fence_nss_wrapper: 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 Debian possible default full paths are:

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

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

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