How to set up SSH Key Authentication and disable Password Login on Linux

Situatie

Key-based authentication is more secure than passwords and blocks brute-force attacks against your server.

Requirements: SSH access to the server with an account that has sudo privileges.

Solutie

On your local computer (the client), generate a key pair:

ssh-keygen -t ed25519 -C "email@example.com"

Press Enter to accept the default location and set a passphrase (recommended).

Copy the public key to the server:

ssh-copy-id user@server_address

Test the key-based login in a new terminal window:

ssh user@server_address

If you connect without being asked for the account password (only the key passphrase, if you set one), the key works.

On the server, open the SSH configuration file:

sudo nano /etc/ssh/sshd_config

Set or change the following lines:

PubkeyAuthentication yes
PasswordAuthentication no

Save the file (Ctrl+O, Enter, Ctrl+X) and check the syntax:

sudo sshd -t

Restart the SSH service:

sudo systemctl restart ssh

(on CentOS/RHEL/Fedora the service is called sshd)

Open a new session and verify. A connection attempt without the key must be rejected.

Important: do not close your current SSH session until you have confirmed that the new key-based login works, otherwise you may lock yourself out of the server.

Tip solutie

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