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# Bluetooth

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Related articles

- Bluetooth mouse
- Bluetooth keyboard
- Bluetooth headset
- Blueman
- ObexFTP

Bluetooth is a standard for the short-range wireless interconnection of cellular phones, computers, and other electronic devices. In Linux, the canonical implementation of the Bluetooth protocol stack is BlueZ.

## Installation

1. Install the bluez package, providing the Bluetooth protocol stack.
2. Install the bluez-utils package, providing the `bluetoothctl` utility. Alternatively install bluez-deprecated-tools to additionally have the deprecated BlueZ tools.
3. The generic Bluetooth driver is the `btusb` kernel module. Check whether that module is loaded. If it is not, then load the module.
4. Start/enable `bluetooth.service`.

Note:

- By default the Bluetooth daemon will only give out bnep0 devices to users that are a member of the `lp` group. Make sure to add your user to that group if you intend to connect to a Bluetooth tether. You can change the group that is required in the file `/usr/share/dbus-1/system.d/bluetooth.conf`.
- Some Bluetooth adapters are bundled with a Wi-Fi card (e.g. older Intel Centrino cards). These require that the Wi-Fi card is firstly enabled (typically a keyboard shortcut on a laptop) in order to make the Bluetooth adapter visible to the kernel.
- Some Bluetooth cards (e.g. Broadcom) conflict with the network adapter. Thus, you need to make sure that your Bluetooth device gets connected before the network service boot.
- Some tools such as hcitool and hciconfig have been deprecated upstream, and are no longer included in bluez-utils. Since these tools will no longer be updated, it is recommended that scripts be updated to avoid using them. If you still desire to use them, install bluez-deprecated-tools. See FS#53110 and the Bluez mailing list for more information.
- Since this commit, bluez-obex and bluez-mesh have been separated from bluez. Therefore, if you plan to transfer files over Bluetooth, bluez-obex needs to be installed.

### Front-ends

#### Console

- bluetoothctl — Pairing a device from the shell is one of the simplest and most reliable options.

  https://www.bluez.org/ || bluez-utils

- bluetuith — Provides a bluetooth manager via a Terminal User Interface for easier pairing and device/adapter management, with OBEX File Transfer and mouse support.

  https://www.github.com/darkhz/bluetuith || bluetuithAUR

- bluetui — TUI for managing bluetooth devices.

  https://github.com/pythops/bluetui || bluetuiAUR

Tip: To automate bluetoothctl commands, use `echo -e "command1\ncommand2\n" | bluetoothctl` or `bluetoothctl -- command`.

#### Graphical

This article or section needs language, wiki syntax or style improvements. See Help:Style for reference.

Reason: Abuses Template:App. (Discuss in Talk:Bluetooth)

The following packages allow for a graphical interface to customize Bluetooth.

- GNOME Bluetooth — GNOME's Bluetooth tool.
  - gnome-bluetooth-3.0 provides the back-end (gnome-bluetooth is now legacy)
  - gnome-shell provides the status monitor applet
  - gnome-control-center provides the configuration front-end GUI that can be accessed by typing Bluetooth on the Activities overview, or with the `gnome-control-center bluetooth` command.
  - You can also launch the `bluetooth-sendto` command directly to send files to a remote device.
  - nautilus-bluetoothAUR adds a "Send via Bluetooth" entry to Nautilus' right-click menu
  - To receive files, open the Bluetooth settings panel; you can only receive whilst the Bluetooth panel is open.
  - To add a Bluetooth entry to the Send To menu in Thunar's file properties menu, see instructions here. (The command that needs to be configured is `bluetooth-sendto %F`).

  https://wiki.gnome.org/Projects/GnomeBluetooth ||

- Bluedevil — KDE's Bluetooth tool. If there is no Bluetooth icon visible in Dolphin and in the system tray, enable it in the system tray options or add a widget. You can configure Bluedevil and detect Bluetooth devices by clicking the icon. An interface is also available from the KDE System Settings.

  https://invent.kde.org/plasma/bluedevil || bluedevil

- Blueberry — Linux Mint's spin-off of GNOME Bluetooth, which works in all desktop environments. Blueberry does not support receiving files through Obex Object Push.

  https://github.com/linuxmint/blueberry || blueberry

- Blueman — A full featured Bluetooth manager.

  https://github.com/blueman-project/blueman || blueman

- ObexFTP — A tool for transferring files to/from any OBEX enabled device.

  http://dev.zuckschwerdt.org/openobex/wiki/ObexFtp || obexftpAUR

- Overskride — A simple yet powerful bluetooth client.

  https://github.com/kaii-lb/overskride#overskride || overskrideAUR

## Pairing

Note: Before using the Bluetooth device, make sure that it is not blocked by rfkill.

This section describes directly configuring bluez5 via the bluetoothctl CLI, which might not be necessary if you are using an alternative front-end tool (such as GNOME Bluetooth).

The exact procedure depends on the devices involved and their input functionality. What follows is a general outline of pairing a device using `bluetoothctl`.

Start the `bluetoothctl` interactive command. Input `help` to get a list of available commands.

1. (optional) Select a default controller with `select MAC_address`.
2. (optional) Enter `power on` to turn the power to the controller on if the device is set to off. It is on by default; see #Default adapter power state.
3. Enter `devices` to get the MAC address of the device with which to pair.
4. Enter device discovery mode with `scan on` command if device is not yet on the list.
5. Turn the agent on with `agent on` or choose a specific agent: if you press tab twice after `agent` you should see a list of available agents. A bluetooth agent is what manages the Bluetooth 'pairing code'. It can either respond to a 'pairing code' coming in, or can send one out. The `default-agent` should be appropriate in most cases.[1]
6. Enter `pair MAC_address` to do the pairing (tab completion works).
7. If using a device without a PIN, one may need to manually trust the device before it can reconnect successfully. Enter `trust MAC_address` to do so.
8. Enter `connect MAC_address` to establish a connection.

