dndel: 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/dndel - from package: dnet-progs

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

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