Arch Linux

Apoema

Member

Registered: 2020-10-26

Posts: 4

UEFI, GRUB and fast silent boot

Hi,

I am new to forum so I preemptily apologize for any mistake I shall make.

I am trying to the make my boot both faster and completely silent. I did read the Arch Linux Wiki page on Silent boot but no modification proposed altered my boot in any way and I am thinking it is mostly because I don't understand how the boot process work, I read some pages on the internet trying to understand it but while I learned a lot I still think that I am missing the big picture. Can anyone help me with that?

I am a old Linux user by now (12 years?) and I am using Arch since 2017 but I am entirely self taught so some technical process of Linux still evades me. I have a couple of questions:

- What does the GRUB actually does?

- Is Syslinux and systemd-boot alternatives to GRUB? Or they entirely different software?

- How does UEFI enters the equation here? My limited knowledge is that UEFI is a hardware dependent new implementation of the BIOS, am I correct? How are they different?

- By using UEFI can I ignore GRUB?

On a different but related note:

- Does Solid State Drives change the boot process in any way?

- Is there a hidden meaning between the /dev/sdaX and /dev/nvme0nXpX nomenclature?

- How does the windows option to fast startup work? I feel it is dependant of both the SSDs and the UEFI (but I don't understand) could I do something similar in Linux?

I will greatly appreciate any piece of knowledge that helps me understand these question. Thank you.

Scimmia

Fellow

Registered: 2012-09-01

Posts: 13,729

Re: UEFI, GRUB and fast silent boot

Start here, it will answer a number of your questions: https://www.happyassassin.net/posts/201 … work-then/

Apoema

Member

Registered: 2020-10-26

Posts: 4

Re: UEFI, GRUB and fast silent boot

Start here, it will answer a number of your questions: https://www.happyassassin.net/posts/201 … work-then/

This was a quite long and opinionated blog post but I learned a lot, thank you.

I notice that my hard drive is using a MBR partition table even though I am using UEFI (or so I think, `efibootmgr -v` does work as expected), which might be the source of my boot *problems*.

But, before that, I still have questions if anyone is willing to help.

I am very curious about how the old BIOS worked. The article says that the BIOS way to boot is to read a *magical* part of the disk that will have instructions about what to do next. But the BIOS is motherboard dependent right? And the HD/SSD I provide is empty (or am I wrong?), how does the very first boot work? Is there a tiny disk inside the motherboard with BIOS instructions to search for a input (HD/CD/USB) and run a specific file in that disk?

Now about the UEFI, I got that UEFI is so much more than BIOS, but what can we do if that? Aside from Secure Booting. Should I understand that the GRUB is a consequence of the BIOS limitation and is outdated now that we have UEFI?

Finally Secure Boot, should I care about it? I don't use any exotic kernel nor a NVIDIA driver, should I try to implement it?

Last edited by Apoema (2020-10-26 05:07:32)

GaKu999

Member

From: US/Eastern

Registered: 2020-06-21

Posts: 696

Re: UEFI, GRUB and fast silent boot

AFAIK...

I notice that my hard drive is using a MBR partition table even though I am using UEFI (or so I think, `efibootmgr -v` does work as expected), which might be the source of my boot *problems*.

You are the one that defines the {HD,SS}D partition table, it's common to see GPT with a protective MBR to avoid...derps from derpy implementations and etc...
There's also a hybrid GPT for when the one want's to be able to boot the medium in both BIOS&UEFI.
And plain o'l MBR for when the firmware or BIOS just doesn't do GPT at all and hybrid causes problems.
You can also use GPT without the protective MBR...

There's also the possibility of having the storage as only a filesystem, like a full btrfs, but since the ESP must be loaded from somewhere, that's hardly bootable...

But the BIOS is motherboard dependent right?
And the HD/SSD I provide is empty (or am I wrong?), how does the very first boot work?
Is there a tiny disk inside the motherboard with BIOS instructions to search for a input (HD/CD/USB) and run a specific file in that disk?

1- The old BIOS was sort-of "standard", but of course, as with UEFI, most vendors had their own quirks and breakage...
2- If the {HD,SS}D is blank, the very first boot is...POST and complain about missing bootable medium.
3- Usually a ROM with the entire BIOS/UEFI, usually the MB specs show where it is. IIRC it's something tiny, close to 2MiBs in most cases, looks like a "chip" soldered to the MB.

Finally Secure Boot, should I care about it? I don't use any exotic kernel nor a NVIDIA driver, should I try to implement it?

That's up to you, there's a lot of different opinions on Secure Boot, how effective it really is, and if it can actually protect you.
Anyone with physical access can just bypass anything...

If you don't have a reason for the trouble I'd suggest to ignore it, and disregard it as something the vendors (mainly M$) want to push as...whatever.
But that's up to you, since ^ is just my POV about it.

In the case one needs boot security there are better means to provide it, instead of depending of the MB quirks.
Not every vendor gives a flexible access to Secure Boot, with certain broken implementations...

---

My repos • Some snippets

Heisenberg might have been here.

Apoema

Member

Registered: 2020-10-26

Posts: 4

Re: UEFI, GRUB and fast silent boot

Thank you Gaku about the information, about this:

AFAIK...

I notice that my hard drive is using a MBR partition table even though I am using UEFI (or so I think, `efibootmgr -v` does work as expected), which might be the source of my boot *problems*.

You are the one that defines the {HD,SS}D partition table, it's common to see GPT with a protective MBR to avoid...derps from derpy implementations and etc...
There's also a hybrid GPT for when the one want's to be able to boot the medium in both BIOS&UEFI.
And plain o'l MBR for when the firmware or BIOS just doesn't do GPT at all and hybrid causes problems.
You can also use GPT without the protective MBR...

There's also the possibility of having the storage as only a filesystem, like a full btrfs, but since the ESP must be loaded from somewhere, that's hardly bootable...

I am the derp derping the implementation. I just learned about the importance of GPT to UEFI so I probably just went with the familiar when I installed arch in my machine.

I have a new question about that, if I were to decide to fix it I would have to format the whole disk. Is there a way for me to create a back up of my system so I can reinstall arch as I have it now? That is keep, my packages and configuration intact?

I still in doubt about the relevance of GRUB after UEFI though...

Scimmia

Fellow

Registered: 2012-09-01

Posts: 13,729

Re: UEFI, GRUB and fast silent boot

Grub is a bootloader. The bootloader's job is loading the kernel and initramfs into memory and turning control over o the kernel. The kernel also has a small bootloader built into it, so that one can be used directly from the firmware's boot manager, or via a 3rd party boot manager (systemd-boot, refind, etc).

How those relate to UEFI is that they're UEFI executables that the firmware runs.

Apoema

Member

Registered: 2020-10-26

Posts: 4

Re: UEFI, GRUB and fast silent boot

Grub is a bootloader. The bootloader's job is loading the kernel and initramfs into memory and turning control over o the kernel. The kernel also has a small bootloader built into it, so that one can be used directly from the firmware's boot manager, or via a 3rd party boot manager (systemd-boot, refind, etc).

How those relate to UEFI is that they're UEFI executables that the firmware runs.

Which one is UEFI executable? The GRUB, the Kernel boot manager or both?

This is the picture I have so far of the boot process:

UEFI or BIOS > GRUB > Kernel/initramfs > Boot manager (> System Services > Display manager)

Is that fairly accurate?

Scimmia

Fellow

Registered: 2012-09-01

Posts: 13,729

Re: UEFI, GRUB and fast silent boot

https://wiki.archlinux.org/index.php/Arch_boot_process