Managing SSH keys: adding and removing

Summary

SSH keys allow passwordless server login and improve security. Below: how to generate a key, add it to the server, and disable password login.

Applies to:
✔ VPS
✔ Dedicated servers
✔ Linux, macOS, Windows

Generating a key

Linux/macOS

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

Or RSA:

ssh-keygen -t rsa -b 4096

Windows (PowerShell)

ssh-keygen -t ed25519

Adding the key to the server

Automatically

ssh-copy-id -i ~/.ssh/id_ed25519.pub root@SERVER_IP

Manually

cat ~/.ssh/id_ed25519.pub

mkdir -p /root/.ssh

echo "PUBLIC_KEY_CONTENT" >> /root/.ssh/authorized_keys

chmod 700 /root/.ssh

chmod 600 /root/.ssh/authorized_keys

Removing a key

Edit authorized_keys on the server and remove the line with the unwanted key:

nano /root/.ssh/authorized_keys

Disabling password login

Before disabling passwords, make sure key-based login works! Otherwise you'll lose server access.

In /etc/ssh/sshd_config:

PasswordAuthentication no
PubkeyAuthentication yes

systemctl restart sshd

Verification

ssh root@SERVER_IP

Should connect without a password prompt.

If key login doesn't work, check permissions on ~/.ssh (700) and authorized_keys (600). If locked out, connect via VNC/IPMI console.