How can I deactivate Bluetooth on system startup?

For Ubuntu 20.10

For this ubuntu edit /etc/bluetooth/main.conf and find the line

AutoEnable=true

and replace it with:

AutoEnable=false

18.04+

18.04* users who don't naturally have a /etc/rc.local, you'll need to create one and make it executable. To make things slightly easier, you can just paste the following command into a terminal:

sudo install -b -m 755 /dev/stdin /etc/rc.local << EOF
#!/bin/sh
rfkill block bluetooth
exit 0
EOF

Run sudoedit /etc/rc.local and add this before line with exit 0:

rfkill block bluetooth

You should still be able to enable Bluetooth through the top bar applet.

This should work for most systems but it looks like there are a few bugs lurking in the kernel's ACPI for Thinkpads. If you're on a Thinkpad, add the following to /etc/rc.local:

echo disable > /proc/acpi/ibm/bluetooth

Or check out ibm-acpi - IBM ThinkPad ACPI Extras Driver -- some reports suggest that ibm-acpi includes bluetooth control (amongst other nice things). But I don't have the hardware so I'm completely unable to verify these claims. Good luck.

I found a how-to with a clean "workaround" here (archive link for posterity)

Actually changing /etc/bluetooth/main.conf was enough for me.

Search for the entry:

AutoEnable=true

and change the value to:

AutoEnable=false

It was enough for me, although the article describes some other steps that may or may not be necessary.

On Ubuntu 17.04 and older the option was named InitiallyPowered.

16.04+

From ubuntu 16.04 onwards systemd manages startup services like bluetooth ... to view current status issue following in a terminal

sudo systemctl status bluetooth.service 

to deactivate bluetooth on startup issue this

sudo systemctl disable bluetooth.service

then on next reboot bluetooth will not be active ... to enable bluetooth issue ( then reboot )

sudo systemctl enable bluetooth.service

To disable the bluetooth driver from loading on startup:

sudo $EDITOR /etc/modprobe.d/blacklist.conf

add:

blacklist btusb

Enabling it later should just be:

sudo modprobe btusb