Essential Docker CLI Commands for Beginners (With Examples and Explanation)

The Docker Command Line Interface (CLI) is the main way developers interact with Docker. If you understand Docker CLI commands, you can easily create, run, and manage containers.

This guide explains Docker commands in a simple and practical way with real examples and syntax explanations so beginners can understand easily. :contentReference[oaicite:0]{index=0}

Related internal topics: /docker-installation, /docker-images-containers, /dockerfile-tutorial, /docker-architecture.

1. How Docker Works (Simple Flow)

Before learning commands, understand the workflow:

[ Docker Hub / Registry ]
        |
        | (download image)
        v
[ Local Machine (Images) ]
        |
        | (run command)
        v
[ Running Container ]
        |
        | (stop/remove)
        v
[ Stopped Container ]

In simple words:

• You download an image
• You run it as a container
• You stop or delete it when done

2. System Information Commands

Command 1: Check Docker Version

docker version

Explanation: Shows Docker client and server versions.

Command 2: Check Docker Details

docker info

Explanation: Displays system details like number of containers, images, memory usage.

Example

If Docker is not running, this command will fail. So it helps verify installation.

3. Working with Docker Images

Images are like templates (similar to Java class). Containers are instances (like objects).

Command: Pull Image

docker pull nginx

Explanation:

• Downloads nginx image from Docker Hub
• Stores it locally

Command: List Images

docker images

Explanation: Shows all downloaded images.

Command: Remove Image

docker rmi nginx

Explanation: Deletes an image.

Example

If you no longer need nginx:

docker rmi nginx

This frees disk space.

4. Working with Containers

Command: Run Container

docker run --name my-nginx -d -p 8080:80 nginx

Explanation:

• docker run → Creates and starts container
• --name my-nginx → Custom container name
• -d → Run in background
• -p 8080:80 → Map port 8080 (host) to 80 (container)
• nginx → Image name

Real Example

After running the above command:

• Open browser
• Go to http://localhost:8080
• You will see nginx welcome page

Command: List Running Containers

docker ps

Explanation: Shows currently running containers.

Command: List All Containers

docker ps -a

Explanation: Shows running + stopped containers.

Command: View Logs

docker logs my-nginx

Explanation: Shows output logs of container.

Command: Stop Container

docker stop my-nginx

Explanation: Gracefully stops container.

Command: Remove Container

docker rm my-nginx

Explanation: Deletes container permanently.

5. Useful Advanced Commands

Run Command Inside Container

docker exec -it my-nginx /bin/bash

Explanation:

• Access container terminal
• -it → interactive mode

Check Resource Usage

docker stats

Explanation: Shows CPU, memory usage of containers.

Clean Unused Resources

docker system prune

Explanation: Removes unused containers, images, cache.

6. Real-World Use Case (Java Developer)

Instead of installing Java manually, you can use Docker:

docker run -it --rm openjdk:17 java -version

Explanation:

• -it → interactive terminal
• --rm → auto delete container after run
• openjdk:17 → Java image

This is useful for testing Java versions without installing them.

7. Flow Chart: Container Lifecycle

Create Container (docker run)
        |
        v
Running State
        |
        v
Stopped State (docker stop)
        |
        v
Deleted (docker rm)

8. Common Mistakes to Avoid

1. Not Cleaning Containers

Too many unused containers consume disk space.

2. Confusing Image and Container

Image = template, Container = running instance.

3. Port Conflicts

Running multiple containers on same port causes error.

4. Not Using Names

Without names, managing containers becomes difficult.

5. Forgetting Detached Mode

Without -d, terminal gets blocked.

9. Interview Notes

Difference between docker stop and docker kill?

docker stop → Graceful shutdown

docker kill → Force stop immediately

How to access running container?

docker exec -it container_name /bin/bash

How to check container logs?

docker logs container_name

How to check running containers?

docker ps

What is docker run?

Creates and starts a container from image.

10. Summary

Docker CLI is the main tool to manage containers. By learning basic commands like docker pull, docker run, docker ps, and docker stop, you can control the entire container lifecycle.

With Docker CLI, developers can quickly create environments, test applications, and deploy services efficiently. It simplifies development and is widely used in modern DevOps and microservices architecture.

Next step: Learn /docker-images-containers to understand how images and containers work internally.