本文翻译自docker官网：https://docs.docker.com/engine/install/centos/

Install Docker Engine on CentOS

To get started with Docker Engine on CentOS, make sure you
meet the prerequisites, then
install Docker.

要开始在CentOS上使用Docker引擎，请确保满足先决条件，然后安装Docker。

Prerequisites

OS requirements

To install Docker Engine, you need a maintained version of CentOS 7 or 8.
Archived versions aren't supported or tested.

若要安装Docker引擎，你需要CentOS 7或8的维护版本。不支持或测试存档版本。

The centos-extras repository must be enabled. This repository is enabled by
default, but if you have disabled it, you need to
re-enable it

必须启用centos-extras存储库。默认情情况下，此存储库处于开启状态，但如果你已禁用它，你需要重新启用它。

The overlay2 storage driver is recommended.

建议使用overlay2存储驱动程序。

Uninstall old versions

Older versions of Docker were called docker or docker-engine. If these are
installed, uninstall them, along with associated dependencies.

旧版本的docker称为docker或docker-engine。如果安装了这些，请卸载它们以及相关依赖项。

$ sudo yum remove docker \
                  docker-client \
                  docker-client-latest \
                  docker-common \
                  docker-latest \
                  docker-latest-logrotate \
                  docker-logrotate \
                  docker-engine

It's OK if yum reports that none of these packages are installed.

如果yum报告没有安装这些包就OK了。

The contents of /var/lib/docker/, including images, containers, volumes, and
networks, are preserved. The Docker Engine package is now called docker-ce.

/var/lib/docker/的内容（包括镜像、容器、卷、网络）将被保留。Docker引擎包现在成为docker-ce

Installation methods

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

你可以根据需要以不同的方式安装Docker Engine：

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

大多数用户设置Docker的repositories并从中安装，以便安装和升级任务。这是推荐的方法。
Some users download the RPM 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.

有些用户下载RPM包并手动安装，完全手动管理升级。这在一些情况下很有用，比如在没有互联网接入的air-gapped（气隙）系统上安装Docker。
In testing and development environments, some users choose to use automated
convenience scripts to install Docker.

在测试和开发环境中，一些用户选择使用自动化的便利脚本来安装Docker。

Install using the repository

Before you install Docker Engine for the first time on a new host machine, you need
to set up the Docker repository. Afterward, you can install and update Docker
from the repository.

在一台新的主机上首次安装Docker Engine之前，你需要设置Docker的repository。然后，你可以从该repository安装和更新Docker。

Set up the repository

Install the yum-utils package (which provides the yum-config-manager
utility) and set up the stable repository.

安装yum-utils包（它提供了yum config manager实用程序）并且设置稳定的repository。

$ sudo yum install -y yum-utils

$ sudo yum-config-manager \
    --add-repo \
    {{ download-url-base }}/docker-ce.repo

Install Docker Engine

Install the latest version of Docker Engine and containerd, or go to the next step to install a specific version:

安装最新版本的Docker Engine和contianerd，或者转至下一步安装特定版本的：
```
$ sudo yum install docker-ce docker-ce-cli containerd.io
```
If prompted to accept the GPG key, verify that the fingerprint matches
060A 61C5 1B55 8A7F 742B 77AA C52F EB6B 621E 9F35, and if so, accept it.

如果提示接受GPG秘钥，验证指纹是否与060A 61C5 1B55 8A7F 742B 77AA C52F EB6B 621E 9F35相匹配，如果匹配，接受它。

Docker is installed but not started. The docker group is created, but no users are added to the group.

Docker已经安装但是并没有启动。docker组已经创建，但是没有用户加到该组。
To install a specific version of Docker Engine, list the available versions
in the repo, then select and install:

要安装特定版本的Docker Engine，在repo中列出所有可用版本，然后选择并安装：

a. List and sort the versions available in your repo. This example sorts
results by version number, highest to lowest, and is truncated:

列出并排序repo中可用的版本。此例子通过版本号排序结果，从高到底，并被截断：
```
$ yum list docker-ce --showduplicates | sort -r

docker-ce.x86_64  3:18.09.1-3.el7                     docker-ce-stable
docker-ce.x86_64  3:18.09.0-3.el7                     docker-ce-stable
docker-ce.x86_64  18.06.1.ce-3.el7                    docker-ce-stable
docker-ce.x86_64  18.06.0.ce-3.el7                    docker-ce-stable
```
The list returned depends on which repositories are enabled, and is specific
to your version of CentOS (indicated by the .el7 suffix in this example).

返回列表取决于你启用了哪些repositories，并且特定于你的CentOS版本（在本例中以.el7后缀表示）

b. Install a specific version by its fully qualified package name, which is
the package name (docker-ce) plus the version string (2nd column)
starting at the first colon (:), up to the first hyphen, separated by
a hyphen (-). For example, docker-ce-18.09.1.

按其完全限定的软件包名称（即软件包名称（docker ce）加上版本字符串（第2列），从第一个冒号（：）开始，一直到第一个连字符，用连字符（-）分隔）安装特定版本。例如，docker-ce-18.09.1
```
$ sudo yum install docker-ce-<VERSION_STRING> docker-ce-cli-<VERSION_STRING> containerd.io
```
Docker is installed but not started. The docker group is created, but no users are added to the group.

Docker已经安装但是并没有启动。docker组已经创建，但是没有用户加到该组。
Start Docker.
```
$ sudo systemctl start docker
```
Verify that Docker Engine is installed correctly by running the hello-world
image.

通过运行hello-world镜像来验证Docker Engine是否安装正确。
```
$ sudo docker run hello-world
```
This command downloads a test image and runs it in a container. When the
container runs, it prints an informational message and exits.

该指令下载一个测试镜像并在一个容器内运行它。当容器运行时，它会打印一个信息性的消息并退出。

Docker Engine is installed and running. You need to use sudo to run Docker
commands. Continue to Linux post install to allow
non-privileged users to run Docker commands and for other optional configuration
steps.

Docker Engine已经安装完成并运行。你需要使用sudo来运行Docker指令。
继续Linux post install 以允许非特权用户运行Docker指令和其它可选配置步骤。

Upgrade Docker Engine

To upgrade Docker Engine, follow the installation instructions,
choosing the new version you want to install.

跟随installation instructions 选择你想要安装的新版本来更新Docker Engine。

CentOS 安装 Docker