nnusage: 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/nnusage - from package: nn

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

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