How To Setup SSH Public Key Authentication On Linux

Why using SSH Public Key Authentication On Linux? Public Key Authentication is much more secure than SSH password authentication.
In case if your server allows password authentication, remote attackers will try guess your SSH password with brute-force attacks.

$ cd
$ mkdir .ssh
$ chmod 0700 .ssh

Generate SSH key pair

On the client computer generate key pair with command:

$ ssh-keygen -t rsa -C "Comment"

You can type file name or just hit enter button. Also hit twice enter button for empty passphrase:

Now you have generated key pair in .ssh folder.

id_rsa Private Key (DO NOT SHARE)
id_rsa.pub Public Key

Install generated public key onto remote server

$ ssh-copy-id -i $HOME/.ssh/id_rsa.pub username@YourRemoteServer

Sample output:

Source of key(s) to be installed: "****/id_rsa.pub"
attempting to log in with the new key(s), to filter out any that are already installed
1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
[email protected]'s password:

Number of key(s) added: 1

Now try logging into the machine, with: "ssh 'username@YourRemoteServer'"
and check to make sure that only the key(s) you wanted were added.

Now try logging into the machine

ssh 'username@username@YourRemoteServer

Disable ssh password login on Linux

Edit SSH server configuration file sshd_config:

vi /etc/ssh/sshd_config

Find in config file and edit next parameters:

ChallengeResponseAuthentication no
PasswordAuthentication no
UsePAM no
PermitRootLogin no

Save and restart SSH server:

# /etc/init.d/ssh restart

# systemctl restart ssh

Now test to to login with next command:

$ ssh [email protected] -o PubkeyAuthentication=no

Sample output:

Permission denied (publickey).

How To Setup SSH Public Key Authentication On Linux