dnping: 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/dnping - from package: dnet-progs

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

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