fence_sanlock: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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_sanlock - from package: fence-sanlock

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