Music Player Daemon

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MPD (music player daemon) is an audio player that has a server-client architecture. It plays audio files, organizes playlists and maintains a music database all while using very few resources. In order to interface with it, a separate client is needed.

Installation

Install mpd, available in the official repositories.

Setup

MPD is able to run globally (settings apply to all users), locally (per user settings), and in multiple instances. The way of setting up mpd depends on the way it is supposed to be used. A local configuration may prove more useful on a desktop system than on a system that is used by several people simultaneously.

For a comfortable use, it is sensible to provide MPD access to the following files and directories:

mpd.db    # The music database
mpd.pid   # The file where mpd stores its process ID
mpd.log   # mpd logs here
mpdstate  # mpd's current state is noted here
playlists # the folder where playlists are saved into

In order for MPD to be able to play back audio, ALSA or PulseAudio needs to be setup and working.

Global Configuration

Note: For a user-specific permissions, change the "user" line above to reflect one of the system users.

Warning: Users of PulseAudio with a local mpd have to implement a workaround in order to run mpd as its own user!

MPD comes with an example configuration file, available at /usr/share/doc/mpd/mpdconf.example. This file holds an abundance of information on MPD configuration, and holds default mixer values.

Normally,/etc/mpd.conf have been created when installing mpd. If not, copy the included example file to /etc/mpd.conf.

# cp /usr/share/doc/mpd/mpdconf.example /etc/mpd.conf

Editing mpd.conf

The default Arch install keeps the setup in /var and uses "mpd" as default user.

Edit /etc/mpd.conf to reflect as such:

/etc/mpd.conf

music_directory       "/home/user/music"
playlist_directory    "/var/lib/mpd/playlists"
db_file               "/var/lib/mpd/mpd.db"
log_file              "/var/log/mpd/mpd.log"
pid_file              "/run/mpd/mpd.pid"
state_file            "/var/lib/mpd/mpdstate"
user                  "mpd"
# bind_to_address       "127.0.0.1"
# port                  "6600"

Now you need to give permissions to mpd to write to /var/log/mpd/mpd.log, otherwise mpd will returns an error when started. Best is to make the /var/log/mpd/mpd.log belongs to mpd group

  # chown -R root:mpd /var/log/mpd

To change the volume of audio from mpd independent of other programs, uncomment or add the switch in mpd.conf:

/etc/mpd.conf

mixer_type			"software"

Users of PulseAudio will need to make the following modification:

/etc/mpd.conf

audio_output {
        type                    "pulse"
        name                    "pulse audio"
}

Users of ALSA will want to have the following device definition, which allows the software volume control in your MPD client to control the volume separately from other applications.

/etc/mpd.conf

audio_output {
        type            "alsa"
        name            "My Sound Card"
        mixer_type      "software"      # optional
}

Note that if you change the group that MPD runs as, you will get errors like "output: Failed to open "My ALSA Device"" "[alsa]: Failed to open ALSA device "default": No such file or directory" "player_thread: problems opening audio device while playing "Song Name.mp3""

This is because by default MPD runs as member of audio group and the sound devices under /dev/snd/ are owned by this group.

Music directory

MPD needs to have +x permissions on all parent directories to the music collection (ie. if it's located outside of "mpd" home directory /var/lib/mpd). By default useradd sets permissions on home directories to 1700 drwx------. Thus users will most likely need to remount the music directory under a directory that mpd has access to -- this only applies if running as the 'mpd' user.

# mkdir /var/lib/mpd/music
# echo "/home/$USER/music /var/lib/mpd/music none bind" >> /etc/fstab
# mount -a
# rc.d restart mpd

Creating the required files

Now, having finished configuring MPD, the files and directories for MPD to write in need to be created:

Create the directories and files specified in /etc/mpd.conf:

# mkdir -p /var/lib/mpd/playlists 
# touch /var/lib/mpd/{mpd.db,mpdstate}

Usually the init-script should properly create /run/mpd/ when starting. The deamon will use this directory to create mpd.pid in it. However: If you are running mpd as a different user, you will have to fix the tmpfiles.d: In /usr/lib/tmpfiles.d/mpd.conf change the line

d /run/mpd 0755 mpd mpd

to:

d /run/mpd 0755 username groupname

Change the file's permissions so that the daemon can modify them.

