参考：http://www.cnblogs.com/starof/p/4709805.html
https://www.chenyudong.com/archives/ssh-using-private-public-key-no-password.html
http://www.jianshu.com/p/35feb4ff79c5
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Could not load host key: /etc/ssh/ssh_host_ed25519_key in /var/log/auth.log
You can generate the missing hostkey via:
ssh-keygen -A
ed25519 is a bit faster and more secure. It's not necessary and, aside from logspam, this doesn't have that much effect. You could, indeed, comment out HostKey /etc/ssh/ssh_host_ed25519_key, without much effect. But, at the same time, `ed25519 is a good host-key format to support.
可还是ssh连接不上：
客户端：
服务端：
