1. 查看是否已经安装Docker

打开一个terminal控制台，直行 sudo docker run hello-world 命令，若控制台有以下信息输出，则表示docker已经安装了

Hello from Docker!
This message shows that your installation appears to be working correctly.

To generate this message, Docker took the following steps:
 1. The Docker client contacted the Docker daemon.
 2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
    (amd64)
 3. The Docker daemon created a new container from that image which runs the
    executable that produces the output you are currently reading.
 4. The Docker daemon streamed that output to the Docker client, which sent it
    to your terminal.

To try something more ambitious, you can run an Ubuntu container with:
 $ docker run -it ubuntu bash

Share images, automate workflows, and more with a free Docker ID:
 https://hub.docker.com/

For more examples and ideas, visit:
 https://docs.docker.com/get-started/

2. 安装Docker

按照以下步骤进行安装，Docker 安装文档

Installation methods
You can install Docker Engine in different ways, depending on your needs:

Most users set up Docker’s repositories and install from them, for ease of installation and upgrade tasks. This is the recommended approach.

Some users download the DEB package and install it manually and manage upgrades completely manually. This is useful in situations such as installing Docker on air-gapped systems with no access to the internet.

In testing and development environments, some users choose to use automated convenience scripts to install Docker.

• Install using the repository
• Install from a package
• Install using the convenience script
  ``

本文使用Install using the repository方法安装

$ apt-cache madison docker-ce

 docker-ce | 5:19.03.12~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:19.03.11~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:19.03.10~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:19.03.9~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:19.03.8~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:19.03.7~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:19.03.6~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:19.03.5~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:19.03.4~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:19.03.3~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:19.03.2~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:19.03.1~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:19.03.0~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:18.09.9~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:18.09.8~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:18.09.7~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:18.09.6~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:18.09.5~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:18.09.4~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:18.09.3~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:18.09.2~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:18.09.1~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 5:18.09.0~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 18.06.3~ce~3-0~ubuntu | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 18.06.2~ce~3-0~ubuntu | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 18.06.1~ce~3-0~ubuntu | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 18.06.0~ce~3-0~ubuntu | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 18.03.1~ce-0~ubuntu | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 18.03.0~ce-0~ubuntu | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 17.12.1~ce-0~ubuntu | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 17.12.0~ce-0~ubuntu | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 17.09.1~ce-0~ubuntu | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 17.09.0~ce-0~ubuntu | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 17.06.2~ce-0~ubuntu | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 17.06.1~ce-0~ubuntu | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 17.06.0~ce-0~ubuntu | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 17.03.3~ce-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 17.03.2~ce-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 17.03.1~ce-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
 docker-ce | 17.03.0~ce-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages

我选择的是最新的是第一个 “5:19.03.10_3-0ubuntu-xenial”，执行以下指令完成安装：

$ sudo apt-get install docker-ce=5:19.03.10~3-0~ubuntu-xenial docker-ce-cli=5:19.03.10~3-0~ubuntu-xenial containerd.io

执行以下指令测试是否安装成功：

$ sudo docker run hello-world

安装完成之后的docker只有root用户可以使用，其他用户使用时只能加sudo。在网页中，可以看到以下内同，在Install from a package之后：

Docker Engine is installed and running. The docker group is created but no
users are added to it. You need to use sudo to run Docker commands. Continue to
Post-installation steps for Linux to allow non-privileged users to run Docker
commands and for other optional configuration steps.

点击 Post-installation steps for Linux进入新的页面，执行相关配置。

给当前用户配置超级用户访问权限

Create the docker group.
$ sudo groupadd docker

Add your user to the docker group.
$ sudo usermod -aG docker $USER