How to Install Docker on Rocky Linux 9

Introduction

Docker is an open-source platform that enables the creation, packaging, distribution and deployment of applications using lightweight portable containers. A container includes the runtime dependencies, libraries, code, and configuration parameters required for an application to run in multiple environments on any host.

This article explains how to install Docker on a Rocky Linux 9 and run containerized applications on your server.

Prerequisites

Before you begin:

• Deploy a Rocky Linux 9 instance on Vultr.
• Create a Vultr Container Registry to store your Docker images.
• Access your server using SSH as a non-root user with sudo privileges
• Update the server.

Install Docker

Docker is available in the default package repositories on Rocky Linux 9, but the version information may not be the latest. Follow the steps below add the latest repository information and install Docker on your server using the default DNF package manager.

1. Install the dnf-utils package.

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   $ sudo dnf install -y dnf-utils
   

2. Add the official Docker repository to your package sources.

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   $ sudo dnf config-manager --add-repo https://download.docker.com/linux/rhel/docker-ce.repo
   

3. Install Docker and all required dependency packages such as containerd.io.

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   $ sudo yum install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
   

Manage the Docker System Service

The Docker engine uses the docker systemd service to run and manage the daemon processes on your server. Only privileged users can access Docker CLI and manage the containerized application processes. Follow the steps below to manage the Docker system service and enable unprivileged system users to use Docker CLI to manage containerized applications on the server.

1. Enable the Docker service to automatically start at system boot.

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   $ sudo systemctl start docker
   

2. Start the Docker service.

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   $ sudo systemctl start docker
   

3. View the Docker service status and verify that it's running.

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   $ sudo systemctl status docker
   

   Output:

   ● docker.service - Docker Application Container Engine
        Loaded: loaded (/usr/lib/systemd/system/docker.service; disabled; preset: disabled)
        Active: active (running) since Sat 2024-07-06 00:00:46 UTC; 35s ago
   TriggeredBy: ● docker.socket
          Docs: https://docs.docker.com
      Main PID: 6412 (dockerd)
         Tasks: 7
        Memory: 65.5M
           CPU: 233ms
        CGroup: /system.slice/docker.service
                └─6412 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock

   The Docker service is active and running on your server based on the active (running) prompt in the above output.

4. Stop the Docker service.

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   $ sudo systemctl stop docker
   

5. Restart the Docker service.

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   $ sudo systemctl restart docker
   

Deploy Containerized Applications using Docker

Docker can find and run applications from container image sources such as Docker Hub. Follow the steps below to deploy a sample containerized application using the hello world image from Docker Hub and verify the container processes on your server.

1. Pull the crccheck/hello-world Docker image from Docker Hub.

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   $ docker pull crccheck/hello-world
   

2. List all Docker images available on your server and verify that the new image is available.

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   $ docker images
   

   Output:

   REPOSITORY             TAG       IMAGE ID       CREATED       SIZE
   crccheck/hello-world   latest    24349d78cb62   2 years ago   1.24MB

3. Deploy a new containerized application using the hello-world Docker image.

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   $ docker run -d --name web-test -p 80:8000 crccheck/hello-world
   

   The above command runs a new Docker container with the following configuration:

   • -d: Starts the container in detached mode as a background process.
   • --name web-test: Assigns the containerized application name web-test for identification and management.
   • -p 80:8000: Maps the localhost port 80 to the container port 8000 to enable access the containerized application.
   • crccheck/hello-world: Sets the Docker image to use when creating the container

4. List all active Docker containers running on your server.

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   $ docker ps
   

   Verify that the web-test container is active running similar to the following output.

   CONTAINER ID   IMAGE                  COMMAND                   CREATED         STATUS                            PORTS                                   NAMES
   74609506c374   crccheck/hello-world   "/bin/sh -c 'echo \"h…"   6 seconds ago   Up 6 seconds (health: starting)   0.0.0.0:80->8000/tcp, :::80->8000/tcp   web-test

5. Access your localhost port 80 using the curl utility and verify that your application responds to user requests.

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   $ curl 127.0.0.1:80
   

   Output:

   Hello World

6. Access your server IP address using a web browser such as Chrome and verify that your application's graphical interface page displays.

   http://SERVER-IP:80

   Output:

   

7. Run the following command to stop the Docker container.

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   $ docker stop web-test
   

Log in to a Container Registry

Docker supports private and public container registries such as the Vultr container registry to build, store and deploy container images. Follow the steps below to use Docker with your Vultr Container Registry to deploy containerized applications on the server.

1. Access your Vultr Container Registry's management page and copy the docker login command in the Example Commands section that contains all necessary credentials.

   

2. Run the docker login in your terminal session to log in to the Vultr Container Registry. Replace exampleregistry, example-user, and registry-key with your actual details.

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   $ docker login https://sjc.vultrcr.com/exampleregistry -u example-user -p registry-key
   

   Your output should be similar to the one below when successful:

   Login Succeeded

3. Tag the crccheck/hello-world Docker image with your desired Vultr Container Registry repository name.

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   $ docker tag crccheck/hello-world:latest sjc.vultrcr.com/exampleregistry/crccheck/hello-world:latest
   

4. List all Docker images and verify that the new tagged image is available.

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   $ docker images
   

   Output:

   REPOSITORY                                       TAG       IMAGE ID       CREATED       SIZE
   crccheck/hello-world                             latest    24349d78cb62   2 years ago   1.24MB
   sjc.vultrcr.com/exampleregistry/crccheck/hello-world   latest    24349d78cb62   2 years ago   1.24MB

5. Push the tagged Docker image to your Vultr Container Registry.

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   $ docker push sjc.vultrcr.com/exampleregistry/crccheck/hello-world:latest
   

   Your output should be similar to the one below.

   The push refers to repository [sjc.vultrcr.com/exampleregistry/crccheck/hello-world]
   e35bd73d1b9a: Pushed
   d94c78be1352: Pushed
   latest: digest: sha256:0404ca69b522f8629d7d4e9034a7afe0300b713354e8bf12ec9657581cf59400 size: 734

6. Access your Vultr Container Registry's management page, navigate to the Repositories tab and verify that the new Docker image repository is available.

   

7. Deploy a new container using your Vultr Container Registry Docker image.

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   $ docker run -d --name web-test-vcr -p 80:8000 sjc.vultrcr.com/exampleregistry/crccheck/hello-world:latest
   

8. List all active Docker containers running on your server.

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   $ docker ps
   

   Verify that the web-test-vcr container is running similar to the following output.

   CONTAINER ID   IMAGE                  COMMAND                   CREATED         STATUS                            PORTS                                   NAMES
   74609506c374   sjc.vultrcr.com/exampleregistry/crccheck/hello-world:latest   "/bin/sh -c 'echo \"h…"   6 seconds ago   Up 6 seconds (health: starting)   0.0.0.0:80->8000/tcp, :::80->8000/tcp   web-test-vcr

Conclusion

You have installed Docker on Rocky Linux 9 and deployed containerized applications on your server. Docker supports multiple container image sources you can use to run containerized applications on your server. For more information and Docker CLI options, visit the Docker reference documentation.