Docker*

Clear Linux* OS supports multiple containerization platforms, including a Docker solution. Clear Linux OS has many unique features including a minimal default installation, which makes it compelling to use as a host for container workloads, management, and orchestration.

This tutorial covers:

注解

This tutorial focuses on the installaton of the Docker ecosystem. If you want to use Clear Linux OS as a Docker container image, refer to the official Clear Linux OS container image published on Docker* Hub and our guide to 根据 Docker 容器映像构建一个自定义 Clear Linux* OS.

Prerequisites

This tutorial assumes you have installed Clear Linux OS on your host system. For detailed instructions on installing Clear Linux OS on a bare metal system, follow the bare metal installation instructions.

Before you install any new packages, update Clear Linux OS with the following command:

sudo swupd update

Additionally, you should have:

  • A basic understanding of Linux* and Docker.
  • Clear Linux OS environment that has transparent network access to the Internet. If you are behind a HTTP proxy server, in a corporate setting for example, please refer to the Docker proxy instructions .

Install the containers-basic bundle

Software in Clear Linux OS is offered in the form of 可用的捆绑包 to provide a complete function. The containers-basic provides all the required software packages to run Docker images as containers.

  1. First, install the containers-basic bundle by running this swupd command:

    sudo swupd bundle-add containers-basic

  2. Start the Docker daemon through systemd manager by running this command:

    sudo systemctl start docker

    If you want Docker to start automatically on boot, enable the systemd service by running this command:

    sudo systemctl enable docker

  3. Finally, verify docker has been installed by running this command and checking the version output for both client and server:

    sudo docker version

Congratulations! At this point, you have a working installation of Docker on Clear Linux OS. You are ready to start using container images on your system.

Integration with Kata Containers* (optional)

Kata Containers, is an open source project aiming to increase security of containers by using a hardware-backed virtual machine container runtime rather than software namespace containers that are provided by the standard Docker runc runtime.

Clear Linux OS provides easy integration of the kata-runtime with Docker. More information on installing and using the kata-runtime may be found at Kata Containers*.

注解

The remaining sections of this tutorial are standard to Docker setup and configuration. If you are familiar with Docker basics, you do not need to continue reading. The following sections are provided here for sake of completeness.

Additional Docker configuration

Perform additional Docker daemon configuration via a configuration file typically located at /etc/docker/daemon.json. Clear Linux OS features a 无状态 system so the configuration file daemon.json does NOT exist by default.

  1. Create the daemon.json by running this command:

    sudo touch /etc/docker/daemon.json

    注解

    Refer to the Docker documentation on daemon configuration for the full list of available configuration options and examples.

  2. For production systems, we follow Docker’s recommendation to use the OverlayFS storage driver overlay2, shown below:

    {
   "storage-driver": "overlay2"
}

    注解

    A testing version is found in Docker Device Mapper storage driver. If using this storage driver, a warning message may appear: “usage of loopback devices is strongly discouraged for production use”.

  3. Save and close daemon.json.

  4. Once you’ve made any required changes, be sure to restart the Docker daemon through systemd manager by running this command:

    sudo systemctl restart docker

Pulling and running an image from Docker Hub

Docker Hub is a publically available container image repository which comes pre-configured with Docker. In the example below we will pull and run an the official Docker image for nginx*, an open source reverse proxy server.

  1. First, pull a container image from Docker Hub using the docker pull command. Download the latest nginx* Docker container image by running this command:

    sudo docker pull nginx

  2. Create and launch a new container using the docker run command. Launch a nginx container by running this command:

    sudo docker run --name test-nginx -d -p 8080:80 nginx

    注解

    Below is an explanation of switches used in the command above. For detailed docker run switches and syntax, refer to the Docker Documentation .

    • The –name switch lets you provide a friendly name to target the container for future operations
    • The -d switch launches the container in the background
    • The -p switch allows the container’s HTTP port (80) to be accessible from the Clear Linux OS host on port 8080

  3. You can access the Welcome to Nginx! splash page running in the container by browsing to http://127.0.0.1:8080 or by running this curl command from your Clear Linux OS machine:

    curl 127.0.0.1:8080

  4. Finally, stop and delete the nginx container by running the docker stop and docker rm commands.

    sudo docker stop test-nginx
sudo docker rm test-nginx

Congratulations! At this point, you have successfully pulled a nginx container image from Docker Hub and have run an example container.

Creating a Docker swarm cluster

Clusters of Docker hosts are referred to as swarms.

The process in this tutorial can be repeated to install Docker on multiple Clear Linux OS hosts with the intent to form a Docker swarm cluster.

The Docker documentation on swarm key concepts and Docker documentation on creating a swarm can be referenced for further instructions on setting up a swarm.