NPopenmpi: 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/NPopenmpi - from package: netpipe-openmpi

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

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