start-nas: 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/start-nas - from package: nas

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

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