When dual booting Windows 7/10 and Linux Mint/Ubuntu, you may find yourself having to re-pair your Bluetooth devices again and again. This will happen every time you switch OS.

Now, how do you prevent this?

I'm answering my own question with the following guide, which has been tested on Ubuntu 14.4 and Linux Mint 17.2, 17.3 and now Linux Mint 18.x.


Why does this happen?

Basically, when you pair your device, your Bluetooth service generates a unique set of pairing keys. First, your computer stores the Bluetooth device's MAC address and pairing key. Second, your Bluetooth device stores your computer's MAC address and the matching key. This usually works fine, but the MAC address for your Bluetooth port will be the same on both Linux and Windows (it is set on the hardware level). Thus, when you re-pair the device in Windows or Linux and it generates a new key, that key overwrites the previously stored key on the Bluetooth device. Windows overwrites the Linux key and vice versa.

Bluetooth LE Devices: These may pair differently. I haven't investigated myself, but this may help Dual Boot Bluetooth LE (low energy) device pairing

How to fix

Using the instructions below, we'll first pair your Bluetooth devices with Ubuntu/Linux Mint, and then we'll pair Windows. Then we'll go back into our Linux system and copy the Windows-generated pairing key(s) into our Linux system.

  1. Pair all devices w/ Mint/Ubuntu
  2. Pair all devices w/ Windows
  3. Copy your Windows pairing keys in one of two ways:
    • Use psexec -s -i regedit.exe from Windows (harder)

      1. Go to "Device & Printers" in Control Panel and go to your Bluetooth device's properties. Then, in the Bluetooth section, you can find the unique identifier. Copy that (you will need it later).
      2. Download PsExec from http://technet.microsoft.com/en-us/sysinternals/bb897553.aspx.
      3. Unzip the zip you downloaded and open a cmd window with elevated privileges. (Click the Start menu, search for cmd, then right-click the CMD and click "Run as Administrator".)
      4. cd into the folder where you unzipped your download.
      5. Run psexec -s -i regedit.exe
      6. Navigate to find the keys at HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\BTHPORT\Parameters\Keys.  If there is no CurrentControlSet, try ControlSet001.
      7. You should see a few keys labels with the MAC addresses - write down the MAC address associated with the unique identifier you copied before.
    • Use chntpw from your Linux distro (easier). Start in a terminal then:

      1. sudo apt-get install chntpw

      2. Mount your Windows system drive

      3. cd /[WindowsSystemDrive]/Windows/System32/config

      4. chntpw -e SYSTEM opens a console

      5. Run these commands in that console:

        > cd CurrentControlSet\Services\BTHPORT\Parameters\Keys
        > # if there is no CurrentControlSet, then try ControlSet001
        > # on Windows 7, "services" above is lowercased.
        > ls
        # shows you your Bluetooth port's MAC address
        Node has 1 subkeys and 0 values
          key name
        > cd aa1122334455  # cd into the folder
        > ls  
        # lists the existing devices' MAC addresses
        Node has 0 subkeys and 1 values
          size     type            value name             [value if type DWORD]
            16  REG_BINARY        <001f20eb4c9a>
        > hex 001f20eb4c9a
        => :00000 XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX ...ignore..chars..
        # ^ the XXs are the pairing key
      6. Make a note of which Bluetooth device MAC address matches which pairing key. The Mint/Ubuntu one won't need the spaces in-between.  Ignore the :00000.

  4. Go back to Linux (if not in Linux) and add our Windows key to our Linux config entries. Just note that the Bluetooth port's MAC address is formatted differently when moving from Windows to Linux - referenced as aa1122334455 in Windows in my example above. The Linux version will be in all caps and punctuated by ':' after every two characters - for example AA:11:22:33:44:55.  Based on your version of Linux, you can do one of these:
    • Before Mint 18/16.04 you could do this:
      1. sudo edit /var/lib/bluetooth/[MAC address of Bluetooth]/linkkeys - [the MAC address of Bluetooth] should be the only folder in that Bluetooth folder.

      2. This file should look something like this:

        [Bluetooth MAC]   [Pairing key]                 [digits in pin]  [0]
        AA:11:22:33:44:55 XXXXXXXXxxXXxXxXXXXXXxxXXXXXxXxX 5 0
        00:1D:D8:3A:33:83 XXXXXXXXxxXXxXxXXXXXXxxXXXXXxXxX 4 0
      3. Change the Linux pairing key to the Windows one, minus the spaces.

    • In Mint 18 (and Ubuntu 16.04) you may have to do this:
      1. Switch to root: su -

      2. cd to your Bluetooth config location /var/lib/bluetooth/[bth port MAC addresses]

      3. Here you'll find folders for each device you've paired with. The folder names being the Bluetooth devices' MAC addresses and contain a single file info. In these files, you'll see the link key you need to replace with your Windows ones, like so:

  5. Once updated, restart your Bluetooth service in one of the following ways, and then it works!
    • Ubuntu, Mint, Arch:

      sudo systemctl restart Bluetooth 
    • Alternatively, reboot your machine into Linux.

  6. Reboot into Windows - it works!
  • 4
    I came here having just installed Ubuntu 16.04LTS (dualboot with Windows) and having already paired my keyboard and mouse with it. Instead of copying the key from Windows to Ubuntu, I did it in reverse using chntpw: After mounting your windows partition and doing all the chntpw stuff @Mario Flores did, do ed "value name" in the chntpw terminal. Take the "Key=" in your bluetooth device's info file on Ubuntu and enter it like this in chntpw: ": XX XX XX XX XX ...." where XX is every 2 letters/numbers in the key. Then type s and it will be saved to the registry. Repeat if needed. – Sameer Puri Sep 17 '16 at 3:07
  • 3
    should it be: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\BTHPORT\Parameters (so HLKM) – TiloBunt Sep 18 '16 at 0:44
  • 5
    By the way, if you've got a Bluetooth LE device, there will be a few more things to do and unix.stackexchange.com/questions/402488 may help you. – Frederick Zhang May 20 '18 at 11:39
  • 4
    In Windows 10, you'll find your keys at "Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\BTHPORT\Parameters\Keys". – Thomas Aug 16 '18 at 22:27
  • 14
    Note, if you're doing it from Linux, but target recent Windows 10, the correct path is \ControlSet001\Services\BTHPORT\Parameters\Keys. – Dalibor Karlović Aug 2 '19 at 8:48

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