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Docker Image Downloaded from Pyrsia Decentralized Network - Verification

Here we will demonstrate how you will confirm that docker images are getting downloaded from Pyrsia network Docker registry provided you configure your Docker daemon config and image available to Pyrsia network.

Remove all local images

Script removes all docker images from local

for imgid in $(docker images -q); do
echo "removing Image ID: $imgid"
docker rmi -f $imgid
done

Setup Local Docker Registry

Run following command to have a local docker registry.

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

Pull image from Docker Hub

docker pull alpine:3.16.2

Docker pull log looks like below. Last line of the log states docker.io/library/alpine:3.16.2 which is very important. It shows from where the artifact got downloaded.

3.16.2: Pulling from library/alpine
Digest: sha256:bc41182d7ef5ffc53a40b044e725193bc10142a1243f395ee852a8d9730fc2ad
Status: Image is up to date for alpine:3.16.2
docker.io/library/alpine:3.16.2

Tag downloaded image to upload to local registry

Create a mapping from hostname docker.localhost to IP 127.0.0.1 in /etc/hosts file.

# Added manually for Docker Desktop
127.0.0.1 docker.localhost

Tag the image as docker.localhost:5000/alpine:3.16.2. This creates an additional tag for the existing image. When the first part of the tag is a hostname and port, Docker interprets this as the location of a registry, when pushing.

docker tag alpine:3.16.2 docker.localhost:5000/alpine:3.16.2

Now list all the images docker images and in the list includes following entries

REPOSITORY                           TAG       IMAGE ID       CREATED         SIZE
registry 2 dcb3d42c1744 2 weeks ago 24.1MB
alpine 3.16.2 9c6f07244728 2 months ago 5.54MB
localhost:5000/alpine 3.16.2 9c6f07244728 2 months ago 5.54MB
docker.localhost:5000/alpine 3.16.2 9c6f07244728 2 months ago 5.54MB
docker/desktop-vpnkit-controller v2.0 8c2c38aa676e 17 months ago 21MB
docker/desktop-storage-provisioner v2.0 99f89471f470 18 months ago 41.9MB

Push image to local registry

Push to local registry using docker push docker.localhost:5000/alpine:3.16.2 Logs shows something like following

The push refers to repository [docker.localhost:5000/alpine]
994393dc58e7: Pushed
3.16.2: digest: sha256:1304f174557314a7ed9eddb4eab12fed12cb0cd9809e4c28f29af86979a3c870 size: 528

Now check file system of local registry by logging into running docker container and list the location

# ls -ltr /var/lib/registry/docker/registry/v2/repositories/
total 4
drwxr-xr-x 5 root root 4096 Oct 25 06:51 alpine

Remove image from local cache

Remove the locally-cached alpine:3.16.2 and docker.localhost:5000/alpine:3.16.2 images, so that you can test pulling the image from your registry. This does not remove the docker.localhost:5000/alpine:3.16.2 image from your registry.

docker rmi -f alpine:3.16.2
docker rmi -f docker.localhost:5000/alpine:3.16.2
docker rmi -f localhost:5000/alpine:3.16.2

Let's Start Using Local Registry

Pull from Local Registry

Pull image from local registry

docker pull docker.localhost:5000/alpine:3.16.2

Logs look like following and important things to notice is the last line. It clearly states from where the image has been pulled.

3.16.2: Pulling from alpine
213ec9aee27d: Already exists
Digest: sha256:1304f174557314a7ed9eddb4eab12fed12cb0cd9809e4c28f29af86979a3c870
Status: Downloaded newer image for docker.localhost:5000/alpine:3.16.2
docker.localhost:5000/alpine:3.16.2

API verification from Local Registry

Verify v2 version support curl -i -X GET http://docker.localhost:5000/v2/.

Pulling an Image Manifest curl -i -X GET http://docker.localhost:5000/v2/alpine/manifests/3.16.2

Change the mirror registry to use Local Registry

Add following key:value pair to Docker daemon configuration file.

