mpb-mpi: 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/mpb-mpi - from package: mpb-mpi

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

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