What are Image Registries

A registry is a repository used to store and access container images. Container registries can support container-based application development, often as part of DevOps processes.

Container registries save developers valuable time in the creation and delivery of cloud-native applications, acting as the intermediary for sharing container images between systems. They essentially act as a place for developers to store container images and share them out via a process of uploading (pushing) to the registry and downloading (pulling) into another system, like a Kubernetes cluster.

Some examples of an image registry are Red Hat Quay and IBM Cloud Registry.

Learn More

Quay Tutorial

PodmanDocker

Make sure you have Podman Desktop installed and up and running.

Here's how to find a list of publicly available container images on DockerHub.

Find Container Image

podman search docker.io/busybox

Output:

NAME                                         DESCRIPTION
docker.io/library/busybox                    Busybox base image.
docker.io/rancher/busybox
docker.io/openebs/busybox-client
docker.io/antrea/busybox
docker.io/hugegraph/busybox                  test image
...

We can create a busybox container image based off of the busybox base image you see listed in the output above.

Create Image

podman run -it docker.io/library/busybox

The -it flag allows you to run the image in interactive mode. Interactive mode in Podman allows you to run a shell in a container and interact with it. However, you'll see that running small containers like this one don't have much to play around with in the interactive mode. To exit out of the interactive mode:

Exit Interactive mode

exit

You can also share images in a public registry so that others can use and review them. Here's how to push your image up to quay.io.

Login to quay.io

podman login quay.io

Enter in the following info:

Username: your_username
Password: your_password

Next, tag the image so that you can push it and find it in your account.

Tag Image

podman tag <image_name> quay.io/your_username/image_registry_name

Make sure to replace "image_name" with the name of the image you want to push up to quay. Replace "user_name" with your quay.io username. Replace "image_registry_name" with what you want the image to be named/labeled as in quay.

Once the image is tagged, you can push it up to quay.

Push Image

podman push quay.io/your_username/image_registry_name

Your respository has now been pushed to Quay Container Registry!

To view your repository, click on the button below:

Repositories

Make sure you have Docker Desktop installed and up and running.

Login to Quay

docker login quay.io
Username: your_username
Password: your_password
Email: your_email

First we'll create a container with a single new file based off of the busybox base image:

Create a new container

docker run busybox echo "fun" > newfile

The container will immediately terminate, so we'll use the command below to list it:

docker ps -l

The next step is to commit the container to an image and then tag that image with a relevant name so it can be saved to a respository.

Replace "container_id" with your container id from the previous command.

Create a new image

docker commit container_id quay.io/your_username/repository_name

Be sure to replace "your_username" with your quay.io username and "respository_name" with a unique name for your repository.

Now that we've tagged our image with a repository name, we can push the respository to Quay Container Registry:

Push the image to Quay

docker push quay.io/your_username/repository_name

Your respository has now been pushed to Quay Container Registry!

To view your repository, click on the button below:

Repositories

IBM Cloud Registry Tutorial

PodmanDocker

1. Install the Container Registry CLI

Before you begin, you need to install the IBM Cloud CLI so that you can run the IBM Cloud ibmcloud commands.

Install the container-registry CLI

ibmcloud plugin install container-registry

2. Set up a namespace

Then, you need to create a namespace. The namespace is created in the resource group that you specify so that you can configure access to resources within the namespace at the resource group level. If you don't specify a resource group, then the default is used.

Log in to IBM Cloud

ibmcloud login

Create namespace

ibmcloud cr namespace-add <my_namespace>

Make sure to replace <my_namespace> with your preferred namespace.

If you want to create the namespace in a specific resource group, use the following code before creating the namespace.

Specify a resource group

ibmcloud target -g <resource_group>

Replace <resource_group> with the resource group you want to create the namespace in.

To validate the namespace was created, run the following command.

Validate namespace is created

ibmcloud cr namespace-list -v

3. Pull images from a registry to your local computer

Next, you can pull images from IBM Cloud Registry to your local computer. Make sure Podman is installed and up and running.

Pull image to local computer

podman pull <source_image>:<tag>

Replace <source_image> with the respository of the image and <tag> with the tag of the image that you want to use.

Below is an example where <source_image> is "hello-world" and <tag> is "latest".

podman pull hello-world:latest

4. Tag the image

Tags are used as an optional identifier to specify a particular version of an image.

Tag image

podman tag <source_image>:<tag> <region>.icr.io/<my_namespace>/<new_image_repo>:<new_tag>

Replace <source_image> with the respository of the image, <tag> with the tag of your local image that you previously pulled, <region> with the name of your region, and <my_namespace> with the namespace you created in step 2. You'll want to define the repository and tag of the image that you want to use in your namespace by replacing <new_image_repo> and <new_tag> respectively.

Below is an example where <source_image> is "hello-world", <tag> is "latest", <region> is "uk", <my_namespace> is "namespace1", <new_image_repo> is "hw_repo", and <new_tag> is "1".

podman tag hello-word:latest uk.icr.io/namespace1/hw_repo:1

5. Push images to your namespace

First, you'll need to log in to IBM Cloud Container Registry.

Log in to ICR

ibmcloud cr login --client podman

Once you've logged in, you can push the image up to your namespace in the registry.

Push image to your namespace

podman push <region>.icr.io/<my_namespace>/<image_repo>:<tag>

Replace <my_namespace> with the namespace you created in step 2 and <image_repo> and <tag> with the repository and tag of the image you chose when you tagged the image in step 4.

Below is an example where <region> is "uk", <my_namespace> is "namespace1", <image_repo> is "hw_repo", and <tag> is "1".

podman push uk.icr.io/namespace1/hw_repo:1

6. Verify that the image was pushed

Verify that the image was pushed successfully by running the comand below.

ibmcloud cr image-list

You can also view your pushed images by clicking on the button below:

Images