kwnnkill: 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/sbin/kwnnkill - from package: freewnn-kserver

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

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