mpd: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/mpd - from package: mpich2

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/mpd - from package: mpd

You may install the required package with command apt-get install {package}

Error in other languages:
mpd: bevel nie gevind nie
mpd: comandă negăsită
mpd: comando não encontrado
mpd: commande introuvable
mpd: command not found
mpd: käsku ei ole
mpd: không tìm thấy lệnh
mpd: komanda nerasta
mpd: Kommando nicht gefunden.
mpd: kommandot finns inte
mpd: komut yok
mpd: nie znaleziono polecenia
mpd: níor aimsíodh an t-ordú
mpd: no se encontró la orden
mpd: no s'ha trobat l'ordre
mpd: opdracht niet gevonden
mpd: parancs nem található
mpd: perintah tidak ditemukan
mpd: príkaz nenájdený
mpd: příkaz nenalezen
mpd: команда не найдена
mpd: командата не е открита
mpd: 命令找不到
mpd: コマンドが見つかりません