UbuntuにDockerを入れる

#はじめに
dockerのインストール方法には３種類ある。
1 Dockerリポジトリーを使う方法
2 debパッケージを使う方法
3 スクリプトを用いてインストールする方法

#2のリポジトリーを使う方法
##パッケージの更新

sudo apt-get update

##必要なソフトウェアのインストール
sudo apt-get install -y
apt-transport-https
ca-certificates
curl
gnupg-agent
software-properties-common

##GPGキーを追加
GPGキーとはGNU Privacy Guardという暗号化ソフトで生成される公開鍵である。
https://xtech.nikkei.com/it/article/Keyword/20091204/341579/

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
sudo apt-key fingerprint 0EBFCD88

#dockerエンジンをinstall

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

正常にinstallできたかの確認

sudo docker run hello-world

Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
0e03bdcc26d7: Pull complete
Digest: sha256:d58e752213a51785838f9eed2b7a498ffa1cb3aa7f946dda11af39286c3db9a9
Status: Downloaded newer image for hello-world:latest

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/

#参考
https://docs.docker.com/engine/install/ubuntu/