rtpw: 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/rtpw - from package: srtp-utils

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

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