No more boot loader: Please use the kernel instead

https://pretalx.com/devconf-cz-2024/talk/W3AVCT/

by zdw • 2 years ago

794 445 2 years ago

drewg1232• 2 years ago

I personally think they're moving in the wrong direction. I'd rather have "NMIRFS" (no more initramfs). Eg, a smarter bootloader that understands all bootable filesystems and cooperates with the kernel to pre-load modules needed for boot and obviates the need for initramfs.

FreeBSD's loader does this, and its so much easier to deal with. Eg, it understands ZFS, and can pre-load storage driver modules and zfs.ko for the kernel, so that the kernel has everything it needs to boot up. It also understands module dependencies, and will preload all modules that are needed for a module you specify (similar to modprobe).

ta86452• 2 years ago

The Linux kernel does not require an initramfs. You can build a kernel with everything compiled in; with no modules needed at all. Initramfs is used for generic kernels where you don't know beforehand which features will be required. This allows you to avoid wasting RAM on features you don't use. But it is optional.

Muromec2• 2 years ago

I think the idea is, since modules map to device ids statically, bootloader could have enough information to read them from the filestem one by one.

I don’t see the point of doing so however.

jolmg• 2 years ago

Initramfs is used for generic kernels where you don't know beforehand which features will be required.

And also for e.g. cases where you've got some custom stack of block devices that you need to set up before the root FS and other devices can be mounted. It's not just about loading kernel modules.

drewg1232• 2 years ago

I realize that. But every distro I've used uses an initramfs, so unless you want to build your own kernels, you're stuck with it, and the painfully slow initramfs updates when you update packages, and dkms (or similar) updates the initramfs with the newer version of your out-of-tree modules.

linsomniac• 2 years ago

Is anyone really wanting to get back into the business of building their own kernels? I started using Linux heavily in '92, and I've built a lot of kernels, and am quite happy to not be building them anymore.

arp242• 2 years ago

What's the reason it doesn't load those modules from the regular filesystem? That's what FreeBSD does, and seems to work well enough?

Aurornis• 2 years ago

I'd rather have "NMIRFS" (no more initramfs).

In many cases, you don't need initramfs. I rarely use one in embedded systems.

fullstop2• 2 years ago

I use them in embedded systems because they allow me to mount encrypted volumes without exposing the keys.

Arnavion7• 2 years ago

Linux has multiple choices for filesystems for root, even if you only count the most popular ones. And on top of that they could be encrypted by LUKS. Duplicating all that into the bootloader is what GRUB does, and poorly. Putting the kernel into the ESP is much better in that regard.

m4632• 2 years ago

I personally think they're moving in the wrong direction

the other direction is to put everything in systemd. :)

markhahn2• 2 years ago

bad thing to joke about.

aaronmdjones4• 2 years ago

As other sibling comments have explained, an initramfs is usually optional for booting Linux.

If you build the drivers for your storage media and filesystem into the kernel (not as a module), and the filesystem is visible to the kernel without any userland setup required beforehand (e.g. the filesystem is not in an LVM volume, not on an MD-RAID array, not encrypted), it is fully capable of mounting the real root filesystem and booting init directly from it.

The only point of consideration is that it doesn't understand filesystem UUIDs or labels (this is part of libuuid which is used by userland tools like mount and blkid), so you have to specify partition UUIDs or labels instead (if you want to use UUIDs or labels). For GPT disks, this is natively available (e.g. root=PARTUUID=4F68BCE3-E8CD-4DB1-96E7-FBCAF984B709 or root=PARTLABEL=Root). For MS-DOS disks, this is emulated for UUIDs only by using the disk ID and partition number (e.g. root=PARTUUID=11223344-02).

You can also specify the device name directly (e.g. root=/dev/sda2) or the major:minor directly (e.g. root=08:02), but this is prone to enumeration order upset. If you can guarantee that this is the only disk it will ever see, or that it will always see that disk first, this is often the most simple approach, but these days I use GPT partition UUIDs.

mlyle• 2 years ago

Yes, I think he realizes it's optional for booting Linux.

In practice, we have generic kernels which require a lot of stuff in modules for real user systems running on distributions. Instead, though, we could have a loader which doesn't require this big relatively-opaque blob and instead loads the modules necessary at boot time (and does any necessary selection of critical boot devices). i.e. like FreeBSD does.

There's advantages each way. You can do fancier things with an initramfs than you ever could do in the loader. On the other hand, you can change what's happening during boot (e.g. loading different drivers) without a lot of ancillary tooling to recover a system.

the_duke• 2 years ago

I think you just reinforced the parents point.

