[Docker] 도커 설치 - Ubuntu 18.04

# 오래된 버전 삭제
sudo apt-get remove docker docker-engine docker.io docker-ce
# docker install
sudo apt-get update
# docker 필수 패키지
sudo apt-get install -y apt-transport-https ca-certificates curl software-properties-common
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add 
# armhf는 [arch=armhf], s390x는 [arch=s390x]로 명령어를 변경해야 합니다.
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
sudo apt update

# 설치 가능한 버전 확인
apt-cache policy docker-ce
		  docker-ce:
		  Installed: (none)
		  Candidate: 18.06.1~ce~3-0~ubuntu
		  Version table:
		  18.06.1~ce~3-0~ubuntu 500
		  500 https://download.docker.com/linux/ubuntu bionic/stable amd64 Packages
		  18.06.0~ce~3-0~ubuntu 500
	  	500 https://download.docker.com/linux/ubuntu bionic/stable amd64 Packages
		  18.03.1~ce~3-0~ubuntu 500
  		500 https://download.docker.com/linux/ubuntu bionic/stable amd64 Packages
sudo apt-get install -y docker-ce

# docker status 확인
sudo systemctl status docker
		  ● docker.service - Docker Application Container Engine
		  Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
		  Active: active (running) since Fri 2018-08-24 07:20:49 UTC; 51s ago
		  Docs: https://docs.docker.com
		  Main PID: 4527 (dockerd)
		  Tasks: 18
		  CGroup: /system.slice/docker.service
		  ├─4527 /usr/bin/dockerd -H fd://
  		└─4549 docker-containerd --config /var/run/docker/containerd/containerd.toml

### systemctl command not found 에러 발생했을 때
sudo apt-get install systemd
sudo apt-get purge docker-ce
sudo rm -rf /var/lib/docker
sudo rm -rf /etc/docker
sudo apt-get remove docker docker-engine docker.io containerd runc

# docker root directory 변경
vi /lib/systemd/system/docker.service

# ExecStart=/usr/bin/dockerd -H fd://
ExecStart=/usr/bin/dockerd -g PATH 	<- 변경하려는 경로

# docker restart
systemctl daemon-reload
service docker restart
docker info

# docer registry server 변경
vi /etc/docker/daemon.json
	---------------------------------------------------------		
	{
	    "insecure-registries": ["XXX.XXX.XXX.XXX:port"]		
	}
	---------------------------------------------------------		
	service docker restart