OpenSSH : SSH Key-Pair Authentication

Configure SSH server to login with Key-Pair Authentication.

Create a private key for client and a public key for server to do it.

[1]. Create Key-Pair by each user, so login with a common user on SSH Server Host and work like follows.

# create key-pair

[cent@dlp ~]$ ssh-keygen

Generating public/private rsa key pair.

Enter file in which to save the key (/home/cent/.ssh/id_rsa):   # Enter or input changes if you want

Created directory '/home/cent/.ssh'.

Enter passphrase (empty for no passphrase):   # set passphrase (if set no passphrase, Enter with empty)

Enter same passphrase again:

Your identification has been saved in /home/cent/.ssh/id_rsa.

Your public key has been saved in /home/cent/.ssh/id_rsa.pub.

The key fingerprint is:

SHA256:+EGzR05q/tnbBNmyaPOfsipDYz9ZAD6OrH4VmzfssPY cent@dlp.srv.world

The key's randomart image is:

.....

.....

[cent@dlp ~]$ ll ~/.ssh

total 8

-rw-------. 1 cent cent 1876 Sep 29 20:34 id_rsa

-rw-r--r--. 1 cent cent  400 Sep 29 20:34 id_rsa.pub

[cent@dlp ~]$ mv ~/.ssh/id_rsa.pub ~/.ssh/authorized_keys

[2]. Transfer the private key created on the Server to a Client, then it's possbile to login with Key-Pair authentication.

[cent@node01 ~]$ mkdir ~/.ssh

[cent@node01 ~]$ chmod 700 ~/.ssh

# transfer the private key to the local ssh directory

[cent@node01 ~]$ scp cent@dlp.srv.world:/home/cent/.ssh/id_rsa ~/.ssh/

cent@dlp.srv.world's password:

id_rsa                                        100% 1876   193.2KB/s   00:00

[cent@node01 ~]$ ssh cent@dlp.srv.world

Enter passphrase for key '/home/cent/.ssh/id_rsa':   # passphrase if you set

Activate the web console with: systemctl enable --now cockpit.socket

Last login: Sun Sep 29 20:33:58 2019

[cent@dlp ~]$   # logined

[3]. If you set [PasswordAuthentication no], it's more secure.

[root@dlp ~]# vi /etc/ssh/sshd_config

# line 73: change to [no]

PasswordAuthentication no

[root@dlp ~]# systemctl restart sshd

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