How to disable password based login in Linux

It’s quite easy to disable the password based login in the SSH. Before you proceed check if you have prepared the system to logon without password.

• You have a user other than root, who can enter the remote server. If not, take a look into my article How to disable root login
• Please check if that user has sufficient permissions if you use an existing user. # usermod -aG sudo user
• You have created an ssh key on your local machine and shared the key with the remote server. If not, take a look into my article Configure SSH login without password

Now, no prompt is asking you for a password, but you are still able to do it. You can test it by using the following command for login:

# ssh user@servername -o PubkeyAuthentication=no

To disable the password log in at all you need to edit the following file:

# sudo editor /etc/ssh/sshd_config

Find the property and change the value

 PasswordAuthentication no 

The last step is to restart the ssh service and your change will take action with the following command:

# sudo systemctl reload ssh

If you try to login with the option -o PubkeyAuthentication=no you’re not allowed to do this.

# user@servername: Permission denied (publickey).