問題現象：
發現本機sshd服務開啟但是其他機器不能登陸
查看sshd服務
[root@localhost ~]# systemctl status sshd.service ● sshd.service - OpenSSH server daemon Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled; vendor preset: enabled) Active: active (running) since Sun 2017-06-18 03:55:51 PDT; 21min ago Docs: man:sshd(8) man:sshd_config(5) Process: 3789 ExecStart=/usr/sbin/sshd $OPTIONS (code=exited, status=0/SUCCESS) Main PID: 3791 (sshd) CGroup: /system.slice/sshd.service └─3791 /usr/sbin/sshd Jun 18 04:17:07 localhost.localdomain sshd[4304]: error: bad permissions: ignore key: /etc/ssh/ssh_host_ecdsa_key Jun 18 04:17:07 localhost.localdomain sshd[4304]: error: Could not load host key: /etc/ssh/ssh_host_ecdsa_key Jun 18 04:17:07 localhost.localdomain sshd[4304]: error: @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ Jun 18 04:17:07 localhost.localdomain sshd[4304]: error: @ WARNING: UNPROTECTED PRIVATE KEY FILE! @ Jun 18 04:17:07 localhost.localdomain sshd[4304]: error: @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ Jun 18 04:17:07 localhost.localdomain sshd[4304]: error: Permissions 0604 for '/etc/ssh/ssh_host_ed25519_key' are too open. Jun 18 04:17:07 localhost.localdomain sshd[4304]: error: It is required that your private key files are NOT accessible by others. Jun 18 04:17:07 localhost.localdomain sshd[4304]: error: This private key will be ignored. Jun 18 04:17:07 localhost.localdomain sshd[4304]: error: bad permissions: ignore key: /etc/ssh/ssh_host_ed25519_key Jun 18 04:17:07 localhost.localdomain sshd[4304]: error: Could not load host key: /etc/ssh/ssh_host_ed25519_key
解決方法：可以很容易看出來這是因為ssh服務的配置文件的訪問權限有問題，配置文件路徑為/etc/ssh，將這些文件的權限修改為如下即可:
[root@localhost ssh]# ls -al total 288 drwxr-xr-x. 2 root root 225 Jun 18 03:55 . drwxr-xr-x. 138 root root 8192 Jun 18 03:54 .. -rw-r--r--. 1 root root 242153 Nov 11 2016 moduli -rw-r--r--. 1 root root 2208 Nov 11 2016 ssh_config -rw-r--r-- 1 root root 4362 Jun 18 03:55 sshd_config -rw-------. 1 root ssh_keys 227 May 31 18:43 ssh_host_ecdsa_key -rw-r--r--. 1 root root 162 May 31 18:43 ssh_host_ecdsa_key.pub -rw-------. 1 root ssh_keys 387 May 31 18:43 ssh_host_ed25519_key -rw-r--r--. 1 root root 82 May 31 18:43 ssh_host_ed25519_key.pub -rw-------. 1 root ssh_keys 1679 May 31 18:43 ssh_host_rsa_key -rw-r--r--. 1 root root 382 May 31 18:43 ssh_host_rsa_key.pub [root@localhost ssh]#