I have realised that I had two keys in my VPS and I wasn’t sure which one it was used when I was ssh-ing so I had to search a bit to find out.
These two links cover the process:
1- You need to increase the logging of your sshd (destination – server)
server# vim /etc/ssh/sshd_config LogLevel VERBOSE server# service sshd restart server# tail -f /var/log/auth.log
2- From client, just ssh as usual to the server and check auth.log as per above
Jul 3 14:17:55 server sshd[8600]: Connection from IPV6 port 57628 on IPV6::453 port 64022 Jul 3 14:17:55 server sshd[8600]: Postponed publickey for client from IPv6 port 57628 ssh2 [preauth] Jul 3 14:17:55 server sshd[8600]: Accepted publickey for client from IPv6 port 57628 ssh2: ED25519 SHA256:BtOAX9eVpFJJgJ5HzjKU8E973m+MX+3gDxsm7eT/iEQ Jul 3 14:17:55 server sshd[8600]: pam_unix(sshd:session): session opened for user client by (uid=0) Jul 3 14:17:55 server sshd[8600]: User child is on pid 8606 Jul 3 14:17:55 server sshd[8606]: Starting session: shell on pts/7 for client from IPv6 port 57628 id 0
3- So we have the fingertip of the key used by client. Now we need to get the fingertips of our clients keys to find the match:
client $ ssh-keygen -l -f ~/.ssh/id_ed25519.pub 256 SHA256:BtOAX9eVpFJJgJ5HzjKU8E973m+MX+3gDxsm7eT/iEQ client@local (ED25519)
4- So the we can see that I am using my id_ed25519.pub key to connect to the server