interpfilter: 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/interpfilter - from package: ladr4-apps

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

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