xmms2-mlib-updater: 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/xmms2-mlib-updater - from package: xmms2-client-medialib-updater

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

Error in other languages:
xmms2-mlib-updater: bevel nie gevind nie
xmms2-mlib-updater: comandă negăsită
xmms2-mlib-updater: comando não encontrado
xmms2-mlib-updater: commande introuvable
xmms2-mlib-updater: command not found
xmms2-mlib-updater: käsku ei ole
xmms2-mlib-updater: không tìm thấy lệnh
xmms2-mlib-updater: komanda nerasta
xmms2-mlib-updater: Kommando nicht gefunden.
xmms2-mlib-updater: kommandot finns inte
xmms2-mlib-updater: komut yok
xmms2-mlib-updater: nie znaleziono polecenia
xmms2-mlib-updater: níor aimsíodh an t-ordú
xmms2-mlib-updater: no se encontró la orden
xmms2-mlib-updater: no s'ha trobat l'ordre
xmms2-mlib-updater: opdracht niet gevonden
xmms2-mlib-updater: parancs nem található
xmms2-mlib-updater: perintah tidak ditemukan
xmms2-mlib-updater: príkaz nenájdený
xmms2-mlib-updater: příkaz nenalezen
xmms2-mlib-updater: команда не найдена
xmms2-mlib-updater: командата не е открита
xmms2-mlib-updater: 命令找不到
xmms2-mlib-updater: コマンドが見つかりません