tucnak: 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
/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/tucnak - from package: tucnak2

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