mbuild-hybrid: 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/mbuild-hybrid - from package: hybrid-dev

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

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