Docker

Images

Docker images are the basis of containers. An Image is an ordered collection of root filesystem changes and the corresponding execution parameters for use within a container runtime. An image typically contains a union of layered filesystems stacked on top of each other. An image does not have state and it never changes.

Containers

A Docker container is a runtime instance of a docker image.

A Docker container consists of:

  • A Docker image
  • An execution environment
  • A standard set of instructions

The concept is borrowed from Shipping Containers, which define a standard to ship goods globally. Docker defines a standard to ship software.

Docker Containers vs. Virtual Machines