StillBored2• 2 years ago

Not entirely, it is possible for simple boot solutions, but to enable LUKS and various other rootfs, it usually requires some userspace probing, authentication, etc. I'm not so sure it would be easy to convince the kernel maintainers to add a user prompt for pin code to the kernel just to avoid having an initrd.

zdw• 2 years ago

FWIW, Grub has a read-only ZFS implementation to allow booting: https://git.savannah.gnu.org/cgit/grub.git/tree/include/grub...

nubinetwork3• 2 years ago

Grub uses an ancient version of zfs code, it's tied to Oracle's zfs and they refuse to update it to current openzfs.

E39M5S624• 2 years ago

Ditch grub and use Linux to boot Linux on ZFS - https://docs.zfsbootmenu.org/en/v2.3.x/ .

mjg5918• 2 years ago

This requires a bunch of additional logic in the bootloader (eg, providing disk encryption keys), and since you're not doing this in a fully-featured OS environment (as you are in the initramfs case) it's going to be hard providing a consistent experience through the entire boot process. Having the pre-boot environment be a (slightly) cut-down version of the actual OS means all your tooling can be shared between the two environments.

sim7c00• 2 years ago

this exactly. freebsd's loader is one of the only sane ones ive seen. grub is an amazing piece of software but its really a mess to work with.

zauguin• 2 years ago

This is a step in that direction. What they are proposing is not so much "no bootloader" but using a small Linux as bootloader. I'm using a similar setup for some time and it gives some of these advantages. Especially you get support for all relevant filesystems (you can support everything Linux supports because it is Linux), it can dynamically build a minimal initramfs with only the needed drivers if you want to and understands module dependencies (e.g. it can just dump the list of modules it uses itself) and is generally much more flexible.

rcxdude10• 2 years ago

Does FreeBSD's loader share code with the kernel? It does seem like a lot of duplication of systems to make it work in comparison to just using the same code.

fooker• 2 years ago

The more smartness you put here, the more it makes life difficult for non-standard operating systems.

And if this bit is closed source, and something doesn't work, you don't have a recourse.

dexen• 2 years ago

Seconding this.

Having lucked into using Lilo and no initramfs for several years now, I'm very happy with robustness and straightforwardness of the solution.

In contrast, on the rare occasion I've dealt with somebody elses' GRUB and initramfs setups, they turn out brittle and complex.

the_panopticon• 2 years ago

Seems to be a trend including work like https://www.linuxboot.org/.

theteapot• 2 years ago

Isn't one of the use cases in GRUB choosing which kernel you want to load?

SahAssar• 2 years ago

Via EFI probably.

m4632• 2 years ago

Does that mean the UI you will use to choose the kernel will probably be the bios?

gjsman-1000• 2 years ago

That’s the neat part - you install GRUB if that’s something you care about. For the 98+% who will always use the newest kernel, and can tell the system to (hypothetically) use a different kernel on future reboots after the system has loaded, it won’t be an issue.

Shorel2• 2 years ago

They address this use case in the video. Their loader can show a menu.

devit• 2 years ago

You can use kexec to load a different Linux kernel from a Linux kernel.

Probably slower and perhaps less compatible than using GRUB though.

Arnavion7• 2 years ago

I can't open the .odp file right now, but:

We (Red Hat boot loader engineering) will present our solution to this problem, which is to use the Linux kernel as its own bootloader. Loaded by the EFI stub on UEFI, and packed into a unified kernel image (UKI), the kernel, initramfs, and kernel command line, contain everything they need to reach the final boot target. All necessary drivers, filesystem support, and networking are already built in and code duplication is avoided.

That has been doable for a few years already. What's the new part?

alright2565• 2 years ago

Maybe it's just a convenient script to put this stuff together? Looks like they have a website for this too: https://fizuxchyk.wordpress.com/2024/06/13/nmbl-we-dont-need...

I'm not really sure I understand either, I've had this bootloader-free setup working great for quite a few years on my machines too.

Arnavion7• 2 years ago

Ah, so another Stratis then.

saghm2• 2 years ago

Right before that paragraph, they cite issues with GRUB as a motivation for this work. What confuses me is that Redhat already has a GRUB replacement in systemd-boot. Is this work intended to obviate that as well, or is it going to relate to it somehow? I imagine doing all this and tying it to systemd would generate some backlash like usual (although at this point, it seems unlikely that this would affect the plans given how few distros don't use systemd).

Arnavion7• 2 years ago

I imagine doing all this and tying it to systemd would generate some backlash like usual (although at this point, it seems unlikely that this would affect the plans given how few distros don't use systemd).

systemd-boot is independent of systemd. It's called "systemd-" because it's under the same "group of core OS software" umbrella named "systemd", but otherwise it can be compiled independently, does not require the OS to be using systemd, etc.

Edit: I also wrote originally that switching to systemd-boot would also require switching the kernel from vmlinuz+initramfs to a UKI, but I forgot systemd-boot does support vmlinuz+initramfs through explicit loader entries config.

oneplane• 2 years ago

I agree, I don't think this is actually 'new' at all. We have had EFI Stubs, KExec/KSplice (Heads as a loader distro for example) and non-GRUB options for a while.