An example session may look this way:

    $ bluetoothctl

    [NEW] Controller 00:10:20:30:40:50 hostname [default]
    [bluetooth]# agent KeyboardOnly
    Agent registered

    [bluetooth]# default-agent
    Default agent request successful

    [bluetooth]# power on
    Changing power on succeeded
    [CHG] Controller 00:10:20:30:40:50 Powered: yes

    [bluetooth]# scan on
    Discovery started
    [CHG] Controller 00:10:20:30:40:50 Discovering: yes
    [NEW] Device 00:12:34:56:78:90 device name
    [CHG] Device 00:12:34:56:78:90 LegacyPairing: yes

    [bluetooth]# pair 00:12:34:56:78:90
    Attempting to pair with 00:12:34:56:78:90
    [CHG] Device 00:12:34:56:78:90 Connected: yes
    [CHG] Device 00:12:34:56:78:90 Connected: no
    [CHG] Device 00:12:34:56:78:90 Connected: yes
    Request PIN code
    [agent] Enter PIN code: 1234
    [CHG] Device 00:12:34:56:78:90 Paired: yes
    Pairing successful
    [CHG] Device 00:12:34:56:78:90 Connected: no

    [bluetooth]# connect 00:12:34:56:78:90
    Attempting to connect to 00:12:34:56:78:90
    [CHG] Device 00:12:34:56:78:90 Connected: yes
    Connection successful

### Dual boot pairing

To pair devices on dual boot setups you need to change the pairing keys on your Linux install so that they are consistent with what Windows or macOS is using.

This page only describes the manual method of doing so. To automate the process, see the bt-dualboot project and the related repositories.

#### Setup

To do this, first pair your device on your Arch Linux install. Then reboot into the other OS and pair the device. Now you need to extract the pairing keys, but first switch off the Bluetooth devices to prevent any connection attempts.

Note: Some Logitech devices, such as the Logitech MX Master and Logitech 604 Lightspeed, increment the MAC address by one every time that the device is paired with a new system. You should determine whether this is the case, so that it can be accounted for at the end of the process.

#### For Windows

##### Extracting on Windows

First, boot into Windows.

The registry key containing the link keys may only be accessed by the SYSTEM account, which cannot be logged into. Therefore, you will need Microsoft's PsExec tool from the official Windows Sysinternals site in order to run `regedit.exe` as `SYSTEM`.

Download PsTools, and extract `PsExec64.exe`.

In an administrator instance of a command shell, from the location of the extracted EXE, launch the registry editor:

    .\PsExec64.exe -s -i regedit.exe

In the registry editor, navigate to the following registry key:

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

Within this registry key is one subkey per Bluetooth adapter, named by MAC address. If there are multiple subkeys, and you are unsure of which to use, follow this guide to find the MAC address for the desired Bluetooth adapter.

In the desired adapter's registry key, there is a name-value pair for each paired device, with the name being its MAC address. Additionally, you might see some subkeys named by MAC addresses, each containing name-value pairs with names like `LTK` or `IRK`. These subkeys (if any) are for Bluetooth 5.1 devices. If the device you're trying to share has a subkey, it is a Bluetooth 5.1 device. If it does not have a subkey, only a name-value pair, it is not a Bluetooth 5.1 device.

Right click on the adapter's registry key and export it as a .reg file. This is a text file that you can copy keys from. As mentioned, it contains pairing keys in name-value pairs for non-Bluetooth 5.1 devices, and pairing keys (and some other information) in per-device subkeys for Bluetooth 5.1 devices. Make this file available to your Linux installation and reboot into it.

If the device you want to share is not a Bluetooth 5.1 device, jump to #Saving the configuration. If it is a Bluetooth 5.1 device, you need to make some modifications to the pairing keys and the associated information before finishing up. Refer to #Preparing Bluetooth 5.1 Keys to see how.

##### Extracting on Linux

Note: If your Windows partition is encrypted with Bitlocker, you will not be able to access it from Linux using chntpw.

Reboot into Arch. Install chntpw. Mount your windows system drive.

    $ cd /path/to/windows/system/Windows/System32/config
    $ chntpw -e SYSTEM

Inside the `chntpw` environment, run

    > cd CurrentControlSet\Services\BTHPORT\Parameters\Keys

Instead of `CurrentControlSet`, you may see `ControlSet00X` (check using ls):

    > cd ControlSet00X\Services\BTHPORT\Parameters\Keys

Then get your Bluetooth adapter's MAC address and enter its folder

    > ls
    > cd your-device's-mac-address

Do the same for your paired devices. If this is not a Bluetooth 5.1 device, you will only see the pairing key:

    > ls

    Node has 0 subkeys and 1 values
    size  type        value name    [value if type DWORD]
    16    REG_BINARY <123456789876>

If so, get your device's key through `hex`:

    > hex 123456789876

    :00000 XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX (some other chars)

The "XX"s are the pairing key. Make note of which keys map to which MAC addresses.

If this is a Bluetooth 5.1 device, then you will see several keys corresponding to the one device.

    Node has 0 subkeys and 8 values
      size     type              value name             [value if type DWORD]
        16  3 REG_BINARY         <LTK>
         4  4 REG_DWORD          <KeyLength>               16 [0x10]
         8  b REG_QWORD          <ERand>
         4  4 REG_DWORD          <EDIV>                 37520 [0x9290]
        16  3 REG_BINARY         <IRK>
         8  b REG_QWORD          <Address>
         4  4 REG_DWORD          <AddressType>              1 [0x1]
         4  4 REG_DWORD          <AuthReq>                 45 [0x2d]

Refer to #Preparing Bluetooth 5.1 Keys to see how to use these, using `hex value_name` to obtain the requested values.

