Ubuntu – How to delete useless ssh key on the server(Ubuntu server 16.04) and generate new one

keyboardserverssh

I have accidentally lost my ~/.ssh/known_hosts file. on my server, I had disabled ssh with a password. I still able to plug a screen on my server and log in with the keyboard. How can I remove last ssh key (from my server) since it is not useful anymore? How can I regenerate new ssh private key transfer into my laptop (Linux)?

Thank you in advance

ssh -V = OpenSSH_7.2p2 Ubuntu-4ubuntu2.2, OpenSSL 1.0.2g ...

Best Answer

The key will be in ~/.ssh/authorized_keys

You can delete the line for the old key with the editor of your choice.

You can generate a new private key by running the following command on a client machine.

ssh-keygen

Depending on which algorithm was used add the contents of the ~/.ssh/id*.pub file to the ~/.authorized_keys file on the server. It will be a single line

It is probably called:

id_rsa.pub

And the key will look like

ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAIZ5CYnbANePH8y1rKvFIpWNWrr3kSuelNP61W/yPiPtf11DZgdWsP5eaBQQqEZpXnw57pu5SuPHe5FPn+L39c/xtPJdvn1ZSVo1OTWMPkKGX+5WuL5ypaHN5J2E4qkZD9vzQ4OcUGGdODZ676TPV5cAD7oYHvBWKdCxPUztUAAAADAQABAAIZ5CYnbANePH8y1rKvFIpWNWrr3kSuelNP6 user@foo

Note that it is a single line. If you delete the authorized_keys file on the server you will need to make sure the permissions are correct.

chmod 0644 ~/.ssh/authorized_keys
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