generate_SSH_KEY.md

Linux generate SSH Key

The SSH supports different kinds of authentication techniques. One of the most common mechanisms is password authentication, and the other one is public-key-based authentication. In both, the public key-based authentication is more secure and convenient than the password authentication method and based on digital signatures.

Verify SSH Key if exist

$ ls -l ~/.ssh/id_*.pub

Generate new SSH key pair

If you will receive an error saying No such file or directory then, it means you don’t have an SSH key on your machine.

$ ssh-keygen -t rsa -b 4096 -C "[email protected]"

then answer several questions. Notes: just leave passphrase empty .

Verify SSH key pair generated

$ ls ~/.ssh/id_*
/home/sudiman/.ssh/id_rsa  /home/sudiman/.ssh/id_rsa.pub

Copy the public key to Ubuntu remote server

Copy with ssh-copy-id

$ ssh-copy-id your_username@your_host

Replace your_username and your_host with yours.

Manual Copy to the Server

$ cat ~/.ssh/id_rsa.pub | ssh your_username@your_host "mkdir -p ~/.ssh && chmod 700 ~/.ssh && cat >> ~/.ssh/authorized_keys && chmod 600 ~/.ssh/authorized_keys"

Replace your_username and your_host with yours.

Try to Log in with the SSH key on a remote server

$ ssh your_username@your_host

Disable SSH password authentication

In this step, you will disable the SSH password authentication to add an extra layer of security. Before disable, make sure that the user, which is login, has sudo privileges or a root account on this server. First, login into your remote server with a root account or sudo privileges. Now, open the ‘/etc/ssh/sshd_config’ SSH configuration file by executing the below-given command:

$ sudo vi /etc/ssh/sshd_config

Find the PasswordAuthentication configuration line and set it with a ‘no’ argument.

PasswordAuthentication no

Exit and restart SSH Service

$ sudo systemctl restart ssh