Finally, to import the key(s) into your Linux installation, proceed to #Saving the configuration.

#### For macOS

Boot into macOS:

- For macOS Monterey or newer:
  1. Open Keychain Access and search for Bluetooth.
  2. Sort by date.
  3. If you've recently removed and reconnected the device then you can simply sort the keys by date modified and pick the latest. It is probably called MobileBluetooth (for older Bluetooth devices) or is just an UUID (for Bluetooth 5.1+).
  4. Double click on the entry. Check that the MAC address in the Account field matches the MAC address of your device.
  5. Click the "Show password" checkbox. You will now need to enter your password, twice.
  6. Copy the text in the password field, it's actually an XML file (`⌘+a` `⌘+c`)
  7. Paste the text in `bt_keys.txt` in your home directory.
- For High Sierra or newer, run the following in a terminal:

      # defaults read /private/var/root/Library/Preferences/com.apple.bluetoothd.plist LinkKeys > ~/bt_keys.txt

- For Sierra or older, run the following in a terminal:

      # defaults read /private/var/root/Library/Preferences/blued.plist LinkKeys > ~/bt_keys.txt

The `~/.bt_keys.txt` file now contains the established Bluetooth keys. For older versions of macOS (High Sierra and older) you will have to reverse the keys before proceeding. For example, `98 54 2f aa bb cc dd ee ff gg hh ii jj kk ll mm` becomes `MM LL KK JJ GG FF EE DD CC BB AA 2F 54 98`.

Note: The reversal can be done with the following Python code:

    >>> key = "98 54 2f aa bb cc dd ee ff gg hh ii jj kk ll mm"
    >>> " ".join(reversed(key.strip().split()))

If this is a Bluetooth 5.1 device, then there will be more than one key corresponding to one device. Refer to #Preparing Bluetooth 5.1 Keys to see how to use these.

Finally, to import the key(s) into your Linux installation, reboot into Linux and proceed to #Saving the configuration.

#### Preparing Bluetooth 5.1 Keys

This article or section needs expansion.

Reason: We are still working on getting a comprehensive idea of how these work across vendors. For now, documenting specific devices' compatibility with these methods is helpful - especially non-Logitech data points. (Discuss in Talk:Bluetooth#Bluetooth 5.1 Devices)

If you observed the presence of Bluetooth 5.1 keys while following #For Windows or #For macOS, you must apply certain transformations to their values before importing them into Linux. Create the requested files with their appropriate contents, for installation in #Saving the configuration. This process will depend on the device, and some of the values have to be manipulated; code utilities for doing so are provided below.

Device | Source Key and Transformations (Windows) | Source Key and Transformations (macOS) | Destination Key File
--- | --- | --- | ---
Logitech MX Master 3 Logitech MX Master 3S Logitech MX Keys Logitech MX Mechanical Xbox One S Wireless Controller | Copy `IRK`. Remove the spaces between the hex octets. | ? | `IdentityResolvingKey.Key`
Copy `LTK`. Remove the spaces between the hex octets. | ? | `SlaveLongTermKey.Key` and `PeripheralLongTermKey.Key`
`ERand` and `EDIV` should be `0` | Random Number and Encrypted Diversifier should be `0`. | –
Logitech MX Anywhere 2S | Copy `IRK`. Remove the spaces between the hex octets. | ? | `IdentityResolvingKey.Key`
Copy `CSRK`. Remove the spaces between the hex octets. | ? | `LocalSignatureKey.Key`
Copy `LTK`. Remove the spaces between the hex octets. | ? | `LongTermKey.Key`
Copy `KeyLength`. Convert the whole number to decimal. | ? | `LongTermKey.EncSize`
Copy `EDIV`. Convert the whole number to decimal. | ? | `LongTermKey.EDiv`
Copy `ERand`. Reverse the order of the octets. Convert the whole number to decimal. | ? | `LongTermKey.Rand`
ThinkPad TrackPoint Keyboard II Pebble M350 mouse Logitech G604 Lightspeed mouse | Copy `IRK`. Reverse the order of the octets. | Copy Remote IRK. Convert from base64 to hex. | `IdentityResolvingKey.Key`
Copy `LTK`. Remove the spaces between the hexadecimal octets. | Copy Remote Encryption > Long-term Key. Convert from base64 to hex. | `LongTermKey.Key`
Copy `ERand`. Reverse the order of the octets. Convert the whole number to decimal. | Copy Remote Encryption > Random Number. Convert from base64 to a little-endian decimal number (see Python code below). | `LongTermKey.Rand`
Copy `EDIV`. Reverse the order of the octets. Convert the whole number to decimal. | Copy Remote Encryption > Encrypted Diversifier. Convert from base64 to a little-endian decimal number (see Python code below). | `LongTermKey.EDiv`
Other devices | Copy `LTK`. Remove the spaces between the hex octets. | Copy Remote IRK. Convert from base64 to hex. | `LongTermKey.Key`
Copy `ERand`. Reverse the order of the octets. Convert the whole number to decimal. | Copy Remote Encryption > Long-term Key. Convert from base64 to hex. | `LongTermKey.Rand`
Copy `EDIV`. Remove the spaces between the hex octets. | Copy Remote Encryption > Encrypted Diversifier. Convert from base64 to hex. Reverse the order of the octets. | `LongTermKey.EDiv`
Xbox wireless controller | Copy `LTK`. Remove the spaces between the hex octets. | ? | `SlaveLongTermKey.Key`

Note:

- To just remove the spaces from a value, you can use this online tool or this Python code:

    >>> "key_value".replace(" ", "")

- This Python code does only the octet reversal:

    >>> ERand=" 63 02 84 B8 5D 40 44 DF   "
    >>> ERand=list(reversed(ERand.strip().split()))

- This Python code does the additional decimal conversion required for some:

    >>> int("".join(ERand), 16)
    16088054540146049635

- This Python code does the base64 to hex conversion:

    binascii.hexlify(base64.decodebytes(b'...')).upper()

- This Python code does the full macOS Encrypted Diversifier conversion:

    struct.unpack('<H', base64.decodebytes(b'...'))

