VolumeControl: 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/VolumeControl - from package: volumecontrol.app

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

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