使用下例中ssky-keygen和ssh-copy-id，仅需通过3个步骤的简单设置而无需输入密码就能登录远程Linux主机。
ssh-keygen
创建公钥和密钥。
ssh-copy-id 把本地主机的公钥复制到远程主机的authorized_keys文件上。
ssh-copy-id
也会给远程主机的用户主目录（home）和~/.ssh, 和~/.ssh/authorized_keys设置合适的权限 。

步骤1:
用 ssh-key-gen 在本地主机上创建公钥和密钥
ligh@local-host$ ssh-keygen -t rsa （or dsa）
Enter file in which to save the key (/home/jsmith/.ssh/id_rsa):[Enter
key]
Enter passphrase (empty for no passphrase): [Press enter key]
Enter
same passphrase again: [Pess enter key]
Your identification has been saved in
/home/jsmith/.ssh/id_rsa.
Your public key has been saved in
/home/jsmith/.ssh/id_rsa.pub.
The key fingerprint is:
33:b3:fe:af:95:95:18:11:31:d5:de:96:2f:f2:35:f9

ligh@local-host

步骤2: 用 ssh-copy-id
把公钥复制到远程主机上
ligh@local-host$ ssh-copy-id -i ~/.ssh/id_rsa.pub 
root@192.168.0.3
ligh@remote-host‘s password:
Now try logging into the
machine, with ―ssh ?remote-host‘‖, and check in:
.ssh/authorized_keys to
make sure we haven‘t added extra keys that you weren‘t expecting.
[注:
ssh-copy-id 把密钥追加到远程主机的 .ssh/authorized_key 上.]

步骤3:
直接登录远程主机
ligh@local-host$ ssh remote-host
Last login: Sun Nov 16
17:22:33 2008 from 192.168.1.2
[注: SSH 不会询问密码.]
ligh@remote-host$

[注: 你现在已经登录到了远程主机上]

ssky-keygen + ssh-copy-id 无密码登陆远程LINUX主机