Docker images are the foundation of containers. They are lightweight, standalone, and executable software packages that include everything needed to run a piece of software, including the code, runtime, libraries, environment variables, and configuration files.

1. Docker Image: A read-only template with instructions for creating a Docker container. Often, an image is based on another image, with some additional customization.
2. Layers: Docker images are built in layers. Each layer represents an instruction in the image’s Dockerfile. Layers are stacked on top of each other to form the final image.
3. Union File System: Docker uses a union file system to combine these layers into a single image.
4. Base Image: The starting point for creating a Docker image. It can be a minimal OS image or a more complex image with pre-installed software.
5. Image ID: A unique identifier for each image.
6. Tags: Labels that point to specific versions of images. The default tag is latest.

Docker Hub is a public repository where Docker images are stored. You can pull images from Docker Hub using the docker pull command.

Explanation:

• docker pull: Command to download an image from a repository.
• ubuntu: The name of the image.
• latest: The tag specifying the version of the image.

You can inspect an image to see its details using the docker inspect command.

This command will output detailed information about the image, including its layers, configuration, and more.

To see all the images you have on your system, use the docker images command.

This will display a table with the repository name, tag, image ID, creation date, and size of each image.

If you no longer need an image, you can remove it using the docker rmi command.

1. Pull the nginx image from Docker Hub.
2. List all images on your system.
3. Inspect the nginx image to see its details.
4. Remove the nginx image from your system.

1. Pull the nginx image:

   docker pull nginx:latest
   

2. List all images:

   docker images
   

3. Inspect the nginx image:

   docker inspect nginx:latest
   

4. Remove the nginx image:

   docker rmi nginx:latest
   

• Forgetting to Tag: When pulling or building images, always specify a tag to avoid confusion.
• Unused Images: Regularly clean up unused images to save disk space using docker image prune.
• Image Size: Be mindful of image size. Smaller images are faster to pull and use less disk space.

Understanding Docker images is crucial for working effectively with Docker. Images are the building blocks of containers, and knowing how to manage them will help you create efficient and reliable containerized applications. In the next topic, we will dive deeper into creating your first Docker container using these images.