The Persistent Radio
Ubuntu Linux is designed to be ready for modern peripherals immediately upon booting. Because so many users rely on wireless mice, keyboards, and headphones, the operating system’s Bluetooth service (`bluetoothd`) is configured to start automatically the moment you turn on your computer. Furthermore, it automatically powers on the physical Bluetooth radio hardware. If you rarely use Bluetooth devices, this default behavior is a persistent drain on your laptop’s battery. Even worse, if you manually turn Bluetooth off via the top-right system menu, Ubuntu will frustratingly turn it right back on the very next time you reboot the machine.
Disabling the Boot Service
To keep the radio permanently powered down and stop Ubuntu from automatically turning on Bluetooth on every startup, you must modify the underlying system service configuration.
You cannot permanently disable this via the graphical settings; you must use the terminal to stop the service from launching at boot. Open your terminal by pressing Ctrl+Alt+T. To prevent the Bluetooth service from starting automatically when the computer turns on, type exactly: sudo systemctl disable bluetooth.service and press Enter (provide your password). To ensure no other program can accidentally wake it up, you can also mask the service by typing: sudo systemctl mask bluetooth.service. The next time you restart your computer, the Bluetooth radio will remain completely powered off. If you ever need to use a wireless device in the future, you will have to open the terminal and type sudo systemctl unmask bluetooth.service followed by sudo systemctl start bluetooth.service to manually turn it back on.