- This Python code does the full macOS Random Number conversion:

    struct.unpack('<Q', base64.decodebytes(b'...'))

For an example of the general case:

- An `LTK` of `48 4D AF CD 0F 92 22 88 0A 52 9A F4 76 DA 8B 94` makes for a `LongTermKey.Key` of `484DAFCD0F9222880A529AF476DA8B94`.
- An `ERand` of `63 02 84 B8 5D 40 44 DF` makes for a `Rand` of `16088054540146049635`.
- An `EDIV` of `37520` makes for an `EDiv` of `37520`.

#### Saving the configuration

Now that you have the keys change user to root, then continue with:

    # cd /var/lib/bluetooth/BT-Adapter-MAC-address

Here you will find folders for each paired Bluetooth device. For each device you want to pair with Arch and your dual boot, do the following:

    # cd device-MAC-address

Note: At this point, if you are using a device which increments its MAC address on pairing, you must move the MAC address directory to the incremented path. Either copy the MAC address from Windows, or increment it yourself while minding the fact that each octet is a two-digit hexadecimal number.

If you have a pairing key (i.e. this is not a Bluetooth 5.1 device), then edit the `info` file and change the key under `[LinkKey]`. E.g.:

    info

    [LinkKey]
    Key=XXXXXXXXXXXXXXX

Note: You will have to make sure that all the letters are in capital case. Remove any spaces.

If you have several keys, as in Bluetooth 5.1, edit the `info` file and substitute all applicable keys with their recorded values. E.g. for an Xbox One S Wireless Controller:

    info

    [IdentityResolvingKey]
    Key=<IdentityResolvingKey.Key>

    [PeripheralLongTermKey]
    Key=<PeripheralLongTermKey.Key>

    [SlaveLongTermKey]
    Key=<SlaveLongTermKey.Key>

Then restart `bluetooth.service` and `pulseaudio` (with `pulseaudio -k && pulseaudio --start`).

You should be able to connect to your device now.

Note: Depending on your Bluetooth manager, you may need to perform a full reboot in order to reconnect to the device.

## Configuration

### Default adapter power state

As of bluez 5.65, BlueZ' default behavior is to power on all Bluetooth adapters when starting the service or resuming from suspend. [2]

If you would like the adapter to not be automatically enabled (e.g. on a portable device where you wish to save battery), set `AutoEnable=false` in `/etc/bluetooth/main.conf` in the `[Policy]` section:

    /etc/bluetooth/main.conf

    [Policy]
    AutoEnable=false

The adapter can still be turned on manually by running `power on` as described in #Pairing.

### Discoverable on startup

If the device should always be visible and directly connectable:

    /etc/bluetooth/main.conf

    [General]
    DiscoverableTimeout = 0

### Wake from suspend

To allow Bluetooth keyboards, mice, etc. to wake the system from suspend. First, check the bios settings and make sure that wake from USB is not disabled. In many cases, Bluetooth from the motherboard is a USB device.

Find the vendor code and device ID for the Bluetooth adapter.

    $ lsusb | grep bluetooth -i

    Bus 001 Device 002: ID 8087:0039 Intel Corp. AX200 Bluetooth

Add a new udev rule for the vendor code and device ID to enable wake from suspend.

    /etc/udev/rules.d/91-keyboard-mouse-wakeup.rules

    SUBSYSTEM=="usb", ATTRS{idVendor}=="8087", ATTRS{idProduct}=="0039" RUN+="/bin/sh -c 'echo enabled > /sys$env{DEVPATH}/../power/wakeup;'"

To automatically re-configure your Bluetooth keyboard after wakeups to e.g. have a different keymap or key press repeat rate (for details, see Xorg/Keyboard configuration#Adjusting typematic delay and rate and xmodmap), create an executable script.

    configure_keyboard.sh

    #!/bin/sh
    export DISPLAY=:0
    xset r rate 220 30
    xmodmap /your/path/to/.Xmodmap

Then create an additional udev rule like above.

    /etc/udev/rules.d/92-keyboard-reconfiguration-wakeup.rules

    SUBSYSTEM=="usb", ATTRS{idVendor}=="8087", ATTRS{idProduct}=="0039" RUN+="/your/path/to/configure_keyboard.sh"

### Enabling experimental features

The Bluez stack keeps new, potentially buggy features behind the D-Bus experimental and kernel experimental options. The functionality included under these varies over time, as experimental features are determined to be stable and no longer require the option (as an example: enabling D-Bus experimental interfaces currently allows to report battery level for old headsets). To enable these, uncomment the corresponding line in the configuration:

    /etc/bluetooth/main.conf

    ...

    # Enables D-Bus experimental interfaces
    # Possible values: true or false
    #Experimental = true

    # Enables kernel experimental features, alternatively a list of UUIDs
    # can be given.
    # Possible values: true,false,<UUID List>
    # Possible UUIDS:
    ...
    # Defaults to false.
    #KernelExperimental = true

Alternatively, you can edit the `bluetooth.service` to add the `--experimental` or `--kernel` flag, like this drop-in file:

    /etc/systemd/system/bluetooth.service.d/override.conf

    [Service]
    ExecStart=
    ExecStart=/usr/lib/bluetooth/bluetoothd --experimental

Either way, you must then restart the `bluetooth.service`.

## Audio

You will typically need to take an additional step to integrate the audio server with Bluetooth. This is detailed in the below sections.

See the Bluetooth headset page for more information about Bluetooth audio and Bluetooth headsets.

