zntune: 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/zntune - from package: atm-tools

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

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