How to enable passwordless SSH login

/ DevOps, linux / By

SSH is a secure protocol for logging in to remote servers over the network. To improve security and prevent unauthorised logins, SSH allows you to log in using public key authentication. I’ll show you how to set it up in this post.

Generate SSH Keys

Step 1, generate an SSH key pair

# Generate keys if you don't already have one
ssh-keygen -t ed25519  -C "your_email@domain.com"

Next, copy the public key to the remote server:

# Linux: Copy public key contents on host server to remote server
ssh-copy-id remote_username@server_ip_address

If your system does not have the ssh-copy-id tool, copy the contents of the public key(file that ends in .pub) manually and paste them into the .ssh/authorized_keys files in the remote server.

# Windows does not have ssh-copy-id, copy pub key contents manually to:
vim ~/.ssh/authorized_keys

Disable SSH Password Authentication

For additional security, consider disabling password authentication via SSH. Do this only after verifying you can SSH into the server without being prompted for a password. SSH into the remote server and edit its SSH configuration

ssh user@server_ip_address

Open the SSH config file at /etc/ssh/sshd_config and find and change these settings to the values below:

# /etc/ssh/sshd_config
PasswordAuthentication no
ChallengeResponseAuthentication no
UsePAM no

Doing this disables all other authentication methods except SSH keys.

Disable Root login

Allowing direct root access to your server over SSH can open you up to malicious users who may brute force your root password and potentially gain access to your server if the password can be guessed. Disabling root login over SSH after setting up Key-based authentication is good practice.

To disable Root SSH Login, edit the /etc/ssh/sshd_config file and locate the PermitRootLogin line and uncomment and change it to:

PermitRootLogin no

Save and close the file.

Restart SSH:

sudo systemctl restart ssh

in CentOS/Fedora:

sudo systemctl restart sshd

Conclusion

This article showed you how to connect to remote servers without being prompted for a password using SSH Keys and also showed you how to secure your server by disabling SSH using the root user.