ludevit_tk: 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/ludevit_tk - from package: ludevit

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

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