xdelta-config: 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 CentOS possible default full paths are:

/usr/bin/xdelta-config - from package: xdelta-devel

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/xdelta-config - from package: xdelta

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

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