xrdcp-old: 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/xrdcp-old - from package: xrootd-client

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

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