Difference between revisions of "Music Player Daemon"

Revision as of 12:21, 4 December 2012

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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

Stable version

The latest stable version of mpd is available in the official repositories.

You may also want to install mpd-systemd.

Git version

Should users wish to run an experimental version, the AUR offers several from which to choose. For example, mpd-git^AUR.

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 intended 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, PulseAudio or OSS needs to be setup and working.

Global Configuration

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 is 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/lib/mpd 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 change permissions for mpd to write to /var/log/mpd/mpd.log, otherwise mpd will return an error when it is started. The best way is to make the /var/log/mpd/mpd.log belong to the mpd user.

  # chown -R mpd /var/log/mpd   

Run this to create the /run/mpd dir:

  # systemd-tmpfiles --create mpd.conf

To change the volume for mpd independent from other programs, uncomment or add this 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 software volume control in the 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
}

Changing the group that MPD runs as may result in 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, so add user mpd to group audio.

# gpasswd -a mpd audio

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
# systemctl restart mpd.service

Also see this forum thread.

An additional solution would be to just create a symbolic link into /var/lib/mpd/music.

# mkdir /var/lib/mpd/music
# ln -s MUSIC_FOLDER /var/lib/mpd/music/
# systemctl restart mpd.service

If the music collection is contained under multiple directories, create symbolic links under the main music directory in /var/lib/mpd. Remember to set permissions accordingly on the directories being linked.

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 daemon will use this directory to create mpd.pid in it. However, when running mpd as a different user, requires an update to the tmpfiles.d: copy /usr/lib/tmpfiles.d/mpd.conf to /etc/tmpfiles.d/mpd.conf: Change:

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. You'll need to install the mpc package for this. It is in the official repositories

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:

1. Since MPD is started as root by systemd, it first reads the /etc/mpd.conf file.
2. MPD reads the user variable in the /etc/mpd.conf file, and changes from root to this user.
3. 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.

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"

or you can use

sed "s/var\/lib\/mpd\/music/home\/$USER\/music/;
     s/var\/lib\/mpd/home\/$USER\/.mpd/;
     s/var\/run\/mpd/home\/$USER\/.mpd/;
     s/var\/log\/mpd/home\/$USER\/.mpd/" /etc/mpd.conf > ~/.mpd/mpd.conf

MPD can now be started by typing mpd on the command line.

To have MPD start with the X server add it to xprofile.

Start MPD per user with systemd

As recommanded above, it is best to use MPD as a service per user. In this case, we will use ~/.mpd/mpd.conf and not start mpd.service as a daemon for the whole system and all users. We will NOT use the /usr/lib/systemd/system/mpd.service which is intended to start the mpd.service as root and for all users. If you already enabled it, just disable it first:

 # systemctl disable mpd.service

If you used to start mpd inside your ~/.xinitrc, comment or delete the line

mpd ~/.mpdconf

Then, edit a new file /etc/systemd/user/mpd.service

/etc/systemd/user/mpd.service

[Unit]
Description = Music Player Daemon

[Service]
ExecStart = /usr/bin/mpd --no-daemon
Restart = always

[Install]
WantedBy = default.target

Then, add this line to .xinitrc

~/.xinitrc

#run systemd as user intsance
systemd --user &

Log out, log in your xsession. Let's first check mpd is not running. If yes, just kill it

$ ps -ef | grep mpd

Now, enable and start mpd.service as per user

$ systemctl --user enable mpd
$ systemctl --user start mpd

Check the mpd status and see if mpd.service is correctly enabled and started

$ systemctl --user status mpd

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).

Clients

A separate client is needed to control mpd. Popular options are:

Console

• mpc — Simple KISS client. All basic functionality available

http://mpd.wikia.com/wiki/Client:Mpc || mpc

• ncmpc — A NCurses client for mpd

http://mpd.wikia.com/wiki/Client:Ncmpc || ncmpc

• ncmpcpp — An almost exact clone of ncmpc with some new features written in C++ (tag editor, search engine)

http://unkart.ovh.org/ncmpcpp/ || ncmpcpp

• pms — Highly configurable and accessible ncurses client

http://pms.sourceforge.net/ || pmus^AUR

Graphical

• Ario — A very feature-rich GTK2 GUI client for mpd, inspired by Rhythmbox

http://ario-player.sourceforge.net/ || ario

• QmpdClient — A GUI client written with Qt 4.x

http://bitcheese.net/wiki/QMPDClient || qmpdclient

• Sonata — An elegant Python GTK+ client

http://sonata.berlios.de/ || sonata

• gmpc — GNOME Client

http://gmpc.wikia.com/wiki/Gnome_Music_Player_Client || gmpc

• Dmpc — Dmenu-based MPC client with a playlist manager and state-saving on playlist changes

http://wintervenom.mine.nu/ || dmpc^AUR

Web

• Patchfork — web client for MPD written in PHP and Ajax

http://mpd.wikia.com/wiki/Client:Pitchfork || patchfork-git^AUR.

See a long list of clients at the mpd wiki.

External links

• Sorted List of MPD Clients
• MPD forum