DosMain_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 CentOS possible default full paths are:

/usr/lib64/openmpi/bin/DosMain_openmpi - from package: openmx-openmpi

You may install the required package with command yum install {package}

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