xdu: 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/xdu - from package: xdu

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

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