fence_emerson: 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_emerson - from package: fence-agents

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

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