这里同意回复一下，问题解决了！在做了之前的工作都失败的情况下， tail -20 /var/Log/auto.log 发现 userauth_pubkey: key type ssh-dss not in PubkeyAcceptedKeyTypes [preauth] 。。
然后 http://unix.stackexchange.com/questions/247612/ssh-keeps-skipping-my-pubkey-and-asking-for-a-password 这里说的很明白。
> The new openssh version (7.0+) deprecated DSA keys and is not using DSA keys by default (not on server or client). The keys are not preferred to be used anymore, so if you can, I would recommend to use RSA keys where possible.

If you really need to use DSA keys, you need to explicitly allow them in your client config using
``` shell
PubkeyAcceptedKeyTypes +ssh-dss
```
Should be enough to put that line in ~/.ssh/config, as the verbose message is trying to tell you.