1. sudo dnf config-manager --add-repo=https://download.docker.com/linux/centos/docker-ce.repo
    2. sudo dnf install https://download.docker.com/linux/centos/7/x86_64/stable/Packages/containerd.io-1.2.6-3.3.el7.x86_64.rp
    3. dnf list docker-ce --showduplicates | sort -r
    4. # sudo dnf install docker-ce-3:18.09.1-3.el7
    5. sudo dnf install docker-ce
    6. # 如过出现如下错误，则运行
    7. # Problem: package docker-ce-3:19.03.2-3.el7.x86_64 requires containerd.io >= 1.2.2-3, but none of the providers can be installed
    8. # sudo dnf install --nobest docker-ce