nuauth: 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/nuauth - from package: nuauth

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

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