At best, this approach doesn't make the boot loader 'go away', it just moves that task to EFI. Which means you depend on EFI instead of GRUB. This isn't really different from say, U-Boot, where you have a bootrom (usually in the SoC or ROM) that does bringup, then U-boot as an intermediary, and then the Linux Kernel. Same deal with BSP and Coreboot, or Bochs or any of the other boot protocol launchers.

Maybe if their scope is the narrowest of all the scopes (only x86 and only UEFI 2.0 and higher and only specific distros) it might make sense, just to have it be invented in-house as a fake moat. But the end-user doesn't really benefit (as there is no change), and other distros are unlikely to care. You do get a dependency on IBVs and OEMs to implement their UEFI correctly, which most have a hard time doing as it is. And you can't re-use it anywhere else, except maybe SystemReady ARM servers.

andrewstuart• 2 years ago

I’m fairly technical but I have to say grasping the field of partitions , booting, boot loaders grub uefi its alternatives and the various combinations thereof in Linux defeated me.

When learning something I try to find the simple path, a reliable minimum that gets to the goal. I never found it.

Complexity is the word that comes to mind.

Muromec2• 2 years ago

Thankfully we have none of that on embedded. For every single board I have to figure out anew, so confusion is a purely transitive curse

andrewmcwatters3• 2 years ago

It's not that it defeated you, it's literally undocumented what you're supposed to do.

bradley13• 2 years ago

Complexity, indeed. I haven't looked into this stuff in literally decades, but: I thought the purpose of a boot loader was to pass control to code belonging to the OS - which would then be responsible for loading it's own drivers, etc.. This solution sounds like starting an entire OS, only to boot the next OS.

But then I think UEFI is also stupidly complicated, and ought to be whacked down to its core functions. Dinosaur, am I.

ziml773• 2 years ago

I like that UEFI means I don't have to worry about bootloaders clobbering each other when multiple operating systems are installed on the same drive. They can all register into UEFI, rather than competing for the MBR.

benwaffle2• 2 years ago

Install arch with a couple of different bootloaders and disk layouts, and you'll learn it all. The simplest option is potentially systemd-boot + an unencrypted rootfs.

ars• 2 years ago

The simplest is LILO without an initrd

rcxdude10• 2 years ago

Honestly I'm surprised grub is still going post-UEFI. It's now pretty much entirely unnecessary. Your simplest path is probably UEFI-stub, where there is no extra bootloader, just your BIOS loads the kernel. The main disadvantage is this is subject to the whims of your hardware manufacturer to implement it in a usable manner. If you want a nicer menu then systemd-boot is your next simplest option (despite the name, it is actually more or less seperate from systemd apart from maintenance and systemd having some integration with it).

linuxrebe1• 2 years ago

I'm curious if they're proposal will be capable of handling multi-os boots. I know grub can, I can have Linux and windows and possibly even a third OS if I want. I am concerned that red hats solution the well-intended, may be rather myopic, and be commercial only. What I failed to understand, is what problem this solves for systems that I probably only reboot once or twice a year. (Given that it only works with Linux only systems)

FredFS456• 2 years ago

You can switch OS's using the UEFI menu instead. It's not always convenient, depending on your UEFI implementation, however.

ack_complete2• 2 years ago

Yeah, look at Windows 10 if you want to see how this can be done poorly. Its boot menu works by booting Windows 10 first and then restarting the computer if you choose another OS. This includes going all the way through POST again. Took something like two minutes end-to-end to get to Windows 7.

zamadatix2• 2 years ago

I'm not sure I experienced the same with the Windows boot loader so maybe that behavior was something case specific instead of intended?

bootsmann• 2 years ago

The issue it solves, according to the talk, is that grub presents a fairly big attack surface for something that is sparsely maintained and that could be done in the kernel, which has a lot of active devs.

Shorel2• 2 years ago

Kudos to the developers involved in this functionality.

Faster boot times and more secure installations are always advantageous. I'm all rooting for this development.

I've been wondering for a while why grub is still used, given that its basic architecture is outdated.

shadowgovt• 2 years ago

I believe the two main reasons are

- inertia (don't rewrite something if it works; who really wants to own responsibility for testing this thing on all architectures GRUB currently supports?)

- multi-OS boot scenarios (I assume this new system will support that, but (a) I don't know for sure and (b) I don't really want to boot all the way into Linux just to throw Linux away and boot something else...)

saltcured• 2 years ago

This reminds me of MILO for booting Linux on some (?) DEC Alpha systems back in the 90s. I don't remember much about the actual firmware anymore. Much like today with UEFI, the system had some low-level UI and built-in drivers to support diagnostics, disk and network booting, etc.

