Fixing Bluetooth Dual Boot on EndeavourOS and Windows

If you dual boot Linux and Windows and share Bluetooth devices between them, you’ve probably hit this annoying issue: the speakers connect fine on one OS, and then after switching, they refuse to pair on the other.

When you pair a Bluetooth device, a link key is generated and stored on both the host and the device. The problem is that both Windows and Linux see the same physical Bluetooth adapter — same MAC address — but they don’t share their key stores. So when you pair on Linux, it writes a new key to the device. Boot into Windows, and Windows has a stale key that no longer matches. Pair on Windows, and now Linux is the one with the stale key.

The fix is simple in principle: get both OSes using the same key. The easiest way to do that is to pair on Windows, extract the key Windows stored, and copy it into Linux’s Bluetooth config.

Why This Is Super Annoying

The Bluetooth link keys in Windows are stored in the registry under:

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HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\BTHPORT\Parameters\Keys

But they’re locked to the SYSTEM account. Even opening regedit as Administrator won’t show them — you get an empty folder. This catches a lot of people out.

How To Fix

Step 1: Pair on Windows

Make sure your device is paired and connected in Windows first. Go to Settings → Bluetooth & devices and confirm it’s there.

Step 2: Get PsExec

Download PsTools from Microsoft Sysinternals and extract PsExec.exe into C:\Windows\System32.

Step 3: Open Regedit as SYSTEM

Open Command Prompt as Administrator and run:

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psexec -s -i regedit.exe

This launches regedit under the SYSTEM account, which is the only account that can actually read the Bluetooth key store.

Step 4: Find the Key

Navigate to:

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HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\BTHPORT\Parameters\Keys

Expand the folder — you should now see a subfolder named after your Bluetooth adapter’s MAC address. Inside that, either a value named after your device’s MAC (for classic BR/EDR devices) or a subfolder for BLE devices.

In my case, the device (a Bose Mini II SoundLink) was a classic BR/EDR device. The link key was stored as a REG_BINARY value named with the device MAC, directly under the adapter MAC folder:

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Keys\<adapter_mac>\<device_mac> = xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx

Note down the full hex value.

Step 5: Update Linux

Boot into Linux. Find the info file for the device:

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sudo ls /var/lib/bluetooth/

This shows your adapter MAC. Then:

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sudo ls /var/lib/bluetooth/<ADAPTER_MAC>/

This shows paired device directories. Find the one for your device (the MAC may differ slightly from Windows — Linux uses uppercase with colons).

Open the info file:

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sudo nano /var/lib/bluetooth/<ADAPTER_MAC>/<DEVICE_MAC>/info

Find the [LinkKey] section and replace the Key= value with the Windows key, formatted as uppercase hex with no spaces or separators:

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[LinkKey]
Key=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Type=4
PINLength=0

Save and restart Bluetooth:

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sudo systemctl restart bluetooth

Your device should now connect without re-pairing.

Notes

If you re-pair the device on either OS at any point, the key changes and you’ll need to redo this.
BLE devices store keys differently — look for a [LongTermKey] section instead of [LinkKey], with LTK, ERand, and EDIV values.
The device MAC in Linux may not match the one shown in Windows exactly. Check sudo ls /var/lib/bluetooth/<adapter>/ to find the right directory.