[root@aefe8007a17d ~]# /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

[root@aefe8007a17d ~]# 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

[root@aefe8007a17d ~]# 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 root@aefe8007a17d
The key's randomart image is:
+--[ RSA 2048]----+
|          ==Bo   |
|         o.= .   |
|        o o=+    |
|       . o+*o.   |
|        S =oo    |
|       . . ..    |
|        .  .     |
|          E      |
|                 |
+-----------------+
[root@aefe8007a17d ~]# ssh-keygen -t ecdsa -f /etc/ssh/ssh_host_ecdsa_key

[root@aefe8007a17d ~]# ssh-keygen -t ecdsa -f /etc/ssh/ssh_host_ecdsa_key

[root@aefe8007a17d ~]# ssh-keygen -t ed25519 -f /etc/ssh/ssh_host_ed25519_key

[root@aefe8007a17d ~]# ll /etc/ssh/
total 276
-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    227 May 22 16:48 ssh_host_ecdsa_key
-rw-r--r-- 1 root root    179 May 22 16:48 ssh_host_ecdsa_key.pub
-rw------- 1 root root    411 May 22 16:48 ssh_host_ed25519_key
-rw-r--r-- 1 root root     99 May 22 16:48 ssh_host_ed25519_key.pub
-rw------- 1 root root   1679 May 22 16:48 ssh_host_rsa_key
-rw-r--r-- 1 root root    399 May 22 16:48 ssh_host_rsa_key.pub
-rw------- 1 root root   4361 Mar 21 22:18 sshd_config

[root@localhost ~]# ssh 172.17.0.2
The authenticity of host '172.17.0.2 (172.17.0.2)'can't be established.
ECDSA key fingerprint is 37:2a:69:46:c4:bd:92:b2:43:b4:cc:42:41:8e:12:2e.
Are you sure you want to continue connecting (yes/no)?