### PulseAudio

In order to be able to use audio equipment like Bluetooth headphones or speakers, you need to install the additional pulseaudio-bluetooth package. Make sure to restart pulseaudio to make the installation take effect: `pulseaudio -k`. With a default PulseAudio installation (specifically, using a user instance with the packaged `default.pa`) you should immediately be able to stream audio from a Bluetooth device to your speakers. [3]

If you have a system-wide PulseAudio setup make sure the user running the daemon (usually `pulse`) is in the `lp` group and you load the Bluetooth modules in your PulseAudio config:

    /etc/pulse/system.pa

    ...
    load-module module-bluetooth-policy
    load-module module-bluetooth-discover
    ...

Optionally, add `load-module module-switch-on-connect` if you want to auto-switch all audio to the Bluetooth device.

### PipeWire

PipeWire as of v0.3.19 enables its Bluetooth support by default.

### ALSA

Note: Bluez5 has dropped direct integration for ALSA and supports PulseAudio only. Follow the instructions below if you cannot or do not want to use PulseAudio.

First, ensure that your Bluetooth audio device is correctly paired and connected to the system.

Then, install bluez-alsa-gitAUR, start (and enable) the `bluealsa` service, and add your user to the `audio` group.

Run the following command to check if everything is working as intended (replace `XX:XX:XX:XX:XX:XX` and `FILE.wav` below):

    $ aplay -D bluealsa:SRV=org.bluealsa,DEV=XX:XX:XX:XX:XX:XX,PROFILE=a2dp FILE.wav

Finally, add the following lines to your `~/.asoundrc`:

    ~/.asoundrc

    defaults.bluealsa {
        service "org.bluealsa"
        device "XX:XX:XX:XX:XX:XX"
        profile "a2dp"
    }

You can now use the `bluealsa` device to reach your Bluetooth audio device. Volume management is conducted normally via `alsamixer` with the option `-D bluealsa`.

## Bluetooth serial

To get Bluetooth serial communication working on Bluetooth-to-Serial modules (HC-05, HC-06) do the following steps:

Pair your Bluetooth device using `bluetoothctl` as described above.

Install bluez-deprecated-tools, as it provides certain functionality which is missing from newer tools.

Bind paired device MAC address to tty terminal:

    # rfcomm bind rfcomm0 MAC_address_of_Bluetooth_device

Now you can open `/dev/rfcomm0` for serial communication:

    $ picocom /dev/rfcomm0 -b 115200

## Troubleshooting

This article or section is out of date.

Reason: Replace hciconfig with newer commands. (Discuss in Talk:Bluetooth)

### General Troubleshooting

#### Debugging

In order to debug, first stop `bluetooth.service`.

And then start it with the `-d` parameter:

    # /usr/lib/bluetooth/bluetoothd -n -d

Another option is via the `btmon` tool.

#### Deprecated BlueZ tools

Eight BlueZ tools were deprecated and removed from bluez-utils, although not all of them were superseded by newer tools. The bluez-deprecated-tools package provides an alternative version of bluez-utils with the deprecated tools.

Deprecated tool | Most likely replacement
--- | ---
gatttool | btgatt-client, D-Bus Gatt API[dead link 2023-10-29 ⓘ]
hciattach | btattach
hciconfig | btmgmt (and bluetoothctl?)
hcidump | btmon (and btsnoop)
hcitool | missing, D-Bus Device API[dead link 2023-10-29 ⓘ] available
rfcomm | missing, implement with D-Bus Profile1 API[dead link 2023-10-29 ⓘ]?
ciptool
sdptool | missing, functionality seems to be scattered over different D-Bus objects: Profile[dead link 2023-10-29 ⓘ], Advertising[dead link 2023-10-29 ⓘ], and the UUIDs arrays in device[dead link 2023-10-29 ⓘ] and adapter[dead link 2023-10-29 ⓘ].

### Service issues

#### systemd: Condition check resulted in Bluetooth service being skipped

`bluetooth.service` only requires the directory `/sys/class/bluetooth` to exist, which should be created by kernel module `bluetooth`, which is only autoloaded by `systemd-udev` if it actually finds a working Bluetooth hardware device.

If your `/sys/class/bluetooth` does not exist, check if your kernel Bluetooth module is loaded by `lsmod`. If not, and you believe you have a Bluetooth device, you can try manually starting them by loading the Bluetooth module and restarting `bluetooth.service`.

You should also load your corresponding kernel Bluetooth driver when loading the `bluetooth` module, most likely `btusb`, but can also be `btrtl,btintel,btbcm,bnep,btusb` etc.

Check `bluetooth.service`'s unit status to see whether it started.

See also Debian Bug report logs - #853207.

If `bluetooth.service` started successfully, there is a chance that you still cannot use Bluetooth normally (e.g. `bluetoothctl` says something like `org.Bluez.Error.NotReady` when you `scan on`). If this happens, try rebooting your computer, and double-check: whether directory `/sys/class/bluetooth` exists; whether `lsmod` includes correct Bluetooth modules; log messages in the journal; etc. `systemd-udev` should pickup your Bluetooth hardware automatically without manual changes again.

#### Bluetooth immediately waking up suspend-to-idle devices

On systems capable of suspend-to-idle/S2idle/S0ix/Modern Standby, Bluetooth controllers will stay enabled during sleep. This will usually cause the system to wake up immediately after going to sleep if any Bluetooth device is connected.

To prevent this, you can disable Bluetooth completely before going to sleep - install bluez-utils and create this file:

    /etc/systemd/system/bluetooth-disable-before-sleep.service

    [Unit]
    Description=Disable Bluetooth before going to sleep
    Before=sleep.target
    Before=suspend.target
    Before=hybrid-sleep.target
    Before=suspend-then-hibernate.target
    StopWhenUnneeded=yes

    [Service]
    Type=oneshot
    RemainAfterExit=yes

    ExecStart=/usr/bin/bluetoothctl power off
    ExecStop=/usr/bin/bluetoothctl power on

    [Install]
    WantedBy=sleep.target
    WantedBy=suspend.target
    WantedBy=hybrid-sleep.target
    WantedBy=suspend-then-hibernate.target

Enable this service and check if Bluetooth devices disconnect when going to sleep, and whenever Bluetooth goes back up after waking up the system.