# chown -R mpd /var/lib/mpd

Create database

Creating the database is now accomplished via the update feature of the client, for example mpc update.

Note: Creating the MPD database as root using # mpd --create-db is deprecated.

Timeline of MPD startup

To depict when MPD drops its superuser privileges and assumes those of the user set in the configuration, the timeline of a normal MPD startup is listed here:

MPD is started on boot by /etc/rc.conf, by including it in the DAEMONS array. (Or, this can be done manually each session by running rc.d start mpd with root privileges).
Since MPD is now started as root, it first reads the /etc/mpd.conf file.
MPD reads the user variable in the /etc/mpd.conf file, and changes from root to this user.
MPD then reads the contents of the /etc/mpd.conf file and configures itself accordingly.

Notice that MPD changes the running user from root to the one named in the /etc/mpd.conf file. This way, uses of ~ in the configuration file point correctly to the home user's directory, and not root's directory. It may be worthwhile to change all uses of ~ to /home/username to avoid any confusion over this aspect of MPD's behavior.

Local Configuration (per user)

MPD does not need to be run globally as a daemon and can rather work per user. The usual method to configure MPD globally is because the listed files and folders in the default configuration file point to directories owned by root (the /var directory). A less used (but perhaps more sensible) method is to make MPD work with files and directories owned by a normal user. Running MPD as a normal user has the benefits of:

A single directory ~/.mpd (or any other directory under /home/username) that will contain all the MPD configuration files.
Easier to avoid unforeseen read/write permission errors.

Note: This approach will not work with multiple users to having access to MPD at the same time.

Begin the setup by creating a directory for the required files and the playlists:

mkdir -p ~/.mpd/playlists

Copy the contents of the default MPD configuration file in /usr/share/mpd/mpd.conf.example to the target user's home directory:

cp /usr/share/doc/mpd/mpdconf.example ~/.mpdconf

Create all of the requisite files:

touch ~/.mpd/{mpd.db,mpd.log,mpd.pid,mpdstate}

Edit ~/.mpdconf to specify these files:

~/.mpdconf

music_directory    "/home/USER/music"            # Keep commented if your XDG directory already points to it
playlist_directory "/home/USER/.mpd/playlists"
db_file            "/home/USER/.mpd/mpd.db"
log_file           "/home/USER/.mpd/mpd.log"
pid_file           "/home/USER/.mpd/mpd.pid"
state_file         "/home/USER/.mpd/mpdstate"

MPD can now be started by typing mpd on the command line. To have MPD start with the X server add it to ~/.xinitrc or create a .desktop if using a common desktop and save it to ~/.config/autostart/mpd.desktop:

mpd.desktop

[Desktop Entry]
Encoding=UTF-8
Version=0.9.4
Type=Application
Name=Music Player Daemon
Comment=
Exec=mpd
StartupNotify=false
Terminal=false
Hidden=false

Scripted Configuration

Rasi has written a script that will create the proper directory structure, configuration files and prompt for the location of the user's Music directory; it can be downloaded here.

Multi-mpd setup

Useful if running an icecast server.

For a second MPD (e.g., with icecast output to share music over the network) using the same music and playlist as the one above, simply copy the above configuration file and make a new file (e.g., /home/username/.mpd/config-icecast), and only change the log_file, error_file, pid_file, and state_file parameters (e.g., mpd-icecast.log, mpd-icecast.error, and so on); using the same directory paths for the music and playlist directories would ensure that this second mpd would use the same music collection as the first one e.g., creating and editing a playlist under the first daemon would affect the second daemon as well. Users do not have to create the same playlists all over again for the second daemon. Call this second daemon the same way from ~/.xinitrc above. (Just be sure to have a different port number, so as to not conflict with the first mpd daemon).