记一次sshd无法启动问题排查笔记！

xftp和xshell等工具无法连服务器。连接失败提示：shell authentication failed!一开始想到可能sshd有问题要重启，只能通过阿里云后台的云助手发送命令。

发送命令：service restart sshd 执行失败

The service command supports only basic LSB actions (start, stop, restart, try-restart, reload, force-reload, status). 
For other actions, please try to use systemctl.

根据使用service restart sshd提示要使用/bin/systemctl restart sshd.service，执行后提示：

Job for sshd.service failed because the control process exited with error code. 
See "systemctl status sshd.service" and "journalctl -xe" for details.

systemctl status sshd.service

● sshd.service - OpenSSH server daemon
   Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled; vendor preset: enabled)
   Active: activating (auto-restart) (Result: exit-code) since Wed 2021-07-21 11:04:42 CST; 9s ago
     Docs: man:sshd(8)
           man:sshd_config(5)
 Main PID: 27032 (code=exited, status=255)

Jul 21 11:04:42 DragonersLi systemd[1]: Failed to start OpenSSH server daemon.
Jul 21 11:04:42 DragonersLi systemd[1]: Unit sshd.service entered failed state.
Jul 21 11:04:42 DragonersLi systemd[1]: sshd.service failed.

本打算用宝塔修改/etc/ssh/sshd_config文件，打开密码登录。
根据如上提示信息去百度：Failed to start OpenSSH server daemon.``sshd -t检查执行失败，提示如下：

/etc/ssh/sshd_config line 142: Deprecated option RSAAuthentication
/var/empty/sshd must be owned by root and not group or world-writable.

经查/var/empty/sshd这个目录的属主不是root，所以启动ssh报错！应该是改动过/var目录的权限导致的！

chown root /var/empty/sshd/  #更改目录为root所有
或者：
chown -R root.root /var/empty/sshd
chmod 744 /var/empty/sshd
然后重启sshd服务