If this workaround is in use, waking up the system with a Bluetooth mouse/keyboard will not work.

#### Bluetooth turns off after logout on a headless/server system

This can have various causes:

- Both PulseAudio and PipeWire run as user services by default, which are terminated once the last session ends. Enable lingering for the user to fix this.
- Additionally, when running WirePlumber with PipeWire (which is usually the case), WirePlumber runs a "logind-monitor" which enables Bluetooth on login and disables it on logout. See WirePlumber#Keep Bluetooth running after logout / Headless Bluetooth for a fix.

### Adapter issues

#### hcitool scan: Device not found

- On some laptops (e.g. Dell Studio 15, Lenovo Thinkpad X1) you have to switch the Bluetooth mode from HID to HCI. Install the bluez-hid2hci package, then udev should do this automatically. Alternatively, you can run this command to switch to HCI manually:

    # /usr/lib/udev/hid2hci

- If the device will not show up and you have a Windows operating system on your machine, try booting it and enable the Bluetooth adapter from windows.

- Sometimes also this simple command helps:

    # bluetoothctl power on

#### bluetoothctl: No default controller available

There is a bug with some motherboard bluetooth controllers. To see if this might be the issue, run `journalctl | grep hci`. If there are entries like "command tx timeout" or "Reading Intel version command failed", then power off your pc and physically unplug the power cable for a few seconds. This forces the controller to reload the firmware (while a standard reboot will not). See bug report here.

Make sure the device is not being blocked by rfkill.

If using USBGuard, make sure it does not block the device. See USBGuard#Allow Bluetooth controllers.

It might also happen with some intel cards (such as the 8260) to not be picked up correctly by the Bluetooth service. In some cases, using the deprecated bluez-deprecated-tools in lieu of bluez-utils have reportedly fixed the issue.

This might also be caused by power saving measures, in which case adding the kernel parameter `btusb.enable_autosuspend=n` is a potential solution. See also Red Hat Bugzilla – Bug 1573562.

Sometimes unloading and loading `btusb` without options helps to get the controller back:

    # modprobe -r btusb
    # modprobe btusb

It may also occur when the dongle is a CSR clone.

#### rfkill unblock: Do not unblock

If your device still soft blocked and you run ConnMan, try this:

    $ connmanctl enable bluetooth

#### Bluetooth USB dongle

If you are using a USB dongle, you should check that your Bluetooth dongle is recognized. You can do that by running `journalctl -f` as root when you have plugged in the USB dongle (or inspecting `/var/log/messages.log`). It should look something like the following (look out for hci):

    Feb 20 15:00:24 hostname kernel: [ 2661.349823] usb 4-1: new full-speed USB device number 3 using uhci_hcd
    Feb 20 15:00:24 hostname bluetoothd[4568]: HCI dev 0 registered
    Feb 20 15:00:24 hostname bluetoothd[4568]: Listening for HCI events on hci0
    Feb 20 15:00:25 hostname bluetoothd[4568]: HCI dev 0 up
    Feb 20 15:00:25 hostname bluetoothd[4568]: Adapter /org/bluez/4568/hci0 has been enabled

If you only get the first two lines, you may see that it found the device but you need to bring it up. Example:

    # btmgmt

    [mgmt]# info
    Index list with 1 item
    hci0:	Primary controller
    	addr 00:1A:7D:DA:71:10 version 6 manufacturer 10 class 0x000000
    	supported settings: powered connectable fast-connectable discoverable bondable link-security ssp br/edr hs le advertising secure-conn debug-keys privacy static-addr
    	current settings: connectable discoverable bondable ssp br/edr le secure-conn
    	name Mozart
    	short name

    [mgmt]# select hci0
    Selected index 0

    [hci0]# power up
    hci0 Set Powered complete, settings: powered connectable discoverable bondable ssp br/edr le secure-conn

    [hci0]# info
    hci0:	Primary controller
    	addr 00:1A:7D:DA:71:10 version 6 manufacturer 10 class 0x1c0104
    	supported settings: powered connectable fast-connectable discoverable bondable link-security ssp br/edr hs le advertising secure-conn debug-keys privacy static-addr
    	current settings: powered connectable discoverable bondable ssp br/edr le secure-conn

Or

    # bluetoothctl

    [bluetooth]# show
    Controller 00:1A:7D:DA:71:10 (public)
    	Name: Mozart
    	Alias: Mozart
    	Class: 0x0000095c
    	Powered: no
    	Discoverable: yes
    	Pairable: yes

    [bluetooth]# power on
    [CHG] Controller 00:1A:7D:DA:71:10 Class: 0x001c0104
    Changing power on succeeded
    [CHG] Controller 00:1A:7D:DA:71:10 Powered: yes

    [bluetooth]# show
    Controller 00:1A:7D:DA:71:10 (public)
    	Name: Mozart
    	Alias: Mozart
    	Class: 0x001c0104
    	Powered: yes
    	Discoverable: yes
    	Pairable: yes

To verify that the device was detected you can use `btmgmt` which is part of the `bluez-utils`. You can get a list of available devices and their identifiers and their MAC address by issuing:

    $ btmgmt info

    Index list with 1 item
    hci0:	Primary controller
    	addr 00:1A:7D:DA:71:10 version 6 manufacturer 10 class 0x1c0104
    	supported settings: powered connectable fast-connectable discoverable bondable link-security ssp br/edr hs le advertising secure-conn debug-keys privacy static-addr
    	current settings: powered connectable discoverable bondable ssp br/edr le secure-conn

It is possible to check the Bluetooth version as mapped to the HCI version according to the table in the official specification. For example, in the previous output, HCI version 6 is Bluetooth version 4.0.

