mkdir -p $HOME/.ssh
chmod 0700 $HOME/.ssh

Create the key pair :

~> ssh-keygen -t rsa -b 4096 -f ~/.ssh/VM115.key -C "OpenSuse-VM-Server"
Generating public/private rsa key pair.
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/ms/.ssh/VM115.key.
Your public key has been saved in /home/ms/.ssh/VM115.key.pub.
The key fingerprint is:
SHA256:j4yPQaH1De1nsRbg/V3wMWEVrnHtU9bAPfm4bUcNgD0 OpenSuse-VM-Server
The key's randomart image is:
+---[RSA 4096]----+
|          .o.ooB*|
|         o.oE =**|
|      o . o +o =@|
|     o o +   ==+*|
|    . . S o =..=o|
|     . o o +  . =|
|      o o .    ..|
|       +         |
|      . .        |
+----[SHA256]-----+

Install the public key in remote server :

ms@localhost:~> ssh-copy-id -i /home/ms/.ssh/VM115.key.pub max3@192.168.1.115
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/home/ms/.ssh/VM115.key.pub"
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
Password: 

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh 'max3@192.168.1.115'"
and check to make sure that only the key(s) you wanted were added.


 Disable the password based login on a server:
max:/home/max3 # nano /etc/ssh/sshd_config
PasswordAuthentication no 
PermitEmptyPasswords no
=> ACHTUNG : PermitRootLogin no => use sudo max3
UsePAM no 


max2@install:~> sudo rcsshd restart

----------------------------------
sudo zypper install fail2ban
sudo nano /etc/fail2ban/jail.conf