fence_bullpap: 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
/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 Debian possible default full paths are:

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

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