vhd-update: 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/vhd-update - from package: blktap-utils

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

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