rdbx_driver: 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/lib/srtp/bin/rdbx_driver - from package: srtp-utils

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

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