MILO could be installed as a boot entry in the firmware-level boot menu. MILO was a sort of stripped down Linux kernel that used its drivers to find and load the real kernel, ending with a kexec to hand over the system.

No matter how you slice it, I think you'll always come around to wanting this sort of intermediate bootloader that has a different software maintenance lifecycle from the actual kernel. It is a fine idea to reuse the same codebase and get all the breadth of drivers and capabilities, but you want the bootloader to have a very "stability" focused release cycle so it is highly repeatable.

And, I think you want a data-driven, menu/config layer to make it easy to add new kernels and allow rollback to prior kernels at runtime. I hope we don't see people eventually trying to push Android-style UX onto regular Linux computers, i.e. where the bootloader is mostly hidden and the kernel treated as if it is firmware, with at most some A/B boot selection option.

lagniappe• 2 years ago

I remember LILO LInux LOader

slackfan• 2 years ago

LILO is still perfectly functional. Works great with my slackware install on my workstation.

fsniper• 2 years ago

I was about to discuss/joke about the possibility of systemd absorbing this project. And hold and behold turns out there is already systemd-boot project competing in this space. I was not aware of that at all.

Spivak• 2 years ago

systemd-boot is actually pretty great. If you're looking for a lean fast (multi-os) uefi bootloader systemd-boot is much easier to set up and less fiddly than grub. I haven't reached for grub in years.

zamadatix2• 2 years ago

I nearly did systemd-boot last install but grub2 behaves better if the motherboard is upgraded/otherwise factory reset so I shied away.

Arnavion7• 2 years ago

systemd-boot can be compiled and used independently of the booted OS using systemd. It also started out as gummiboot, unrelated to systemd.

andrewmcwatters3• 2 years ago

The Linux kernel is pretty easy to compile[1], but the first-party documentation for getting Linux to boot is total garbage. It's embarrassingly bad.

You end up reading third-party articles to figure out what the modern approach is to building your own Linux-based operating system, but even then, it's effectively undocumented how you're supposed to get out of a RAM fs from a ISO boot. You're on your own.

I completely reject the premise that Linux From Scratch is the way to do things, as walking through those steps, it's clear there are completely arbitrary steps thrown in, and as a result, it's basically its own distribution.

What I'd like to see is official documentation for:

     + Building Linux (exists)
     - Creating an initramfs image (conflicting resources)
     - Making a bootable image (conflicting resources)
     - Installing the bootloader and Linux to a target disk (no resources available)

You can do the first three easily if you know exactly the right magic incantations, and use GRUB, but then you're once again on your own.

Once you've built Linux, the experience is you get to hold it in your hand and go "this is worthless."

The Linux documentation flips between recommending initramfs and not, and also pointing you to documentation that is so old it's completely irrelevant and should be removed from kernel.org.

I am never surprised the Linux desktop experience has been bad for decades, because no one cares about creating a decent installer process to begin with. You fail right out of the gate, and it makes the entire Linux bazar experience look like amateur hack hour.

[1] https://github.com/andrewmcwatters/linux-workflow/blob/main/...

rcxdude10• 2 years ago

What is your actual need here? You talk about confusing documentation for a low-level process which basically no user is expected to go through if they aren't exploring the foundations of a linux system, or a developer working on their own distribution, and then complain that this is a lack of "a decent installer process".

andrewmcwatters3• 2 years ago

It’s in the post, can’t you read? Also, something being low-level has nothing to do with documentation.

voltagex_• 2 years ago

I'll bite.

Official documentation from who? For which audience? For which use case?

Making a bootable image for what kind of system? My Ryzen PC needs a very different image to my aarch64 router.

Where have you not seen info on "installing a bootloader to a target disk"? This is what every distro installer does - this can range from putting a kernel in an EFI partition and setting a variable to building a uboot image and setting variables in NVRAM

Lastly, what do you class as a "decent installer process"? Things have moved on from Slackware's installer. You've got everything from the Debian installer (which hasn't changed much) to Anaconda (let's run the install UI in a browser) to Ubuntu Server (everything is a container!) and many things in between.

yjftsjthsd-h5• 2 years ago

This kinda sounds like zfsbootmenu but without the ZFS. Which makes me wonder how hard it would be to factor out the ZFS bits and just use zfsbootmenu on other filesystems.

E39M5S624• 2 years ago

It'd be doable, but not with out a whole lot of hacking on it. The internals of ZFSBootMenu are tied very tightly to ZFS. Though at that point you'd largely be reimplementing https://github.com/open-power/petitboot - which probably would be easier to port to x86_64 as an EFI application.

samsartor• 2 years ago

My previous laptop was a Chromebook running Linux+Coreboot. Unfortunately the usual Tianocore UEFI BIOS people use had some bugs in the nvme and keyboard drivers, which I gave up fixing or working around (at the time). Obviously Linux had working drivers because that's all ChromeOS is, so we setup a minimal Linux install as the Coreboot payload in the firmware flash, and I wrote a little Rust TUI to mount all visible partitions and kexec anything that looked like a kernel image. It worked like a charm and had all kinds of cool features, like wifi and a proper terminal for debugging in the BIOS! Based on that experience I don't see any reason why we don't just use Linux direct instead for everything. Why duplicate all the drivers?

