systemd-boot

Assume you use Archlinux, and EFI system partition mount point is /boot.

Install:

bootctl --path=/boot install

Update:

bootctl update

Edit /boot/loader/loader.conf:

default         archlinux.conf
timeout         4
console-mode    max
editor          no

Edit /boot/loader/entries/archlinux.conf:

title       Arch Linux
linux       /vmlinuz-linux
initrd      /intel-ucode.img
initrd      /initramfs-linux.img
options     root="LABEL=ROOT" rw

Label root partition:

e2label /dev/XXX ROOT

View partitions:

blkid