SSH Keys

SSH keys provide secure, passwordless authentication to your cloud instances. Instead of typing a password every time you connect, your SSH key pair handles authentication automatically — it is both more secure and more convenient.

Why Use SSH Keys

Supported Formats

Generating an SSH Key

If you do not already have an SSH key, generate one on your local machine.

Ed25519 (Recommended)

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

RSA (Compatibility)

ssh-keygen -t rsa -b 4096 -C "your-email@example.com"

When prompted:

1. File location — Press Enter to accept the default (~/.ssh/id_ed25519 or ~/.ssh/id_rsa)
2. Passphrase — Enter a passphrase for additional security (recommended) or press Enter for no passphrase

This creates two files:

Viewing Your Public Key

cat ~/.ssh/id_ed25519.pub

Output looks like:

ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAI... your-email@example.com

Uploading a Key to HUC

1. Navigate to your cloud dashboard → SSH Keys
2. Click Add SSH Key
3. Paste the contents of your public key file (~/.ssh/id_ed25519.pub)
4. Give the key a recognizable name (e.g., work-laptop, ci-deploy)
5. Click Save

Your key is now available for selection when creating new instances.

Selecting Keys During Instance Creation

When creating a new cloud instance:

1. In the Authentication section, select one or more SSH keys from your uploaded keys
2. The selected keys are injected into the instance's ~/.ssh/authorized_keys file on first boot
3. You can select multiple keys to grant access to several users or machines

Connecting to Your Instance

Once your instance is running with your SSH key configured:

# Connect as root (default)
ssh root@your-instance-ip

# Connect with a specific key file
ssh -i ~/.ssh/id_ed25519 root@your-instance-ip

If you set a passphrase on your key, you will be prompted to enter it. Use ssh-agent to avoid entering it repeatedly:

# Start the SSH agent
eval "$(ssh-agent -s)"

# Add your key to the agent
ssh-add ~/.ssh/id_ed25519

Managing SSH Keys

Viewing Your Keys

Navigate to the cloud dashboard → SSH Keys to see all uploaded keys with their:

• Name
• Fingerprint
• Date added

Deleting a Key

1. Navigate to SSH Keys
2. Click Delete on the key you want to remove
3. Confirm the deletion

Adding Keys to Existing Instances

If you need to add an SSH key to an instance that is already running:

# From a machine that already has access
ssh root@your-instance-ip

# Add the new public key
echo "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAI... user@machine" >> ~/.ssh/authorized_keys

Or copy it directly from your local machine:

ssh-copy-id -i ~/.ssh/id_ed25519.pub root@your-instance-ip

Best Practices

1. Use Ed25519 keys — Shorter, faster, and more secure than RSA.
2. Set a passphrase — Protects your private key if your machine is compromised.
3. Use ssh-agent — Avoid typing your passphrase repeatedly.
4. One key per machine — Generate a unique key for each device. If a device is lost, revoke only that key.
5. Name keys descriptively — Use names like work-macbook, ci-server, or home-desktop so you can identify them later.
6. Audit regularly — Review your uploaded keys and remove any that are no longer in use.
7. Never share private keys — If multiple people need access, each person should upload their own public key.

Troubleshooting

Permission Denied (publickey)

ssh -v root@your-instance-ip

Common causes:

• Wrong key — Ensure the correct public key was selected during instance creation
• File permissions — Private key must be readable only by you: chmod 600 ~/.ssh/id_ed25519
• SSH agent — If using an agent, verify the key is loaded: ssh-add -l

Fix Permissions

chmod 700 ~/.ssh
chmod 600 ~/.ssh/id_ed25519
chmod 644 ~/.ssh/id_ed25519.pub

Next Steps

• Deploy a Cloud Compute instance with your SSH key
• Configure Networking with firewalls to restrict SSH access
• Review Images & Templates for available operating systems
• Learn about Security & Compliance for data protection