mgm: 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/mgm - from package: mgm

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

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