  • "insecure-registries": ["http://docker.localhost:5000"]
  • "registry-mirrors": ["http://docker.localhost:5000"]

Test Docker Pull without specifying registry host:port explicitly

Remove all the images from cache. Follow Remove image from local cache

Pull an image available in local registryPull an image not available in local registry
docker pull alpine:3.16.2docker pull alpine:3.15.6
Logs
3.16.2: Pulling from library/alpine
213ec9aee27d: Already exists
Digest: sha256:bc41182d7ef5ffc53a40b044e725193bc10142a1243f395ee852a8d9730fc2ad
Status: Downloaded newer image for alpine:3.16.2
docker.io/library/alpine:3.16.2
Logs
3.15.6: Pulling from library/alpine
9621f1afde84: Pull complete
Digest: sha256:69463fdff1f025c908939e86d4714b4d5518776954ca627cbeff4c74bcea5b22
Status: Downloaded newer image for alpine:3.15.6
docker.io/library/alpine:3.15.6
When it already in local registry, in the log it shows Already existsWhile it is not in local registry, it shows Pull complete

Therefore, in docker pull <image> log says Already exists, it means that it is getting pulled from one of the mirror. Configuring mirrors doesn't ensure that you are always pulling from internal mirror. Docker checks at the mirror first and then falls back to DockerHub registry.

sequenceDiagram participant Docker Client participant Docker Daemon Config participant Docker Local Registry participant Docker Hub Docker Client->>Docker Client: docker pull alpine:3.16.2 Docker Client->>+Docker Daemon Config: Get Registry Mirros Docker Daemon Config-->>-Docker Client: Array of Mirros Docker Client->+Docker Local Registry: try to pull alpine:3.16.2 from mirros Docker Local Registry->>Docker Local Registry: Find alpine:3.16.2 Docker Local Registry-->>-Docker Client: Awesome! Found in local registry. Note right of Docker Local Registry: 213ec9aee27d: Already exists Docker Client->>Docker Client: docker pull alpine:3.15.6 Docker Client->>+Docker Daemon Config: Get Registry Mirros Docker Daemon Config-->>-Docker Client: Array of Mirros Docker Client->+Docker Local Registry: try to pull alpine:3.15.6 from mirros Docker Local Registry->>Docker Local Registry: Find alpine:3.15.6 Docker Local Registry-->>-Docker Client: Didn't find in local registry. Docker Client->>+Docker Hub: try to pull alpine:3.15.6 from Docker Hub Docker Hub->>Docker Hub: Find alpine:3.15.6 Docker Hub-->>-Docker Client: Awesome! Found in Docker Hub. Note right of Docker Hub: 9621f1afde84: Pull complete

Set Pyrsia Decentralize Network as Docker Registry Mirror

Set Pyrsia Decentralize Network as Docker Registry Mirror in the same way we did it local Docker Registry

Get Pyrsia Node cofig

Use pyrsia config --show to get your node config details. Assume your node details are like below.

host = '0.0.0.0'
port = '7888'
disk_allocated = '10 GB'

Change Docker daemon config

Create a following key:value pair for Docker daemon config and append to the existing config

  • "insecure-registries": ["http://0.0.0.0:7888"]
  • "registry-mirrors": ["http://0.0.0.0:7888"]

Apply the config & restart Docker daemon process. Wait for Docker to daemon to restart cleanly.

Pull Image from Pyrsia

Try to get inspect log from Pyrsia using pyrsia inspect-log docker --image alpine:3.16.2. If you find the entries in inpect log it means the image is available in Pyrsia. Now remove all the images from local cache. Follow Remove image from local cache.

Try to pull the image docker pull alpine:3.16.2. You should able to see something like

3.16.2: Pulling from library/alpine
213ec9aee27d: Already exists
Digest: sha256:bc41182d7ef5ffc53a40b044e725193bc10142a1243f395ee852a8d9730fc2ad
Status: Downloaded newer image for alpine:3.16.2
docker.io/library/alpine:3.16.2

In the log we can see Already exists text and this indicates that docker client found it in the mirrors (i.e. Pyrsia network) and pulled it from Pyrsia docker registry.