fence_ilo4: 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_ilo4 - from package: fence-agents

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

Error in other languages:
fence_ilo4: bevel nie gevind nie
fence_ilo4: comandă negăsită
fence_ilo4: comando não encontrado
fence_ilo4: commande introuvable
fence_ilo4: command not found
fence_ilo4: käsku ei ole
fence_ilo4: không tìm thấy lệnh
fence_ilo4: komanda nerasta
fence_ilo4: Kommando nicht gefunden.
fence_ilo4: kommandot finns inte
fence_ilo4: komut yok
fence_ilo4: nie znaleziono polecenia
fence_ilo4: níor aimsíodh an t-ordú
fence_ilo4: no se encontró la orden
fence_ilo4: no s'ha trobat l'ordre
fence_ilo4: opdracht niet gevonden
fence_ilo4: parancs nem található
fence_ilo4: perintah tidak ditemukan
fence_ilo4: príkaz nenájdený
fence_ilo4: příkaz nenalezen
fence_ilo4: команда не найдена
fence_ilo4: командата не е открита
fence_ilo4: 命令找不到
fence_ilo4: コマンドが見つかりません