Ubuntu 20.04安裝Docker Engine

使用docker指令前要先安裝Docker Engine，若有需要則先移除舊的docker

sudo apt-get remove docker docker-engine docker.io containerd runc

安裝Docker Engine所需的來源的金鑰

sudo apt-get update
sudo apt-get install \
    apt-transport-https \
    ca-certificates \
    curl \
    gnupg-agent \
    software-properties-common
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
sudo apt-key fingerprint 0EBFCD88

上述指令若成功，終端機會出現

pub   rsa4096 2017-02-22 [SCEA]
      9DC8 5822 9FC7 DD38 854A  E2D8 8D81 803C 0EBF CD88
uid           [ unknown] Docker Release (CE deb) <docker@docker.com>
sub   rsa4096 2017-02-22 [S]

接著安裝Docker的資源庫

sudo add-apt-repository \
   "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
   $(lsb_release -cs) \
   stable"

 完成後安裝Docker Engine

sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io

看docker指令的位置與版本

which docker
docker --version

Docker version 20.10.2, build 2291f61

執行docker指令若出現下面的錯誤訊息

docker: Got permission denied while trying to connect to the Docker daemon socket 
at unix:///var/run/docker.sock: 
Post http://%2Fvar%2Frun%2Fdocker.sock/v1.24/containers/create: 
dial unix /var/run/docker.sock: connect: permission denied.

代表執行docker的權限不足，用下面的指令打開權限

sudo usermod -aG docker $USER

完成後登出系統再重新登入就可使用docker指令了

參考資料

• Install Docker Engine on Ubuntu
• 建立 private 的 Docker Registry 
• [解決方法] docker: permission denied

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