The code is here although it hasn't been touched it years: https://gitlab.com/samsartor/alamode-boot

jmb99• 2 years ago

I don't see any reason why we don't just use Linux direct instead for everything.

Because that would only allow you to boot Linux kernels. One of the benefits of bootloaders is the ability to boot other OSs. You can’t kexec windows.

benstoltz2• 2 years ago

You can kexec Windows: https://www.platformsecuritysummit.com/2019/speaker/koch/PSE...

2019842• 2 years ago

What's the point of using this over plain EFISTUB? I use it with Arch, and whenever I want to boot to Windows, I just use the BIOS menu. I don't see what benefit a Linux-based bootloader provides.

_ache_• 2 years ago

I do the same. The only advantage I can think of is editing kernel boot option on boot.

account4211• 2 years ago

If your EFI isn't shit you should be able to use the EFI shell to launch the kernel with whatever commandline you want.

pzmarzly• 2 years ago

EFISTUB requires recompiling the kernel every time initramfs, microcode or commandline change, no? That would get annoying pretty quickly on desktop PCs, which are not that fast with recompiling, and would need to do all of this quite often, e.g. on nvidia driver updates.

2019842• 2 years ago

I've never once had to recompile the kernel on my laptop for any reason. The kernel command line is set in the bios entry, which is somewhat tedious to change, but that's just an efibootmgr command. Initramfs gets rebuilt by pacman on larger updates, but that would happen no matter what bootloader I use.

LoganDark2• 2 years ago

The command line can be part of the UEFI boot entry depending on your particular firmware.

I think I can recompile the Linux kernel in around 15 minutes, but I have a 12400F. And 15 minutes is still 60 times longer than most people are willing to wait.

mjg5918• 2 years ago

UKIs provide mechanisms for adding additional sidecar modules which can extend the initramfs, provide additional command line modifications, and so on.

Delk• 2 years ago

Entering the BIOS menu takes several seconds on my ThinkPad, and getting to the EFI boot menu from there takes a few more. That's after hitting the key during the correct time during the boot process, which sometimes takes guessing.

In principle, the EFI multiboot mechanism should be the way to handle basic multiboot options. It would of course be nicer and cleaner from a design perspective not to have redundant mechanisms on top of each other. In practice, though, using the EFI boot menu can be clumsy. The real solution would be for it to not be clumsy but it doesn't look like we're necessarily there.

zamalek• 2 years ago

This is a porcelain for EFISTUB alongside other existing things.

jansommer• 2 years ago

Not that I would want to dual boot on my 64 gb surface go 2, but if I did, I'd need a bootloader with a menu, because there isn't one in the bios.

lofaszvanitt7• 2 years ago

Also create a boot please that rivals w10's almost instant boot process. I just hate the current slow/non parallel boot process.

bayindirh5• 2 years ago

Many of our systems boot under 10 seconds after GRUB. You can make GRUB menu to timeout quickly or be completely hidden if you want.

A modern system with a connected network can boot quite fast. Windows' instant boot is not boot actually, it's thawing hibernation.

One of the biggest features touted by systemd is "embarrassingly parallel" booting capabilities, which Parallel SYS-V already sported.

IOW, Linux already can boot pretty quickly given no hardware device is holding it back.

lofaszvanitt7• 2 years ago

Not fast enough.

dvhh2• 2 years ago

As you might know windows is kind of cheating with the "instant boot" by creating an hibernate snapshot of the OS before login.

Otherwise, I while I would not describe the boot process of most of the linux I own as "instant" they are certainly booting quite faster that windows.

lofaszvanitt7• 2 years ago

Didn't know that one, thanks.

Animats2• 2 years ago

Or, really, use the ROM's boot loader.

This is getting closer to the way QNX booted decades ago. The boot image has the kernel and whatever user space programs and .so files you decide to include. For a deeply embedded system, you might not have a file system or networking. For desktop QNX (discontinued), you'd have some disk drivers, a file system driver, a network driver, and a shell, along with a startup script, to get things going.

bregma• 2 years ago

QNX still works that way. It's just no longer free.

Animats2• 2 years ago

And the desktop environment is gone.

alerighi• 2 years ago

It's something you can do since a lot of years. I used to do so 10 years ago, when I've got the first motherboard with UEFI. But is it useful? It saves a minimal time in the boot sequence, but at what cost?

