dhcp_probe: 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/dhcp_probe - from package: dhcp-probe

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

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