EC2 접속 ssh -i ./pem키 ubuntu@ec2주소권한 오류가 뜬다면? Permission denied (publickey) chmod 400 pem키 Docker 설치 오래된 버전 삭제sudo apt-get remove docker docker-engine docker.io containerd runcRepository 설정sudo apt-get updatesudo apt-get install ca-certificates curl gnupg lsb-releasecurl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpgecho..