nns: 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 CentOS possible default full paths are:

/usr/bin/nns - from package: tcllib

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/nns - from package: tcllib

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

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