fence_rsa: 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_rsa - 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_rsa - from package: fence-agents

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

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