filterdup: 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/filterdup - from package: macs

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

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