Login via SSH without passwd

OpenSSH 的公鑰身份驗證可以讓我們登入遠端主機時，不用再輸入密碼就可以登入遠端主機，同時也完成身份驗證。

做法如下: (紅色部份請依你的環境修改)
以 ssh-keygen 產生公鑰/私鑰對(public-key & private-key)，-t 後面可以是 rsa 或 dsa

$ ssh-keygen -t dsa
Generating public/private dsa key pair.
Enter file in which to save the key (/root/.ssh/id_dsa): idd_dsa
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in idd_dsa.
Your public key has been saved in idd_dsa.pub.
The key fingerprint is:
92:da:70:c9:7e:fe:05:a4:f9:08:c1:1f:cb:24:f0:f0 root@rich-debian

$ scp idd_dsa.pub richman@remote-server-ip:idd_dsa.pub

登入遠端主機，將公鑰加入遠端帳號下~/.ssh/authorized_keys

$ cat idd_dsa.pub >> .ssh/authorized_keys

接下來就可以直接登入遠端主機不用密碼驗證囉!

$ ssh richman@remote-server-ip

2012/3/28 update!
Recommand use:

$ ssh-keygen -t rsa -b 2048