More detailed information about the device can be retrieved by using the deprecated `hciconfig`. (bluez-deprecated-tools)

    $ hciconfig -a hci0

    hci0:   Type: USB
            BD Address: 00:1B:DC:0F:DB:40 ACL MTU: 310:10 SCO MTU: 64:8
            UP RUNNING PSCAN ISCAN
            RX bytes:1226 acl:0 sco:0 events:27 errors:0
            TX bytes:351 acl:0 sco:0 commands:26 errors:0
            Features: 0xff 0xff 0x8f 0xfe 0x9b 0xf9 0x00 0x80
            Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3
            Link policy: RSWITCH HOLD SNIFF PARK
            Link mode: SLAVE ACCEPT
            Name: 'BlueZ (0)'
            Class: 0x000100
            Service Classes: Unspecified
            Device Class: Computer, Uncategorized
            HCI Ver: 2.0 (0x3) HCI Rev: 0xc5c LMP Ver: 2.0 (0x3) LMP Subver: 0xc5c
            Manufacturer: Cambridge Silicon Radio (10)

##### Audio devices start to skip at short distance from dongle

If other devices share the same USB host, they can interrupt communication with audio devices. Make sure it is the only device attached to its bus. For example:

    $ lsusb

    Bus 002 Device 002: ID 0a12:0001 Cambridge Silicon Radio, Ltd Bluetooth Dongle (HCI mode)
    Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
    Bus 001 Device 004: ID 048d:1345 Integrated Technology Express, Inc. Multi Cardreader
    Bus 001 Device 003: ID 0424:a700 Standard Microsystems Corp. 2 Port Hub
    Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
    Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

##### CSR dongle 0a12:0001

The device `ID 0a12:0001 Cambridge Silicon Radio, Ltd Bluetooth Dongle (HCI mode)` has a regression bug, and currently only works in the kernel version 5.17 and < 6.0. For more information, see Kernel Bug 60824.

#### Logitech Bluetooth USB dongle

There are Logitech dongles (ex. Logitech MX5000) that can work in two modes: Embedded and HCI. In embedded mode dongle emulates a USB device so it seems to your PC that you are using a normal USB mouse/keyoard.

If you hold the little red Button on the USB BT mini-receiver it will enable the other mode. Hold the red button on the BT dongle and plug it into the computer, and after 3-5 seconds of holding the button, the Bluetooth icon will appear in the system tray. Discussion

Alternatively, you can install the bluez-hid2hci package. When you connect your Logitech dongle it will automatically switch.

#### Foxconn / Hon Hai / Lite-On Broadcom device

Some of these devices require the firmware to be flashed into the device at boot.

Some firmware is available when searching for broadcom on the AUR, a notable package being broadcom-bt-firmwareAUR, which provides the files for multiple cards.

Alternatively, the firmware can be converted from a Microsoft Windows .hex file into a .hcd using hex2hcd (which is installed with bluez-utils).

In order to get the right .hex file, try searching the device vendor:product code obtained with lsusb, for example:

    Bus 002 Device 004: ID 04ca:2006 Lite-On Technology Corp. Broadcom BCM43142A0 Bluetooth Device

or

    Bus 004 Device 004: Id 0489:e031 Foxconn / Hon Hai

Alternatively, boot into Windows (a virtual machine installation will suffice) and get the firmware name from the Device Manager utility. If you want to know the model of your device but cannot see it in lsusb, you might see it in lsusb -v as `iProduct`.

The .hex file can be extracted from the downloaded Windows driver without having to run Windows for it. Download the right driver, for example Bluetooth Widcomm[dead link 2023-09-16 ⓘ]. Depending on the format, extracting the files might need unrar or cabextract. To find out which of the many .hex files is the right one for you, look in the file `Win32/bcbtums-win7x86-brcm.inf` and search for `[RAMUSBE031.CopyList]`, where `E031` should be replaced with the product code (the second hex number in lsusb) of your device in upper-case. Underneath you should see the file name of the right .hex file.

Once you have the .hcd file, copy it into `/lib/firmware/brcm/BCM.hcd` - this filename is suggested by dmesg and it may change in your case so check your dmesg output in order to verify. Then reload the btusb module:

    # rmmod btusb
    # modprobe btusb

The device should now be available. See BBS#162688 for information on making these changes persistent.

#### Intel combined WiFi and Bluetooth cards

See Wireless network configuration#Bluetooth coexistence.

#### Mediatek MT7921 or MT7961 on dual boot with windows

On dual boot systems, if Bluetooth firmware versions are different for Windows and Linux, the Bluetooth adapter is not working after rebooting to Windows.

The best way to prevent this is updating the Bluetooth drivers (especially firmware) with latest version for each OS.

If you cannot find the latest version driver (or firmware) for Windows, you can copy the latest firmware file `/usr/lib/firmware/mediatek/BT_RAM_CODE_MT7961_1_2_hdr.bin.xz` from Arch Linux and extract to Windows (e.g. `C:\WINDOWS\system32\DRIVERS\`, you can find the firmware file path in the device manager on Windows).

#### Adapter disappears after suspend/resume

First, find vendor and product ID of the adapter. For example:

    $ lsusb -tv

    /:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/12p, 480M
        ID 1d6b:0002 Linux Foundation 2.0 root hub
        ...
        |__ Port 3: Dev 3, If 0, Class=Wireless, Driver=btusb, 12M
            ID 8087:0025 Intel Corp.
        |__ Port 3: Dev 3, If 1, Class=Wireless, Driver=btusb, 12M
            ID 8087:0025 Intel Corp.
        ...

In this case, the vendor ID is 8087 and the product ID is 0025.