The bootloader (being it grub, or something more simple as systemd-boot) is useful to me for a couple of reasons:

- it allows to dual-boot with Windows easily: motherboard boot menu is often not easy to access, you need to perform some key combination in a short window, also modern bootloader save the last boot option such that if Windows reboots for an update Linux does not start

- it allows to edit the cmdline of the kernel to recover a system that does not boot, e.g. start in single user mode. That can really save your day if you don't have on hand an USB stick and another PC to flash it

- it allows you to choose between multiple kernels and initrd images easily, again for recovery purposes

- it has a voice for entering the UEFI setup menu: in most modern systems again entering the UEFI with a keyboard combination is unnecessarily difficult and has a too short timeout

- it allows you to boot any other EFI application, such as memtest, or efi shell. Most UEFI firmwares doesn't have a menu to do so.

ec1096852• 2 years ago

Just because the boot loader is using Linux, it doesn’t prevent an alternative OS from being booted into, so there is nothing fundamentally stopping all of grub’s features from working in this new scheme.

jchw4• 2 years ago

It is a bit more complex, though. Quoting "nmbl: we don’t need a bootloader" from last month[1]:

- Possibility to chainload from Linux while using Secure / Trusted boot: Dual-booting, although not supported on RHEL, is important for Fedora. While there are attempts to kexec any PE binary, our plan is to set BootNext and then reset, which will preserve the chain of trust that originates in firmware, while not interfering with other bootloaders.

It could be seen as an advantage to do chainloading by setting BootNext and resetting. I think Windows even does this now. However, it certainly is a different approach with more moving parts (e.g. the firmware has to not interfere or do anything stupid, harder than you'd hope) and it's definitely slower. It'd be ideal if both options were on the table (being able to `kexec` arbitrary UEFI PE binaries) but I can't imagine kexec'ing random UEFI binaries will ever be ideal. It took long enough to really feel like kexec'ing other Linux kernels was somewhat reliable.

[1] https://fizuxchyk.wordpress.com/2024/06/13/nmbl-we-dont-need...

nerdponx• 2 years ago

rEFInd is the magic tool here.

Personally I still use GRUB for all of the reasons you stated above. But rEFInd + kernel gets you pretty close.

zekica• 2 years ago

rEFInd is great! I wish they just updated the default theme to something nicer.

smeg_it• 2 years ago

I've used gummiboot before systemd ate it; and I've used rEFInd. Mainly, I just followed the excellent documentation @ https://www.rodsbooks.com/; that's also how I first familiarized myself with UEFI (Thanks Rod!).

My brain has leaked all the information I understood (unfortunately). Is rEFInd still active? Is there a gummiboot fork (besides systemd)?

Personally, I kind of hate Redhat calling itself that now, it's IBM. You can tell because all of the online knowledge from the community on their websites are now pay-walled. RIP Redhat (CentOS) (I'll miss you)

P.S. Thanks Rocky Linux (and others like it)

throwway120385• 2 years ago

If you embed an x86 system somewhere then you might find yourself not wanting to use GRUB because you don't want to display any boot options anywhere other than the Linux kernel. The EFI stub is really handy for this use case. And on platforms where UBoot is common UBoot supports EFI which makes GRUB superfluous in those cases.

Many of the Linux systems I support don't have displays and EFI is supported through UBoot. In those cases you're using a character-based console of some sort like RS232.

A lot of those GRUB options could also be solved by embedding a simple pre-boot system in an initial ramdisk to display options, which maintains all of the advantages of not using GRUB and also gives you the ability to make your boot selection. The only thing GRUB is doing here is allowing you to select which kernel to chain-load, and you can probably do the same thing in initramfs too through some kind of kernel API that is disabled after pivot root.

Sesse__• 2 years ago

I must admit that on U-Boot platforms, I use U-Boot EFI to load grub-efi, so that I can have a non-terrible bootloader…

cool_beanz4• 2 years ago

I just have two kernels with two boot options in BIOS. I just hit F11 at boot time and choose a BIOS boot option for either kernel. Of-course, you need to add the entries in UEFI, either from UEFI shell either with some tool (efibootmgr). This scheme also supports secure booting and silent booting. The stubs are signed after being generated.

