Docker basics: Docker Registry

By default when using docker you pull the images from the Dockerhub docker registry. Most probably you have your own docker images for you application and you want to distribute them and do so in a secure way. One way to do so is to go with the already set options such as a paid plan from Dockerhub or the registries provided by cloud providers like amazon, azure etc.

The other option is setting up your own docker registry.
In any case since you use docker you need to have a registry to distribute your images so that they can make it into production.
There are many benefits on managing your own registry but be aware that it requires effort on your side on provisioning and maintaining it.
Therefore we will create our docker registry

docker run -d -p 5000:5000 --restart=always --name registry registry:2

So we have a docker registry running on port 5000 and the registry will always restart.

Now let’s test our registry and push an image.
First I will build a simple image with no specific purpose.

FROM ubuntu
ENTRYPOINT top

It is just a dummy image printing top.

so we are gonna build it

docker build --tag top-ubuntu:1.0 .

The key is to tag your image based on the domain under which your registry runs.
Currently our registry runs on the localhost therefore by tagging we also specify the location of the registry.

docker tag top-ubuntu:1.0 localhost:5000/top-ubuntu:1.0

And no we push our image

docker push localhost:5000/top-ubuntu:1.0

Now let’s remove our images and see if our image will be downloaded from our running registry

docker rmi top-ubuntu:1.0
docker rmi localhost:5000/top-ubuntu:1.0

And let’s pull

docker pull localhost:5000/top-ubuntu:1.0

As you can see our image has been downloaded from our local registry and is ready to be used.

So far so good. The next step is securing our registry with a username and password.

Let’s start by setting the username and password

First let’s create a directory which shall contain our credentials

mkdir auth

The we shall creae

docker run --entrypoint htpasswd registry:2 -Bbn {your-user} {your-password} > auth/password-file

The file shall contain your username and password information. The password shall be hashed.

Now let’s run our secured registry

 docker run -d -p 5000:5000 --restart=always --name registry -v `pwd`/auth:/auth -e "REGISTRY_AUTH=htpasswd" -e "REGISTRY_AUTH_HTPASSWD_REALM=Registry Realm" -e REGISTRY_AUTH_HTPASSWD_PATH=/auth/password-file registry:2

As you can see we mounted the credentials file to the docker container and we specified the location of the password-file.

Let’s try to push our image

docker push localhost:5000/top-ubuntu:1.0
.
.
.

059ad60bcacf: Preparing 
8db5f072feec: Preparing 
67885e448177: Preparing 
ec75999a0cb1: Preparing 
65bdd50ee76a: Preparing 
no basic auth credentials

It’s time to login to our registry

docker login localhost:5000

Once your have provided your credentials you will be able to push the image to your local repository.

docker push localhost:5000/top-ubuntu:1.0

Be aware that our registry is not secure. Having your registry secured with credentials does not make it secure since you need to have ssl encryption.

On the next tutorial we will secure a docker registry with ssl.

 

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