Bluetooth

Enabling Bluetooth support

To enable support for Bluetooth devices, add hardware.bluetooth.enable to /etc/nixos/configuration.nix:

{
  ...
  hardware.bluetooth.enable = true;
  ...
}

Tip

In order to affect your NixOS system by your nix-language-specific changes you must first evaluate it:

$ nixos-rebuild switch --use-remote-sudo

Pairing Bluetooth devices

In order to use Bluetooth devices, they must be paired with your NixOS machine. Heavier desktop environments will usually provide a Bluetooth management GUI which you can use to pair devices.

If your desktop environment does not provide such a GUI, you can additionally enable the blueman service, which provides blueman-applet and blueman-manager with the snippet below.

services.blueman.enable = true;

Pairing devices from the command line

Alternatively, Bluetooth devices can be paired from the command line using bluetoothctl.

$ bluetoothctl
[bluetooth] # power on
[bluetooth] # agent on
[bluetooth] # default-agent
[bluetooth] # scan on
...put device in pairing mode and wait [hex-address] to appear here...
[bluetooth] # pair [hex-address]
[bluetooth] # connect [hex-address]

Bluetooth devices automatically connect with bluetoothctl as well:

$ bluetoothctl
[bluetooth] # trust [hex-address]

Using Bluetooth headsets with PulseAudio

To allow Bluetooth audio devices to be used with PulseAudio, amend /etc/nixos/configuration.nix as follows:

{
  ...
  hardware.pulseaudio = {
    enable = true;

    # NixOS allows either a lightweight build (default) or full build of PulseAudio to be installed.
    # Only the full build has Bluetooth support, so it must be selected here.
    package = pkgs.pulseaudioFull;
  };

  hardware.bluetooth.enable = true;
  ...
}

Tip

In order to affect your NixOS system by your nix-language-specific changes you must first evaluate it:

$ nixos-rebuild switch --use-remote-sudo

You will need to restart PulseAudio; try systemctl --user daemon-reload; systemctl --user restart pulseaudio.

You can verify that PulseAudio has loaded the Bluetooth module by running pactl list | grep -i 'Name.*module.*blue'; Bluetooth modules should be present in the list.

Using Bluetooth headset buttons to control media player

Some bluetooth headset have buttons for pause/play or to skip to the next track. To make these buttons usable with media players supporting the dbus-based MPRIS standard, one can use mpris-proxy that is part of bluez package. The following snippet can be used in Home Manager to start this program as a daemon:

systemd.user.services.mpris-proxy = {
  Unit.Description = "Mpris proxy";
  Unit.After = [ "network.target" "sound.target" ];
  Service.ExecStart = "${pkgs.bluez}/bin/mpris-proxy";
  Install.WantedBy = [ "default.target" ];
};

System-Wide PulseAudio

This article or section needs expansion.

Reason: When setting up pulseaudio systemWide extra policies needs to be deployed for pulse to be able to connect to the bluetooth stack. The Info below is not enough. (Discuss in Talk:Bluetooth#)
Please consult the pedia article metapage for guidelines on contributing.

When you are running PulseAudio system-wide then you will need to add the following modules to your default.pa configuration:

hardware.pulseaudio.configFile = pkgs.writeText "default.pa" ''
  load-module module-bluetooth-policy
  load-module module-bluetooth-discover
  ## module fails to load with 
  ##   module-bluez5-device.c: Failed to get device path from module arguments
  ##   module.c: Failed to load module "module-bluez5-device" (argument: ""): initialization failed.
  # load-module module-bluez5-device
  # load-module module-bluez5-discover
'';

Enabling extra codecs

WARNING: The hardware.pulseaudio.extraModules option is only available in the 19.03 release or later.

While pulseaudio itself only has support for the SBC bluetooth codec there is out-of-tree support for AAC, APTX, APTX-HD and LDAC.

To enable extra codecs add the following to /etc/nixos/configuration.nix:

{
...
  hardware.pulseaudio = {
    enable = true;
    extraModules = [ pkgs.pulseaudio-modules-bt ];
    package = pkgs.pulseaudioFull;
  };
...
}

Enabling A2DP Sink

Modern headsets will generally try to connect using the A2DP profile. To enable this for your bluetooth connection, add the following to /etc/nixos/configuration.nix

{
...
hardware.bluetooth.extraConfig = "
  [General]
  Enable=Source,Sink,Media,Socket
";
...
}

This configuration may be unnecessary and does not work with bluez5 (Unknown key Enable for group General ).

Managing audio devices

pavucontrol can be used to reconfigure the device:

To enable A2DP, change the profile to “High Fidelity Playback (A2DP Sink)” on the “Configuration” tab.
To set the device as the default audio output, select “set as fallback” on the “Output Devices” tab.

Alternatively, the device can be configured via the command line:

To enable A2DP, run:

$ pacmd set-card-profile "$(pactl list cards short | egrep -o bluez_card[[:alnum:]._]+)" a2dp_sink

To set the device as the default audio output, run:

$ pacmd set-default-sink "$(pactl list sinks short | egrep -o bluez_sink[[:alnum:]._]+)"

Troubleshooting

USB device needs to be unplugged/re-plugged after suspend

Some USB device/host combinations don't play well with the suspend/resume cycle, and need to be unplugged and then re-plugged to work again.

It is possible to simulate a unplug/re-plug cycle using the /sys filesystem.

This gist provides a script and instructions to set-up a workaround for these devices.

When connecting to an audio device: Failed to connect: org.bluez.Error.Failed

You need to use pulseaudioFull, see #Using Bluetooth headsets with PulseAudio.

Bluetooth fails to power on with Failed to set power on: org.bluez.Error.Blocked

If journalctl -eu bluetooth shows Failed to set mode: Blocked through rfkill (0x12), rfkill might be blocking it:

$ rfkill
ID TYPE      DEVICE      SOFT      HARD
 1 wlan      phy0   unblocked unblocked
37 bluetooth hci0   blocked unblocked

Unblock it first:

$ sudo rfkill unblock bluetooth

Cannot use bluetooth while it previously worked

Symptoms:

When using bluetoothctl, getting "No agent is registered".
When using blueman or anything using dbus to talk to bluez, getting dbus.exceptions.DBusException: org.freedesktop.DBus.Error.AccessDenied: Rejected send message"

This possibly can be fixed by restarting the display-manager session. The session management may have had an issue with registering your current session and doesn't allow you to control bluetooth.

sudo systemctl restart display-manager.service