fence_xvm: 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/sbin/fence_xvm - from package: fence-virt

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

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