vmpk: 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/vmpk - from package: vmpk

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

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