srf_filter: 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/srf_filter - from package: staden-io-lib-utils

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

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