Bluetooth Pairing on Dual Boot of Windows & Linux Mint/Ubuntu - Stop having to Pair Devices

Question

When dual-booting Windows 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
• Ubuntu 20.04
• Ubuntu 22.10
• Linux Mint 17.X
• Linux Mint 18.X
• Linux Mint 21.X
• Fedora 25

On the Windows side, this works with 7, 10, and 11.

Answer 1

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). You need psexec as normal regedit doesn't have enough permissions to show this values.

     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). Note: on newer versions of windows the route to the device's properties is to go through Settings -> Bluetooth & devices -> Devices -> More devices and printer settings
     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. Note: If there are no keys visible after pairing, you likely need to add permissions to read (right click -> permissions) Keys\
     8. For convenience export it as a text file. click file -> export -> as text and save it to a shared partition/cloud.

   • Use chntpw from your Linux distro (easier). Start in a terminal then:

     1. sudo apt-get install chntpw

     2. Mount your Windows system drive in read-write mode

        • To find the drive use sudo lsblk -o NAME,FSTYPE,SIZE,MOUNTPOINT,LABEL. Depending on how your dual boot is setup its usually the first ntfs partition on the drive with /boot/efi. Note the NAME.
        • sudo mkdir /mnt/c
        • sudo mount --read-only /dev/<NAME> /mnt/c
        • To safely unmount the drive sudo umount /mnt/c
          • If you need to try a different drive or when finished all these instructions

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

        • on Windows 10 the root folder is "Windows", on Windows 7 it is "WINDOWS"

     4. chntpw -e SYSTEM opens a console

     5. Run these commands in that console:

        > # If there is no ControlSet001, then try CurrentControlSet
        > # on Windows 7, "services" below is lowercased.
        > cd ControlSet001\Services\BTHPORT\Parameters\Keys
        > ls
        # shows you your Bluetooth port's MAC address
        Node has 1 subkeys and 0 values
          key name
          <aa1122334455>
        > 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>
        > # Get the value of the REG_BINARY entry
        > 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) and later you may have to do this:

     1. Switch to root: sudo -i (In old versions of Ubuntu, '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:

        [LinkKey]
        Key=B99999999FFFFFFFFF999999999FFFFF
        

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!

Answer 2

Firstly, many answers advise replacing the key in [linkKey] section of the /var/lib/bluetooth/<ADAPTOR_MAC_ADDRESS>/<DEVICE_MAC_ADDRESS>/info file. This section now seems to be called [LongTermKey]. Also, [LocalSignatureKey] seems to now be [IdentityResolvingKey]. Some answers only mention changing the key in [linkKey], but you also need Enc,Ediv and Rand entries and the key for [IdentityResolvingKey].

Secondly, the device mac address may not be constant. In the case of my Logitech G604 it increments by one each time I pair. I updated these scripts here to resolve this.

Instructions

1. Boot into Linux and pair bluetooth device(s). You'll need the newly generated info and attributes files in /var/lib/bluetooth/<ADAPTOR_MAC_ADDRESS>/<DEVICE_MAC_ADDRESS>/.
2. Reboot into Windows and pair bluetooth device(s).
3. Download PSExec and run the following command from a Command Prompt running in Administator mode:

PsExec64.exe -s -i regedit /e C:\BTKeys.reg HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\BTHPORT\Parameters\Keys

4. Copy the C:\BTKeys.reg file to a USB key (or leave on C: drive if it's accessible from the Linux OS).
5. Turn off bluetooth device(s) and boot back into Linux. Don't pair the device again in Linux. It might generate a new mac address, which will break the Windows pairing. (I don't know if this is normal, but it's what happens with my Logitech G604).
6. Copy the BTKeys.reg file to your Linux filesystem.
7. Run clean_reg_file.py --file_path BTKeys.reg --output clean.reg to clean the file (converts encoding to UTF8 and strips quotation marks).
8. Run bluetooth_fix.py --reg_path clean.reg.
9. From a terminal with sudo, navigate to /var/lib/bluetooth/<ADAPTOR_MAC_ADDRESS>/.
10. Make a new directory corresponding to the device mac address from BTKeys.reg.
11. Copy info and attributes from the old mac address directory to the new one.
12. Open /var/lib/bluetooth/<ADAPTOR_MAC>/<NEW_DEVICE_MAC>/info and modify the values as per output from step 8.
13. Restart bluetooth with sudo systemctl restart bluetooth.