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

Step 1: Go to the terminal and type in the following command to edit system's /etc/rc.local file:

gksudo gedit /etc/rc.local

Step 2: Add the following line before the exit 0 line:

rfkill block bluetooth

Note: These instructions are for users who want to disable Bluetooth at boot by default in a way that it can easily be enabled afterward.

Gnome (Ubuntu 18.04+)

Disable Bluetooth by default

In Gnome, Bluetooth is managed by gnome-bluetooth, which should remember the last setting you used. But you can force it to always be disabled at boot like this:

echo "rfkill block bluetooth" >> ~/.profile

(Replace ~/.profile with ~/.zprofile if you're using zsh)

This avoids having to edit any system files such as /etc/rc.local

Manually enable Bluetooth

Whenever you're ready to turn it on click in the top-right > Settings > Bluetooth > click the switch near the top right

Or using the command line:

rfkill unblock bluetooth

Unity/Xfce (Ubuntu < 18.04, Xubuntu)

Disable Bluetooth by default

If you're using the Bluetooth applet in the top panel (blueman-applet), it has its own setting that will automatically turn Bluetooth on even if you've disabled it in other places (like /etc/bluetooth/main.conf or /etc/default/tlp).

To prevent Bluetooth from turning on at startup using the command line:

gsettings set org.blueman.plugins.powermanager auto-power-on false

Or through the GUI:

1. Click the Bluetooth applet > Plugins > PowerManager > Configuration
2. Uncheck Auto power-on

Next time you reboot, the Bluetooth applet will still be visible but Bluetooth will be off.

Manually enable Bluetooth

Click the Bluetooth applet > Turn Bluetooth On

1. block bluetooth in rc.local

Add this line at the end of the file /etc/rc.local right before the line exit 0:

rfkill block bluetooth

This will do the trick, but only in older Ubuntu versions using upstart.

2. reenable rc.local on systemd

On Ubuntu 15.10 with systemd as startup manager the /etc/rc.local file is not used by default any more, so call this on a terminal:

sudo systemctl edit --full rc-local

Which opens an editor. At the end of the file i added:

[Install]
WantedBy=multi-user.target

Those changes are activated by

sudo systemctl reenable rc-local

Now the file /etc/rc.local is used as you know it.

3. disable blueman-applet on start

sudo sed -i 's/NoDisplay=true/NoDisplay=false/g' /etc/xdg/autostart/blueman.desktop
gnome-session-properties

Now blueman-applet is visible and you can disable it from startup programs

4. Reboot to see the effect

I found another answer using tlp that works great for me with Ubuntu 18.04. Probably first tlp must be installed with

sudo apt install tlp

Then the file

/etc/default/tlp

contains some settings about devices like wifi and bluetooth. There is the key

RESTORE_DEVICE_STATE_ON_STARTUP

which is by default set to 0. After I switched it to 1 my last setting is remembered on the next boot. That means when I disable bluetooth in the top panel it stays disabled and when I enable bluetooth it stays enabled. Also there is the key

DEVICES_TO_DISABLE_ON_STARTUP

which can be set to

DEVICES_TO_DISABLE_ON_STARTUP="bluetooth"

Now bluetooth will be disabled on each boot. After changing this configuration bluetooth will can be enabled and disabled through menu and panel item. I think it's better than removing it from kernel modules.

Type the following into a terminal:

sudo gedit /etc/modprobe.d/blacklist.conf

At the bottom of the file, add the line:

blacklist bluetooth

Save the file and restart - Bluetooth should now be disabled.

You can change the services started at boot with the help of BUM.

Install it: sudo apt-get install bum

Run: sudo bum

Uncheck the box and click Apply.