Docker is a command that can build, fetch, and run docker images from a docker registry and orchestrates running those typically on a linux host or virtual machine.
A docker image is a set of hashes that identify layers in a layered filesystem. A docker registry stores those layers and the docker looks up layers from the registry. The combined layers form a filesystem that is mounted when you run the docker image. A running docker image is called a docker container.
To create a docker image with docker, you use a Dockerfile that specifies a sequence of steps that modify the layered file system, typically starting from a base image that is specified in the first line.
The company Docker Inc. is a major contributor to the open source docker code base and also owns and runs a popular docker registry called Docker Hub, which is what the docker command uses as default place to look for docker images.
While docker is popular, there are alternative tools that are able to run docker images. For example Kubernetes implements its own way to run docker images. Likewise, there are build tools that produce docker images without using the docker command or a Dockerfile. And the docker registry API is simple enough that you don't need docker to fetch layers either.
Consequently, there are several popular tools in this space. That do similar things with varying degrees of compatibility. Many of these can run docker containers from Docker Hub.
Docker is a command that can build, fetch, and run docker images from a docker registry and orchestrates running those typically on a linux host or virtual machine.
A docker image is a set of hashes that identify layers in a layered filesystem. A docker registry stores those layers and the docker looks up layers from the registry. The combined layers form a filesystem that is mounted when you run the docker image. A running docker image is called a docker container.
To create a docker image with docker, you use a Dockerfile that specifies a sequence of steps that modify the layered file system, typically starting from a base image that is specified in the first line.
The company Docker Inc. is a major contributor to the open source docker code base and also owns and runs a popular docker registry called Docker Hub, which is what the docker command uses as default place to look for docker images.
While docker is popular, there are alternative tools that are able to run docker images. For example Kubernetes implements its own way to run docker images. Likewise, there are build tools that produce docker images without using the docker command or a Dockerfile. And the docker registry API is simple enough that you don't need docker to fetch layers either.
Consequently, there are several popular tools in this space. That do similar things with varying degrees of compatibility. Many of these can run docker containers from Docker Hub.