upstart-monitor: 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/upstart-monitor - from package: upstart-monitor

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

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