FreeFem++-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/FreeFem++-mpi - from package: freefem++

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

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