ssh 비밀번호 없이 자동로그인 (ssh-keygen)

## 인증키 생성
.ssh]# ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
64:09:73:19:9e:ac:a0:f7:aa:c3:08:f9:0e:5a:fe:61 foo@xxx.org

## 공개키 사용
:.pub 확장자가 붙은 것은 공개키로 이 파일을 접속할 리모트 서버들의 /root/.ssh/ 에 authorized_keys 라는 이름으로 복사해준다.
.ssh]# cp id_rsa.pub authorized_keys
.ssh]# scp id_rsa.pub 아이피:/root/sh/authorized_keys
(chmod 755 /root/.ssh 그리고 chmod 644 .ssh/authorized_keys )

## 인증키 메모리에 상주 시키기
.ssh]# eval $(ssh-agent)
.ssh]# ssh-add


 
[root@www1 /]# scp www1:/root/.ssh/authorized_keys /root/.ssh

서버 새로 등록시 인증키 변경되므로
[root@image2 root]# vi /root/.ssh/known_hosts
30번 서버에서 /root/.ssh/known_hosts 기존등록된것 (www, 아이피 1쌍) 삭제 후 재접속

220.75.202.77 ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAIEA0cnL6foPHWOVb+KDdBGAz8Ru7D+7aCyrEHusMoG9G+FYyHykQ5oSngAY+Qr7jsvAetmvZmLWwT4cGLUwhSbpVW1A0NNwy5UiWQPNT3414RkV63k0TZ19OfYA7zJrJgCjqPXzaXExnsnBSTpQs02cObOk+modpH/4+MjXwP1WmaE=
www17,220.75.202.77 ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAIEAoW/CIyo1u6LBN7Rz/8QwzP9gQ8u2nVcS7yh5AFrRiJx4O1NPCZ/DXLH4QTZgM2+93q7UWXlFSHJ9FGoidH4niECIOtS8dHaiFuutlqxNcqIZiHweJ7y4jZ40umjOWhk/eBweWBdFJlA3ShZaSJ4BvTH+yYbAipUpmhqG2oAvUIM=