xrd: 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/xrd - from package: xrootd-client

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

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