I have an Arch Linux install (running on a 3yo ASUS Zenbook UX31A) that works fine. But, when trying to fix some USB issues I started poking around and I don't seem to have a boot loader installed - or at least can figure out whatś the one I got.

Because of all the warnings and concern on the Installation Guide around UEFI, I tried to follow the instructions about booting, and partitions, as well as I could and, like I said, the system boots and work fine.

According to my pacman logs, efibootmgr was installed at the time, and I have it to this day, but it's not listed as a boot loader in the Arch Wiki (because it's not a boot loader, apparently)

I ran the bootinfoscript and it said:

=> No boot loader is installed in the MBR of /dev/sda.

I don't fully understand what boot loaders are and everything they do, so I might be missing something obvious, but shouldn't I have one? If not, how can my laptop boot without it?


Yes, it's possible to not have a boot loader in addition to the one in the computer's firmware (which is UEFI here). Well, that's not strictly true because in this case the Linux kernel functions as its own boot loader, if it is configured to include the EFI stub. This makes the kernel binary a valid EFI program which can be run directly from the UEFI firmware, thus closing the gap between the firmware present in the Flash ROM on the motherboard and the kernel image.

Usually a boot manager like systemd-boot is used together with an EFI stub kernel. A boot manager functions as a chooser program with which you can choose between several kernel versions or boot some other operating system (Windows, for example.) A boot loader like GRUB usually also includes a chooser, but it differs from a boot manager in that it includes functionality to actually load software from disk to memory. A boot loader must typically first load itself in several stages, then locate the kernel on the disk, load it into a predefined location in RAM, and finally start the kernel.

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