mudlogd: command not found

Have You tried accessing the binary with the full path?

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/mudlogd - from package: muddleftpd

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