我刚刚在EC2上创建了一个Ubuntu实例，但是当我尝试和SSH进入机器时，我得到：
UNPROTECTED PRIVATE KEY FILE! permissions 0644 for 'xxxxx.pem' 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: xxxxx.pem Permission denied (publickey).
如何在没有出现此警告的情况下SSH进入机器？
私钥只能由所有者读取。
在连接的机器上执行chmod 400 xxxxx.pem
