pkndvi: 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/pkndvi - from package: pktools

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

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