medusa: 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/medusa - from package: medusa

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

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