key-mon: 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/key-mon - from package: key-mon

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

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