Generating/Uploading a Custom SSH Key for Instances

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Secure Shell (SSH) keys offer a robust mechanism for authenticating remote access to your Compute Engine instances. Instead of relying on traditional passwords, SSH keys employ a pair of cryptographic keys: a private key (stored securely on your local machine) and a public key (uploaded to your instance).

To ensure seamless and secure connections, let’s walk through the steps of generating and uploading a custom SSH key:

  1. Key Generation (Local Machine):
  • Open your terminal or command prompt.
  • Use the ssh-keygen command:
ssh-keygen -t rsa -b 4096 -C "[email protected]"
  • You’ll be prompted for a file to save the key. If you don’t specify a name, the default is typically ~/.ssh/id_rsa (private key) and ~/.ssh/id_rsa.pub (public key).
  • Optionally, you can set a passphrase for added security.
  1. Upload Public Key (Google Cloud Console):
  • Navigate to the Compute Engine > Metadata section.
  • Click SSH Keys > Edit.
  • Click Add Item.
  • Open your public key file (usually with the .pub extension) in a text editor.
  • Copy the entire contents of the file, including the “ssh-rsa” prefix and your email comment at the end.
  • Paste the key into the text box on the GCP console.
  • Click Save.
  1. Connect via SSH:
  • From your terminal, you can now connect to your instance using the following command, replacing [USERNAME] with your username and [EXTERNAL_IP] with the external IP of your instance:
ssh [USERNAME]@[EXTERNAL_IP]
  • If you set a passphrase during key generation, you’ll be prompted to enter it.

Best Practices

  • Safeguard your private key. It’s the equivalent of a password and should never be shared.
  • If you lose your private key, you’ll lose access to any instances associated with it.
  • For multiple users, each should have their own unique SSH key pair.
  • Regularly review and rotate your SSH keys for enhanced security.

By diligently following these steps and adhering to best practices, you’ll fortify your Compute Engine instances with robust SSH key authentication, ensuring a secure and efficient workflow.

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