[Cloud] 5. Docker Registry

In this post, we will learn about Docker's image Registry. Docker registry provides a function as a repository to store images created through Docker. ​ There are three types of registry supported by Docker as follows.

- A Docker Hub site that is publicly operated on the Internet

- When used inside the corporate network

- Private Local Registry that can be installed and used on your local server

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The reason for using this Docker Registry is that you can control the location of the images that are created first, and configure tools and pipelines that support CI (Continuous Integration) and CD (Continuous deployment) to enable automation of operations.

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First of all, you can use the following command to view the registry setting information of Docker on your local computer.

- command

docker info

root@test-VirtualBox:~# docker info Client: Context: default Debug Mode: false ​ Server: Containers: 1 Running: 0 Paused: 0 Stopped: 1 Images: 4 Server Version: 20.10.12 Storage Driver: overlay2 Backing Filesystem: extfs Supports d_type: true Native Overlay Diff: true userxattr: false Logging Driver: json-file Cgroup Driver: cgroupfs Cgroup Version: 1 Plugins: Volume: local Network: bridge host ipvlan macvlan null overlay Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog Swarm: inactive Runtimes: io.containerd.runc.v2 io.containerd.runtime.v1.linux runc Default Runtime: runc Init Binary: docker-init containerd version: runc version: init version: Security Options: apparmor seccomp Profile: default Kernel Version: 5.15.0-41-generic Operating System: Ubuntu 20.04.4 LTS OSType: linux Architecture: x86_64 CPUs: 1 Total Memory: 3.834GiB Name: test-VirtualBox ID: WLRT:FIRY:GPWN:2DSM:ZWM5:42WQ:BQOU:WRXC:QYAW:7X5J:WHGY:DDDM Docker Root Dir: /var/lib/docker Debug Mode: false Registry: https://index.docker.io/v1/ ==>Currently set up as a docker site on your local machine as a public registry Labels: Experimental: false Insecure Registries: 127.0.0.0/8 Live Restore Enabled: false ​ root@test-VirtualBox:~# ^C

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First of all, before entering the registry exercise, the thing to remember in the above picture is when a new image is created.

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The case where a new image is created is as follows.

- When creating a new image using dockerfile

- If you tag an existing image, a new image is created.

- When executing Commit command while container is running

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Now, let's take a look at the registory-related commands.

1. Download and run registory:2.5 image from Docker Hub to configure registory on local machine

- command

docker run -d -p 5000:5000 --restart=always --name registry registry:2.5

-d runs the registry container in the background

-p sets the host computer's port to 5000 and container port to 5000.

--restart=always automatically run the registry container when running Docker Daemon

--name registry registry:2.5 is the container Image uses registry:2.5

the container name is registry

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root@test-VirtualBox:~# docker run -d -p 5000:5000 --restart=always --name registry registry:2.5 Unable to find image 'registry:2.5' locally 2.5: Pulling from library/registry c1e54eec4b57: Pull complete 606cf3574ddf: Pull complete 9776f61d75c4: Pull complete 602df3b64569: Pull complete 0cb17236f8e2: Pull complete Digest: sha256:1a741bd1ad954fe4d7109cfdeabdf65f72c9b51b198f41f67ca1f86582bbbca8 Status: Downloaded newer image for registry:2.5 169120cef0ca68302e8a3803c1864c3d11b98954d8089ba0aba3a984c2dd4f65 ​ root@test-VirtualBox:~# docker ps -a CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 169120cef0ca registry:2.5 "/entrypoint.sh /etc…" 18 minutes ago Up 18 minutes 0.0.0.0:5000->5000/tcp, :::5000->5000/tcp registry root@test-VirtualBox:~#

As you can see from the log, the container named registry is now running. 2. Now, for testing, download ubuntu 16.04 image from docker. - docker pull ubuntu:16.04 ==> download ubuntu:16.04 from docker

root@test-VirtualBox:~# docker pull ubuntu:16.04 16.04: Pulling from library/ubuntu 58690f9b18fc: Pull complete b51569e7c507: Pull complete da8ef40b9eca: Pull complete fb15d46c38dc: Pull complete Digest: sha256:20858ebbc96215d6c3c574f781133ebffdc7c18d98af4f294cc4c04871a6fe61 Status: Downloaded newer image for ubuntu:16.04 docker.io/library/ubuntu:16.04 root@test-VirtualBox:~#

3. Create a new image using the tag command for the downloaded ubuntu image

- docker tag ubuntu:16.04 localhost:5000/my-ubuntu:1.0

==> tagging ubuntu:16.04 as localhost:5000/my-ubuntu:1.0

root@test-VirtualBox:~# docker tag ubuntu:16.04 localhost:5000/my-ubuntu:1.0 root@test-VirtualBox:~# root@test-VirtualBox:~# root@test-VirtualBox:~# docker images REPOSITORY TAG IMAGE ID CREATED SIZE ubuntu 16.04 b6f507652425 10 months ago 135MB localhost:5000/my-ubuntu 1.0 b6f507652425 10 months ago 135MB registry 2.5 bae2e2e45eb1 3 years ago 37.8MB root@test-VirtualBox:~#

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4. Save the created image as a local registry.

- docker push localhost:5000/my-ubuntu:1.0

==> copy localhost:5000/my-ubuntu:1.0 image to local registory

root@test-VirtualBox:~# docker push localhost:5000/my-ubuntu:1.0 The push refers to repository [localhost:5000/my-ubuntu] 1251204ef8fc: Pushed 47ef83afae74: Pushed df54c846128d: Pushed be96a3f634de: Pushed 1.0: digest: sha256:a3785f78ab8547ae2710c89e627783cfa7ee7824d3468cae6835c9f4eae23ff7 size: 1150

5. Now, let's delete the created image.

- # docker rmi -f localhost:5000/my-ubuntu:1.0 ==> Delete the image created with tag

root@test-VirtualBox:~# docker rmi -f localhost:5000/my-ubuntu:1.0 Untagged: localhost:5000/my-ubuntu:1.0 Untagged: localhost:5000/my-ubuntu@sha256:a3785f78ab8547ae2710c89e627783cfa7ee7824d3468cae6835c9f4eae23ff7 root@test-VirtualBox:~# docker images REPOSITORY TAG IMAGE ID CREATED SIZE ubuntu 16.04 b6f507652425 10 months ago 135MB registry 2.5 bae2e2e45eb1 3 years ago 37.8MB

6. Now, let's copy the image saved in the local registry in step 4.

- docker pull localhost:5000/my-ubuntu:1.0 ==> copy my-ubuntu:1.0 image from local registry

root@test-VirtualBox:~# docker pull localhost:5000/my-ubuntu:1.0 1.0: Pulling from my-ubuntu Digest: sha256:a3785f78ab8547ae2710c89e627783cfa7ee7824d3468cae6835c9f4eae23ff7 Status: Downloaded newer image for localhost:5000/my-ubuntu:1.0 localhost:5000/my-ubuntu:1.0 root@test-VirtualBox:~# root@test-VirtualBox:~# root@test-VirtualBox:~# docker images REPOSITORY TAG IMAGE ID CREATED SIZE ubuntu 16.04 b6f507652425 10 months ago 135MB localhost:5000/my-ubuntu 1.0 b6f507652425 10 months ago 135MB registry 2.5 bae2e2e45eb1 3 years ago 37.8MB

 

 
 
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