Configure local container registry for Docker
Configuring a local container registry can be useful if we are building our images and need fast access to them, it might also be useful when having a local Kubernetes cluster for example. In this post we will see how to setup a local container registry, how to pull images from one registry and push them to our own registry and how to push images that we built ourselves to the registry.
Installing Docker on Linux
First things first we will need Docker installed. If you already have it you can move onto the next section, otherwise here is a quick command reference to install Docker on Ubuntu 22.04:
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sudo apt install apt-transport-https ca-certificates curl software-properties-common
sudo curl -fsSL https://download.docker.com/linux/ubuntu/gpg | gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg
sudo echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable" | tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt update
sudo apt-cache policy docker-ce
sudo apt install docker-ce
Finally, we can check if Docker is running by executing sudo systemctl status docker on our system.
Install local container registry
Now comes the important part, installing the local container registry. To do so, run the following command:
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docker run -d -p 5000:5000 --restart always --name registry registry:2
We should give a hostname to the computer where we are running our container registry. I will assume from now on that we named it container-registry.local, if you do not have a local DNS to set this up, remember to configure the hosts file of all the computers where you need to access this container registry to point container-registry.local to the IP of the container registry (included the hosts file of the computer where our container registry is installed).
Moving images from a remote container registry to our own
Moving images from a remote container registry to the one we installed locally is a three command operation: first pull the image, then tag it and finally push it.
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docker pull nginx:1.24
docker tag nginx:1.24 container-registry.local:5000/nginx:1.24
docker push container-registry.local:5000/nginx:1.24
Now the image should be available on our container registry.
Push built image to local container registry
If we want to push an image we built using Dockerfile to our container registry, you have to build the image while assigning it the correct tag, then push it.
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docker build . --tag=container-registry.local:5000/myimage:1.0.0
docker push container-registry.local:5000/myimage:1.0.0
Of course we could have used a subpath if we wanted, to organize it better. In that case, we have to replace container-registry.local:5000/myimage:1.0.0 with container-registry.local:5000/path/to/myimage:1.0.0. We can have as many subpaths as we want. Also remember to replace the version tag with the correct value for your application.
List all container registry images
We can check how many images we have on our container registry at any time by running the following command:
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curl -X GET http://container-registry.local:5000/v2/_catalog
We can also list all the tags for a given image:
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curl -X GET http://container-registry.local:5000/v2/myimage/tags/list
Replace myimage with the correct image name, also include the full path if necessary (for example http://container-registry.local:5000/v2/path/to/myimage/tags/list).