Docker 101 : Docker Registry

The docker registry is a program that you can also run on your machine.
Its role is storing docker images and their metadata ( tags, ... ).

The docker registry is also a service that opens port 5000 for incoming queries, like pushing, pulling or loading a docker image.
It can also authenticates users.

Running a registry service:

We run the registry image using the below command:

-p : for publishing the ports,  it  maps port 5000 of the host to port 5000 on the container.
-d : for the detached mode. The container will run in the background.
--restart: when it is set to "always", the container is restarted 
if it crashes.

Pushing an image to our registry:

We first tag our "debian" image:

Then we push it onto the registry on our localhost:

Saving images locally:

To save our image locally, we use the below command:

-o: tells docker to save the image "debian:12" into the "saved-images.tar.gz" file.

The saved images could also be easily moved to a different machine or to a different cluster.

Removing and restoring our image:

We can remove our image "debian:12" using the below command:

Then we could restore it using the "load" command as below:

-i: stands for the input file from which we load our image.


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