vdu: 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/sbin/vdu - from package: util-vserver

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

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