Denvercoder92• 2 years ago

What kind of machines are people using that entering the UEFI boot menu is difficult? On all three of mine I just press F10 during the first 5 or seconds the vendor logo shows, and I end up in a nice menu where I could select Windows, other kernels, memtest, or the EFI shell or setup.

mjg5918• 2 years ago

One easy way to meet Microsoft's boot time requirements is to skip input device enumeration, so there's a lot of machines meeting the Windows sticker requirements where entering the firmware either requires a bunch of failed boots or getting far enough into the boot process that you can be offered an opportunity to reboot into the setup menu.

pavon• 2 years ago

I was working on my Dad's Dell laptop this weekend, and no matter how quickly I spammed the correct key (F12 in this case) it would miss it and continue to a full boot about 3/4 times. I never figured out if it is just picky about timing, or if it had different types of reboots where some of them entering BIOS wasn't even an option.

spockz• 2 years ago

On my last two uefi boards, if I press F12 or F8 too soon after power on it either stalls the boot, or it makes it restart. When the latter happens, I’m always too careful in pressing it causing me to miss the window of opportunity and booting right to the OS. Entering the bios or choosing the boot drive regularly takes me 3 tries. (Gigabyte with Intel and Asus with AMD.)

Am4TIfIsER0ppos• 2 years ago

Grub is the same everywhere. Motherboard bios/uefi is not. It isn't F10 for me.

yjftsjthsd-h5• 2 years ago

If I'm understanding correctly, it might help to point out that in spite of the title they are proposing a bootloader, which can still let you modify the cmdline, boot to other OSs, etc. It's just that the bootloader is itself using the Linux kernel so it can do things like read all Linux filesystems for "free" without having to rewrite filesystem drivers.

garaetjjte3• 2 years ago

It could kexec other kernels but probably won't be able to jump to other OS bootloaders after it already called ExitBootServices.

kragen4• 2 years ago

you seem to be saying that they are using two separate kernels, one for the bootloader and one for the final boot target

the title text says 'Loaded by the EFI stub on UEFI, and packed into a unified kernel image (UKI), the kernel, initramfs, and kernel command line, contain everything they need to reach the final boot target' which sounds like they're not talking about using two separate kernels, one for the bootloader and one for the final boot target, but rather only one single kernel. possibly that is not the case because the actual information is hidden in a video i haven't watched

https://news.ycombinator.com/item?id=40909165 seems to confirm that they are indeed not saying what you thought

edit: they're proposing both configurations

cool_beanz4• 2 years ago

You can have command line parameters baked into the EFISTUB. I also have two kernels, so there's two UKIs on /efi, and I have both added as separate boot options in BIOS.

zozbot234• 2 years ago

- it allows to edit the cmdline of the kernel to recover a system that does not boot, e.g. start in single user mode. That can really save your day if you don't have on hand an USB stick and another PC to flash it

You can use the UEFI shell for this. It's kind of a replacement for the old MS-DOG command line.

Dalewyn• 2 years ago

it allows to dual-boot with Windows easily

Windows Boot Manager can chainload into any arbitrary bit of code if you point it where it needs to hand off.

It's a feature that goes back to Windows NT (NTLDR) supporting dual boot for Windows 9x, but it can be repurposed to boot anything you would like so long as it can execute on its own merit.

eg: Boot into Windows Boot Manager and, instead of booting Windows, it can hand off control to GRUB or systemd-boot to boot Linux.

fuzzfactor4• 2 years ago

Windows Boot Manager can chainload into any arbitrary bit of code if you point it where it needs to hand off.

With the NT6 bootloader this appears to be limited to operating only in BIOS mode using bootmgr.exe. The traditional chainloading is still possible by pointing to a binary file which is a copy of a valid partition bootsector, whether it is a Microsoft bootsector or not.

The equalent BCD for UEFI mode uses bootmgr.efi (instead of bootmgr.exe), and does not seem to be capable of chainloading even when there is an equivalent BOOTSECTOR bootentry on the NT6 multiboot menu.

It would be good to see an example of the NT6 bootloader successfully handling UEFI multibooting which includes starting Linux from the EXTx partition it is installed on. Still works perfectly in BIOS since early NT, but in UEFI not so much.

1vuio0pswjnm72• 2 years ago

As much as I generally detest indirection, for me a bootloader is a necessity; I need the flexibity to boot different OS kernels. AFAIK, UEFI offers no such flexibility. NetBSD's bootloader is best for me. UEFI seems like an OS unto itself. A command line, some utilties and network connectivity (UNIX-like textmode environment) is, with few exceptions, 100% of what I need from a computer. To me, UEFI seems potentially quite useful. But not as a replacement for a bootloader.

sholladay• 2 years ago

I need the flexibity to boot different OS kernels. AFAIK, UEFI offers no such flexibility.

Isn’t this how Apple’s Bootcamp works (at least on Intel based Macs)?

cool_beanz4• 2 years ago

I need the flexibity to boot different OS kernels. AFAIK, UEFI offers no such flexibility.

Yes it does, I use it with two kernels, just have different entry for each stub in UEFI. Whenever I want to boot the non-default kernel I just hit F11 (for BIOS boot menu, on my motherboard) and choose the boot option. You just need to add the boot options in UEFI, pointing to the corresponding EFI files. They also have the kernel command line parameters baked into them and you can set your desired ones (silent boot whatever).

ziml773• 2 years ago

Does Windows not ensure that the UEFI boots back into Windows when it does an auto-reboot for updates? There's a UEFI variable called BootNext which Windows already knows how to use since the advanced startup options must be setting it to allow rebooting directly to the UEFI settings.

