Publishing images to the Docker Hub

Introduction

We have built our first images.

We can now publish it to the Docker Hub!

You don't have to do the exercises in this section, because they require an account on the Docker Hub, and we don't want to force anyone to create one.

Note, however, that creating an account on the Docker Hub is free (and doesn't require a credit card), and hosting public images is free as well.

Logging into our Docker Hub account

  • This can be done from the Docker CLI:
    docker login

When running Docker for Mac/Windows, or Docker on a Linux workstation, it can (and will when possible) integrate with your system's keyring to store your credentials securely. However, on most Linux servers, it will store your credentials in ~/.docker/config.

Image tags and registry addresses

  • Docker images tags are like Git tags and branches.

  • They are like bookmarks pointing at a specific image ID.

  • Tagging an image doesn't rename an image: it adds another tag.

  • When pushing an image to a registry, the registry address is in the tag.

    Example: registry.example.net:5000/image

  • What about Docker Hub images?

  • jpetazzo/clock is, in fact, index.docker.io/jpetazzo/clock

  • ubuntu is, in fact, library/ubuntu, i.e. index.docker.io/library/ubuntu

Tagging an image to push it on the Hub

  • Let's tag our figlet image (or any other to our liking):

    docker tag figlet jpetazzo/figlet

  • And push it to the Hub:

    docker push jpetazzo/figlet

  • That's it!

  • Anybody can now docker run jpetazzo/figlet anywhere.

The goodness of automated builds

  • You can link a Docker Hub repository with a GitHub or BitBucket repository

  • Each push to GitHub or BitBucket will trigger a build on Docker Hub

  • If the build succeeds, the new image is available on Docker Hub

  • You can map tags and branches between source and container images

  • If you work with public repositories, this is free

Setting up an automated build

  • We need a Dockerized repository!
  • Let's go to https://github.com/jpetazzo/trainingwheels and fork it.
  • Go to the Docker Hub (https://hub.docker.com/).
  • Select "Create" in the top-right bar, and select "Create Automated Build."
  • Connect your Docker Hub account to your GitHub account.
  • Select your user and the repository that we just forked.
  • Create.
  • Then go to "Build Settings."
  • Put /www in "Dockerfile Location" (or whichever directory the Dockerfile is in).
  • Click "Trigger" to build the repository immediately (without waiting for a git push).
  • Subsequent builds will happen automatically, thanks to GitHub hooks.