SSH Passwordless Login Using SSH Keygen

Step 1: Create Authentication SSH-Kegen Keys on – (vps1.zetservers.com)

First login into server vps1.zetservers.com with user zetuser and generate a pair of public keys using following command.

[zetuser@zetservers.com ~]$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/zetuser/.ssh/id_rsa): [Press enter key]
Created directory '/home/zetuser/.ssh'.
Enter passphrase (empty for no passphrase): [Press enter key]
Enter same passphrase again: [Press enter key]
Your identification has been saved in /home/zetuser/.ssh/id_rsa.
Your public key has been saved in /home/zetuser/.ssh/id_rsa.pub.
The key fingerprint is:
5f:ad:40:00:8a:d1:9b:99:b3:b0:f8:08:99:c3:ed:d3 zetuser@zetservers.com.com
The key's randomart image is:
+--[ RSA 2048]----+
|        ..oooE.++|
|         o. o.o  |
|          ..   . |
|         o  . . o|
|        S .  . + |
|       . .    . o|
|      . o o    ..|
|       + +       |
|        +.       |
+-----------------+

Step 2: Create .ssh Directory on – vps2.zetservers.com

Use SSH from server vps1.zetservers.com to connect server vps2.zetservers.com using zetuser2 as user and create .ssh directory under it, using following command.

[zetuser@zet ~]$ ssh zetuser2@vps2.zetservers.com mkdir -p .ssh
The authenticity of host 'vps2.zetservers.com (vps2.zetservers.com)' can't be established.
RSA key fingerprint is 45:0e:28:11:d6:81:62:16:04:3f:db:38:02:la:22:4e.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'vps2.zetservers.com' (ECDSA) to the list of known hosts.
zetuser@vps2.zetservers.com's password: [Enter Your Password Here]

Step 3: Upload Generated Public Keys to – vps2.zetservers.com

Use SSH from server vps1.zetservers.com and upload new generated public key (id_rsa.pub) on server vps2.zetservers.com under zetuser2‘s .ssh directory as a file name authorized_keys.

[zetuser@zets ~]$ cat .ssh/id_rsa.pub | ssh zetuser2@vps2.zetservers.com 'cat >> .ssh/authorized_keys'
zetuser2@vps2.zetservers.com's password: [Enter Your Password Here]

Step 4: Set Permissions on – vps2.zetservers.com

Due to different SSH versions on servers, we need to set permissions on .ssh directory and authorized_keys file.

[zetuser@zet ~]$ ssh zetuser2@vps2.zetservers.com "chmod 700 .ssh; chmod 640 .ssh/authorized_keys"
zetuser2@vps2.zetservers.com's password: [Enter Your Password Here]

Step 5: Login from vps1.zetservers.com to vps2.zetservers.com Server without Password

From now onwards you can log into vps2.zetservers.com as zetuser2 user from server vps1.zetservers.com as zetuser1 user without password.

[zetuser@zet ~]$ ssh zetuser2@vps2.zetservers.com

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