To automatically authenticate Tailscale on startup in Ubuntu, follow these steps:
- 
Generate a reusable auth key from the Tailscale admin console at https://login.tailscale.com/admin/authkeys. Make sure to select the appropriate options for your use case (e.g., whether the node is ephemeral or not). 
- 
On your Ubuntu machine, run the following commands to set up the auth key and create a systemd service: 
# Create a directory for the auth key