We've already discussed Docker Hub. It is the biggest and most popular Docker repository available on the web. It is available at https://hub.docker.com. The Docker client, by default, tries to pull all the images for that repository. There are many certified official images for common software such as Redis, Java, Nginx, or Mongo, but you may also find hundreds of thousands of images created by other people as well. If you use the command docker run , the image is pulled from the repository in case it is not cached locally. You may also run the following command docker pull, which is only responsible for downloading an image:
$ docker pull postgres
The preceding command downloads the newest version of an image ...
