grub-ntldr-img: 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/bin/grub-ntldr-img - from package: grub-pc

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

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