mpstore: 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 Debian possible default full paths are:

/usr/bin/mpstore - from package: mpdtoys

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

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