ns820-diag: 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/ns820-diag - from package: nictools-pci

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

Error in other languages:
ns820-diag: bevel nie gevind nie
ns820-diag: comandă negăsită
ns820-diag: comando não encontrado
ns820-diag: commande introuvable
ns820-diag: command not found
ns820-diag: käsku ei ole
ns820-diag: không tìm thấy lệnh
ns820-diag: komanda nerasta
ns820-diag: Kommando nicht gefunden.
ns820-diag: kommandot finns inte
ns820-diag: komut yok
ns820-diag: nie znaleziono polecenia
ns820-diag: níor aimsíodh an t-ordú
ns820-diag: no se encontró la orden
ns820-diag: no s'ha trobat l'ordre
ns820-diag: opdracht niet gevonden
ns820-diag: parancs nem található
ns820-diag: perintah tidak ditemukan
ns820-diag: príkaz nenájdený
ns820-diag: příkaz nenalezen
ns820-diag: команда не найдена
ns820-diag: командата не е открита
ns820-diag: 命令找不到
ns820-diag: コマンドが見つかりません