kernel_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/kernel_driver - from package: srtp-utils

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

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