【1】将已有的key放在你home目录的.ssh里面
keychain --eval ~/.ssh/id_rsa 运行这个命令
eval `keychain --eval ~/.ssh/id_rsa` 输入后，需要输入一个密码 rd
【2】之前替换了一次id_rsa 、id_rsa.pub、known_hosts，然后再去git clone的时候就会出现输入密码有误；替换成备份的id_rsa 、id_rsa.pub、known_hosts之后，出现以下错误：
WARNING: UNPROTECTED PRIVATE KEY FILE!
Permissions 0644 for '/home/robin/.ssh/id_rsa' are too open.
It is recommended that your private key files are NOT accessible by others.
This private key will be ignored.
bad permissions: ignore key: /home/rd4/.ssh/id_rsa
上面的问题就是这三个文件的权限不对！
解决方案：
chmod 755 ~/.ssh/
chmod 600 ~/.ssh/id_rsa ~/.ssh/id_rsa.pub
chmod 644 ~/.ssh/known_hosts
【3】之后需要输入命令：eval `keychain --eval ~/.ssh/id_rsa`，回车后，需要输入一个密码，这样就可以了。