muffin: 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/muffin - from package: muffin

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

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