grubby: 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:

/sbin/grubby - from package: grubby

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

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