fence_sanbox2: 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_sanbox2 - from package: fence-agents

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

On Debian possible default full paths are:

/usr/sbin/fence_sanbox2 - from package: fence-agents

You may install the required package with command apt-get install {package}

Error in other languages:
fence_sanbox2: bevel nie gevind nie
fence_sanbox2: comandă negăsită
fence_sanbox2: comando não encontrado
fence_sanbox2: commande introuvable
fence_sanbox2: command not found
fence_sanbox2: käsku ei ole
fence_sanbox2: không tìm thấy lệnh
fence_sanbox2: komanda nerasta
fence_sanbox2: Kommando nicht gefunden.
fence_sanbox2: kommandot finns inte
fence_sanbox2: komut yok
fence_sanbox2: nie znaleziono polecenia
fence_sanbox2: níor aimsíodh an t-ordú
fence_sanbox2: no se encontró la orden
fence_sanbox2: no s'ha trobat l'ordre
fence_sanbox2: opdracht niet gevonden
fence_sanbox2: parancs nem található
fence_sanbox2: perintah tidak ditemukan
fence_sanbox2: príkaz nenájdený
fence_sanbox2: příkaz nenalezen
fence_sanbox2: команда не найдена
fence_sanbox2: командата не е открита
fence_sanbox2: 命令找不到
fence_sanbox2: コマンドが見つかりません