xdelta3: 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/xdelta3 - from package: xdelta3

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

Error in other languages:
xdelta3: bevel nie gevind nie
xdelta3: comandă negăsită
xdelta3: comando não encontrado
xdelta3: commande introuvable
xdelta3: command not found
xdelta3: käsku ei ole
xdelta3: không tìm thấy lệnh
xdelta3: komanda nerasta
xdelta3: Kommando nicht gefunden.
xdelta3: kommandot finns inte
xdelta3: komut yok
xdelta3: nie znaleziono polecenia
xdelta3: níor aimsíodh an t-ordú
xdelta3: no se encontró la orden
xdelta3: no s'ha trobat l'ordre
xdelta3: opdracht niet gevonden
xdelta3: parancs nem található
xdelta3: perintah tidak ditemukan
xdelta3: príkaz nenájdený
xdelta3: příkaz nenalezen
xdelta3: команда не найдена
xdelta3: командата не е открита
xdelta3: 命令找不到
xdelta3: コマンドが見つかりません