Docker Images and Containers

One of the most important Docker concepts:

Images and containers are NOT the same thing.

Docker Image

An image is a template.

Think of it like:

• blueprint
• snapshot
• application package

Images are read-only.

Example:

docker pull nginx

This downloads an image.

Docker Container

A container is a running instance of an image.

Example:

docker run nginx

This creates and starts a container.

Visual Explanation

Docker Image
     ↓
Creates
     ↓
Docker Container

One image can create many containers.

Real Example

Pull Ubuntu image:

docker pull ubuntu

Run container:

docker run -it ubuntu bash

Breakdown:

Container Lifecycle

Containers move through states:

Created
   ↓
Running
   ↓
Stopped
   ↓
Removed

Useful commands:

docker ps
docker stop
docker start
docker rm

Important Docker Commands

List running containers:

docker ps

List all containers:

docker ps -a

List images:

docker images

Remove container:

docker rm CONTAINER_ID

Remove image:

docker rmi IMAGE_ID