配置ssh免密登录时，发现登录不上去，总是要求输入密码，ping是通的。
用root权限查看日志/var/log/secure，可以查到报错
Jun 25 16:50:00 sshd[10957]: Connection closed by 10.25.90.207
Jun 25 16:53:06 sshd[11169]: Authentication refused: bad ownership or modes for file /home/appuser/.ssh/authorized_keys
authorized_keys 这个文件权限不对，改成600权限
chmod 600 /home/appuser/.ssh/authorized_keys