frm_xfrd: 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/frm_xfrd - from package: xrootd-server

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

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