dupload: 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/dupload - from package: dupload

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

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