dhcpdump: 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/sbin/dhcpdump - from package: dhcpdump

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

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