mbmon-rrd: 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/mbmon-rrd - from package: mbmon

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

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