efibootmgr: 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/efibootmgr - from package: efibootmgr

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

On Debian possible default full paths are:

/bin/efibootmgr - from package: efibootmgr

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

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