SSH Keys

SSH keys are more secure than passwords and more convenient: no more credential entry at each access.

How It Works

You generate a key pair:

• Private key: stays on your computer (never share)
• Public key: goes on server

1. Generate Key Pair

On Linux / macOS / Windows (PowerShell):

ssh-keygen -t ed25519 -C "my-server-key"

You'll be asked where to save key (press Enter for default ~/.ssh/id_ed25519) and optional passphrase.

2. Copy Public Key to Server

ssh-copy-id root@SERVER_IP

If SSH port is different from 22:

ssh-copy-id -p PORT root@SERVER_IP

Manual alternative (if ssh-copy-id not available):

cat ~/.ssh/id_ed25519.pub | ssh root@SERVER_IP "mkdir -p ~/.ssh && cat >> ~/.ssh/authorized_keys && chmod 600 ~/.ssh/authorized_keys"

3. Verify It Works

ssh root@SERVER_IP

If connection works without password, keys are configured correctly.

4. Disable Password Access (optional but recommended)

Once verified keys work, disable login via password:

nano /etc/ssh/sshd_config

Find and set:

PasswordAuthentication no
PermitRootLogin prohibit-password

Restart SSH:

systemctl restart sshd

Manage Multiple Keys (SSH Config)

If you have multiple servers, create ~/.ssh/config to manage them easily:

Host my-vps
    HostName SERVER_IP
    User root
    Port 22
    IdentityFile ~/.ssh/id_ed25519

Host other-server
    HostName OTHER_SERVER_IP
    User ubuntu
    Port 2222
    IdentityFile ~/.ssh/id_ed25519

Then access simply with:

ssh my-vps