前言
ubuntu20.4安装docker官网主要步骤如下：
先删除之前的版本
$ sudo apt-get remove docker docker-engine docker.io containerd runc
使用阿里云源
可以先备份一下，然后编辑，复制阿里源进去，保存！
sudo mv /etc/apt/sources.list /etc/apt/sources.list.bak
sudo gedit /etc/apt/sources.list
阿里源：
deb http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse
检查并更新
sudo apt update
sudo apt upgrade
安装docker
sudo apt-get install docker-ce docker-ce-cli containerd.io
安装的过程很慢，需要耐心等待一下
安装完毕
运行docker，开启
sudo docker run hello-world`
运行helloworld
sudo docker run hello-world
