xmlwf21: 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/xmlwf21 - from package: expat21

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

Error in other languages:
xmlwf21: bevel nie gevind nie
xmlwf21: comandă negăsită
xmlwf21: comando não encontrado
xmlwf21: commande introuvable
xmlwf21: command not found
xmlwf21: käsku ei ole
xmlwf21: không tìm thấy lệnh
xmlwf21: komanda nerasta
xmlwf21: Kommando nicht gefunden.
xmlwf21: kommandot finns inte
xmlwf21: komut yok
xmlwf21: nie znaleziono polecenia
xmlwf21: níor aimsíodh an t-ordú
xmlwf21: no se encontró la orden
xmlwf21: no s'ha trobat l'ordre
xmlwf21: opdracht niet gevonden
xmlwf21: parancs nem található
xmlwf21: perintah tidak ditemukan
xmlwf21: príkaz nenájdený
xmlwf21: příkaz nenalezen
xmlwf21: команда не найдена
xmlwf21: командата не е открита
xmlwf21: 命令找不到
xmlwf21: コマンドが見つかりません