Image

Important concepts

1. Image layers

   Docker doesn't store entire image in a bundle. It stores each layer of an image, only once.

2. union file system

   A same image layer can be shared in different images.

3. container

   A container just a single read/write layer on the top of image. It's usually very small.

Get an image

docker pull <image>

Name

Image doesn't have name. To identify an image, we use:

<user>/<repo>:<tag>

An Image can have multiple tags.

Build an image

Dockerfile is an instruction of building an image.

docker image build -t <name> PATH

If PATH is ., it means we build image based on the Dockerfile in the current repo.