mpy.openmpi: 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/lib/debug/usr/lib/yorick/bin/mpy.openmpi - from package: yorick-dbg
/usr/bin/mpy.openmpi - from package: yorick-mpy-openmpi
/usr/lib/yorick/bin/mpy.openmpi - from package: yorick-mpy-openmpi

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

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