qsfilter2: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/qsfilter2 - from package: libapache2-mod-qos

You may install the required package with command apt-get install {package}
Error in other languages:
qsfilter2: bevel nie gevind nie
qsfilter2: comandă negăsită
qsfilter2: comando não encontrado
qsfilter2: commande introuvable
qsfilter2: command not found
qsfilter2: käsku ei ole
qsfilter2: không tìm thấy lệnh
qsfilter2: komanda nerasta
qsfilter2: Kommando nicht gefunden.
qsfilter2: kommandot finns inte
qsfilter2: komut yok
qsfilter2: nie znaleziono polecenia
qsfilter2: níor aimsíodh an t-ordú
qsfilter2: no se encontró la orden
qsfilter2: no s'ha trobat l'ordre
qsfilter2: opdracht niet gevonden
qsfilter2: parancs nem található
qsfilter2: perintah tidak ditemukan
qsfilter2: príkaz nenájdený
qsfilter2: příkaz nenalezen
qsfilter2: команда не найдена
qsfilter2: командата не е открита
qsfilter2: 命令找不到
qsfilter2: コマンドが見つかりません