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container.training/slides/containers/Publishing_To_Docker_Hub.md
2020-01-14 15:43:00 -06:00

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# Publishing images to the Docker Hub
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:
```bash
docker login
```
.warning[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):
```bash
docker tag figlet jpetazzo/figlet
```
* And push it to the Hub:
```bash
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
---
class: extra-details
## 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/) and sign-in. Select "Repositories" in the blue navigation menu.
* Select "Create" in the top-right bar, and select "Create Repository+".
* Connect your Docker Hub account to your GitHub account.
* Click "Create" button.
* Then go to "Builds" folder.
* Click on Github icon and select your user and the repository that we just forked.
* In "Build rules" block near page bottom, put `/www` in "Build Context" column (or whichever directory the Dockerfile is in).
* Click "Save and Build" to build the repository immediately (without waiting for a git push).
* Subsequent builds will happen automatically, thanks to GitHub hooks.
---
## Building on the fly
- Some services can build images on the fly from a repository
- Example: [ctr.run](https://ctr.run/)
.exercise[
- Use ctr.run to automatically build a container image and run it:
```bash
docker run ctr.run/github.com/undefinedlabs/hello-world
```
]
There might be a long pause before the first layer is pulled,
because the API behind `docker pull` doesn't allow to stream build logs, and there is no feedback during the build.
It is possible to view the build logs by setting up an account on [ctr.run](https://ctr.run/).