Then, use usb_modeswitch to reset the adapter:

    # usb_modeswitch -R -v vendor_ID -p product_ID

### Pairing and connectivity issues

#### Computer is not visible

Enable discoverable mode if your computer cannot be discovered from your phone:

    # bluetoothctl discoverable on

Verify that discoverable mode is on:

    # bluetoothctl show

    	Powered: yes
    	Discoverable: yes
    	Pairable: yes

Note: Check `DiscoverableTimeout` and `PairableTimeout` in `/etc/bluetooth/main.conf`.

If the computer still does not show up, try changing the device class in `/etc/bluetooth/main.conf` as follows:

    # Default device class. Only the major and minor device class bits are
    # considered.
    #Class = 0x000100 # Computer Type (from default config)
    Class = 0x100100 # (Object-Transfer Service & Computer Type)

Note: In some cases, `Class` in `main.conf` gets overridden after device initialization, so set the class directly with `hciconfig hci0 class 100100`.

A user reported that this was the only solution to make their computer visible for their phone. LG TVs (and some others) are discoverable from their audio devices, so using `000414` (the soundbar class) will make such devices appear.

See https://bluetooth-pentest.narod.ru/software/bluetooth_class_of_device-service_generator.html to generate Bluetooth device/service classes.

#### Device connects, then disconnects after a few moments

If you see messages like the following in the journal, and your device fails to connect or disconnects shortly after connecting:

    bluetoothd: Unable to get connect data for Headset Voice gateway: getpeername: Transport endpoint is not connected (107)
    bluetoothd: connect error: Connection refused (111)

This may be because you have already paired the device with another operating system using the same Bluetooth adapter (e.g., dual-booting). Some devices cannot handle multiple pairings associated with the same MAC address (i.e., Bluetooth adapters). Follow instructions on #Dual boot pairing for solving this issue.

#### Device does not show up in scan

Some devices using Bluetooth low energy do not appear when scanning with bluetoothctl, for example the Logitech MX Master. You can use `transport le` to scan it.

    # bluetoothctl

    [bluetooth]# menu scan
    [bluetooth]# transport le
    [bluetooth]# back
    [bluetooth]# scan on
    [bluetooth]# devices
    ...
    Device XX:XX:XX:XX:XX:XX DA V2 X <---- low energy device here

Another way to connect them is by installing bluez-deprecated-tools, then start `bluetooth.service` and do:

    # bluetoothctl

    [NEW] Controller (MAC) myhostname [default]

    [bluetooth]# power on
    [CHG] Controller (MAC) Class: 0x0c010c
    Changing power on succeeded
    [CHG] Controller (MAC) Powered: yes

    [bluetooth]# scan on
    Discovery started
    [CHG] Controller (MAC) Discovering: yes

In another terminal:

    # hcitool lescan

Wait until your device shows up, then `Ctrl+c` hcitool. bluetoothctl should now see your device and pair normally.

#### No BLE device can be discovered with Intel Corp. AX200 Bluetooth

It seems that BLE passive scan is broken on this device. See upstream bug report for more details.

#### Cannot reconnect after sleep

You may notice that you cannot automatically reconnect to a device after it goes to sleep, or after the computer wakes from suspend.

You would for example notice the following errors in your logs:

    bluetoothd[487]: Authentication attempt without agent
    bluetoothd[487]: Access denied: org.bluez.Error.Rejected

This could be because the device is not marked as trusted. See #Pairing.

### Device-speific issues

#### Bluetooth mouse lags / disconnect / does not respond

See Bluetooth mouse#Troubleshooting.

#### Audio device fails to connect with br-connection-profile-unavailable

A bluetooth audio device will fail to connect if pipewire (rather than pulseaudio-bluetooth) is being used, but an instance of pipewire is not running. Start the `pipewire.service` user unit or play some audio to start the pipewire daemon, then try to connect the audio device again.

#### Interference between headphones and mouse

If you experience audio stuttering while using a Bluetooth mouse and keyboard simultaneously, you can try the following as referenced in #23 https://bugs.launchpad.net/ubuntu/+source/bluez/+bug/424215

    # hciconfig hci0 lm ACCEPT,MASTER
    # hciconfig hci0 lp HOLD,SNIFF,PARK

#### Continually connect/disconnect with TP-LINK UB400 and Xbox controller

Use the settings below:

    /etc/bluetooth/main.conf

    ...
    [General]
    JustWorksRepairing = always
    FastConnectable = true
    Class = 0x000100
    ...
    [GATT]
    ReconnectIntervals=1,1,2,3,5,8,13,21,34,55
    AutoEnable=true
    ...

Then restart the `bluetooth.service`.

You can see relevant discussion on xpadneo but the xpadneo driver is not needed.

### File transfer issues

#### gnome-bluetooth

If you see this when trying to enable receiving files in bluetooth-properties:

    Bluetooth OBEX start failed: Invalid path
    Bluetooth FTP start failed: Invalid path

Then make sure that the XDG user directories exist.

#### Cannot receive transferred files due to symlink

If incoming file transfers fail on an an otherwise functional Bluetooth connection, the problem may be due to symlinks in your file transfer path. Logs like this would appear in the journal:

    Jun 18 11:18:13 ember obexd[3338969]: open(/home/me/.cache/obexd/MOC740): Operation not permitted (1)

If the path shown in the error message contains a symlink, then obexd by default will not accept it. The behavior can be overridden on initialization using a drop-in file for the `obex.service` user service:

    ~/.config/systemd/user/obex.service.d/10-symlink.conf

    [Service]
    ExecStart=
    ExecStart=/usr/lib/bluetooth/obexd --symlinks

Then reload the systemd manager configuration of the calling user and restart the `obex.service` user unit.

## See also

- Keeping Bluetooth devices paired between Linux and Windows
- Bluetooth link keys on dual-boot systems

Category:

- Bluetooth

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