopped containers in bulk?

How to detach from an interactive container without terminating it?

How to view output and logs of background containers?

What does the error "No public port '80' published for ..." mean when using docker port?

Can multiple applications run in a single container?

How to control a container's CPU and memory share?

Relationship between Repository, Registry, and Index?

Where are Docker configuration files located and how to modify them?

How to change Docker's default storage settings?

Differences between Docker and Vagrant?

Differences between Docker and LXC (Linux Containers)?

Nginx Interview Questions

Explain what Nginx is.

List some features of Nginx.

Differences between Nginx and Apache.

How does Nginx handle HTTP requests?

How to block requests using an undefined server name?

Advantages of using a reverse proxy server.

Best use cases for an Nginx server.

Explain the roles of Master and Worker processes in Nginx.

How to start Nginx on a non‑standard port.

Can Nginx error responses be replaced with 502/503 errors?

How to preserve double slashes in a URL.

Purpose of the ngx_http_upstream_module.

What is the C10K problem?

Functions of the stub_status and sub_filter directives.

Does Nginx support compressing requests to upstream servers?

How to obtain the current time in Nginx.

Purpose of the -s flag in Nginx commands.

How to add modules to Nginx.

Why use Nginx?

Reasons for Nginx's high performance.

How does Nginx process requests?

Difference between forward and reverse proxy.

Advantages of reverse proxy servers (duplicate entry).

Pros and cons of Nginx.

Typical application scenarios for Nginx.

Directory structure of Nginx.

Key sections and modules in nginx.conf.

Handling of static resources.

How Nginx solves front‑end cross‑origin issues.

Configuration of virtual hosts in Nginx.

Shell Script Interview Questions

What is a shell script and is it essential?

What is the default login shell and how to change a user's login shell?

What variable types can be used in shell scripts?

How to redirect both standard output and error output to the same location?

How to nest if statements in a shell script?

Purpose of the $? variable.

How to compare two numbers in a shell script?

Function of the break command.

Function of the continue command.

Syntax of the case statement.

Syntax of the while loop.

How to make a script executable?

Purpose of the #!/bin/bash shebang.

Syntax of the for loop.

How to debug a shell script?

How to compare strings in a shell script?

Special variables in Bourne shell (bash).

How to test for file existence?

How to write comments in a shell script?

How to read input from the terminal?

How to unset a variable or its value?

How to perform arithmetic operations?

Basic format of a do‑while loop.

How to define a function in a shell script?

How to generate a random string or number?

How to define a function that outputs colored text?

How to batch create users?

How to check if a package is installed?

How to check the status of a service?

How to verify host reachability?

Jenkins Interview Questions

What is Jenkins?

Why use Jenkins?

What is CI/CD?

Common CI tools.

What is a Jenkins pipeline?

Why use pipelines in Jenkins?

What is a Jenkinsfile and why use it?

What is Blue Ocean?

How to backup and copy files in Jenkins?

Advantages of Jenkins.

Two main components integrated by Jenkins.

Useful Jenkins plugins.

Which plugins have you used?

How to backup and restore Jenkins?

What are Maven and Jenkins?

Difference between Hudson and Jenkins.

What is continuous integration in Jenkins?

Why combine Jenkins with Selenium?

What is a CICD pipeline?

What is a build pipeline in Jenkins?

What is a Jenkins Pipeline?

What is DSL Jenkins?

What are continuous integration and deployment?

Tools for configuration management.

Differences among Maven, Ant, and Jenkins.

Which SCM tools does Jenkins support?

How to schedule builds in Jenkins?

Why use pipelines in Jenkins?

What is a Jenkinsfile?

How to create a multibranch pipeline?

These questions are intended as a quick reference; candidates can dive deeper into each topic as needed.