"Could not load host key" error when xshell connects to the server

Record the problems encountered when configuring the edge server
Reprinted from ：https://www.cnblogs.com/netonline/p/7410586.html

The phenomenon ： start-up sshd The service , Although it seems that the service started successfully , But the client cannot connect sshd Server side . as follows ：

[[email protected] ~]# /usr/sbin/sshd
Could not load host key: /etc/ssh/ssh_host_rsa_key
Could not load host key: /etc/ssh/ssh_host_ecdsa_key
Could not load host key: /etc/ssh/ssh_host_ed25519_key

reason ：

1. From the prompt message, it is sshd The daemons could not load the host key file , Because we can't find these key files ( The configuration file /etc/ssh/sshd_config Key file name and path... Are defined in );
2. commonly openssh After normal service installation , The host will automatically generate the corresponding host key file , But this is not done for unknown reasons , It makes it impossible to remote ssh Connect .
   ps： Check if the key file exists ( Another phenomenon is ： Key file exists , But the file size is 0)：

[[email protected] ~]# ll /etc/ssh/
total 252
-rw-r--r-- 1 root root 242153 Mar 21 22:18 moduli
-rw-r--r-- 1 root root 2208 Mar 21 22:18 ssh_config
-rw------- 1 root root 4361 Mar 21 22:18 sshd_config

Solution , Regenerate the host key file ：
Generate rsa_key (-t Indicates the encryption type used by the generated key ;-f Item followed by the name of the key file to be generated );

[[email protected] ~]# ssh-keygen -t rsa -f /etc/ssh/ssh_host_rsa_key
Generating public/private rsa key pair.
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /etc/ssh/ssh_host_rsa_key.
Your public key has been saved in /etc/ssh/ssh_host_rsa_key.pub.
The key fingerprint is:
5e:2d:19:51:b1:e3:e0:60:65:53:e4:14:f8:d8:38:af [email protected]
The key's randomart image is:
+--[ RSA 2048]----+
| ==Bo |
| o.= . |
| o o=+ |
| . o+*o. |
| S =oo |
| . . .. |
| . . |
| E |
| |
+-----------------+
[[email protected] ~]# ssh-keygen -t ecdsa -f /etc/ssh/ssh_host_ecdsa_key

Generate ecdsa_key;

[[email protected] ~]# ssh-keygen -t ecdsa -f /etc/ssh/ssh_host_ecdsa_key

Generate ed25519_key.

[[email protected] ~]# ssh-keygen -t ed25519 -f /etc/ssh/ssh_host_ed25519_key

The last restart sshd

service ssh restart

Be accomplished