$ssh-keygen -t rsa
$ssh-copy-id -i ~/.ssh/id_rsa.pub user@server
等同于：
$ssh-keygen -t rsa
$cat ~/.ssh/id_rsa.pub | ssh user@server "cat - >> ~/.ssh/authorized_keys"
$ssh-keygen -t rsa
$ssh-copy-id -i ~/.ssh/id_rsa.pub user@server
等同于：
$ssh-keygen -t rsa
$cat ~/.ssh/id_rsa.pub | ssh user@server "cat - >> ~/.ssh/authorized_keys"