Given that Windows tries to restore open windows to make it look like it didn't even reboot, I'm surprised they wouldn't make sure that the reboot actually goes back into Windows.

joe5150• 2 years ago

Not in my experience. For my typical dual boot situation where Grub is installed as the bootloader, I have to update the Grub settings like so to allow Windows updates to go smoothly:

  GRUB_DEFAULT=saved
  GRUB_SAVEDEFAULT=true

ale424• 2 years ago

No, it doesn't. Even a sysprepped image of Windows (which thus runs Setup to install drivers and finalize the installation) doesn't change the boot order on UEFI machines. I think just the installer does this when you first install Windows.

29athrowaway• 2 years ago

I need a bootloader that automatically deletes Windows partitions upon detection.

And is also themed like XBill.

radium3d• 2 years ago

I dual boot Win/Arch easily with EFISTUB setup. It's super quick to boot to a usb stick of arch if I need to edit anything with the configuration in an "emergency" situation as well. https://wiki.archlinux.org/title/EFISTUB

eru• 2 years ago

You left out the most important reason I went back to using grub: some motherboards have dodgy UEFI support, and having an extra layer of indirection seems to be more robust sometime for some reason.

Timber-6539• 2 years ago

- it allows to edit the cmdline of the kernel to recover a system that does not boot, e.g. start in single user mode. That can really save your day if you don't have on hand an USB stick and another PC to flash it

This is an indication of bad admin choice. The kernel defaults should not corrupt the boot process and if you add further experimental flags for testing you ought to have a recovery mechanism in place beforehand.

herewulf• 2 years ago

It allows you to enter your passphrase to unlock your Linux LUKS partition before you even get a menu to chainload Windows.

At least this is what an Arch Linux derivative (Artix) system of mine does, amusingly. It sort of gives an observer the impression that it's an encrypted Windows system on boot.

account4211• 2 years ago

it allows to dual-boot with Windows easily: motherboard boot menu is often not easy to access, you need to perform some key combination in a short window

Hardly a problem in my experience - just hold down the key while booting.

And dual booting is rarely needed anyway and generally just a pita. Just always boot into your preferred OS and virtualize the other one when you really need it.

also modern bootloader save the last boot option such that if Windows reboots for an update Linux does not start

You can change the EFI boot entries including priority from the OS, e.g. via efibootmgr under Linux. Should be easy to setup each OS to make itself the default on boot if that's really what you want.

it allows to edit the cmdline of the kernel to recover a system that does not boot, e.g. start in single user mode. That can really save your day if you don't have on hand an USB stick and another PC to flash it

All motherboards I have used had an EFI shell that you can use to run EFI programs such as the Linux kernel with efistub with whatever command-line options you want.

it allows you to choose between multiple kernels and initrd images easily, again for recovery purposes

EFI can have many boot entries too.

it has a voice for entering the UEFI setup menu

What does "a voice" here mean? Or you meant "a choice"? Either way, same as with the boot menu you can just hold down the key while booting IME.

it allows you to boot any other EFI application, such as memtest, or efi shell. Most UEFI firmwares doesn't have a menu to do so.

In my experience the EFI shell has always been accessible without a bootloader.

littlecranky672• 2 years ago

And dual booting is rarely needed anyway and generally just a pita. Just always boot into your preferred OS and virtualize the other one when you really need it.

I've been dual-booting linux since the kernel 2.2.x era and being able to do it was a major driver to migrate away from windows. It is super important for onboarding of new users that can't yet get rid of windows fully - mostly because of gaming (yes proton is nice, but anything competive that uses anti-cheat won't work yet is the majority share of gaming). And that is the reason I still boot into Windows on my dual-boot machine: Gaming. For me that windows is just a glorified bootloader into GoG or Steam, yet desperately needed and virtualization won't solve anything here.

myworkinisgood• 2 years ago

I have experience with two different laptops: 1. Dell enterprise laptops generally have a robust EFI system which allows for all kinds of `.efi` files to boot on `vfat` partitions. Dell laptops also have a good firmware setup for stuff like mokutils to work so that people can use measured boot with their own version of linux. They also work extremely well with self-encrypting nvme drives. 2. HP consumer laptops which are the worst of lot and essentially prevent you from doing anything apart from stock configurations, almost like on purpose. 3. All other laptops which have various levels of incompetence but seems pretty harmless.

For all laptops apart from Dell, Grub is the bootloader that EFI could never be.

prmoustache14• 2 years ago

- it allows to dual-boot with Windows easily: motherboard boot menu is often not easy to access, you need to perform some key combination in a short window, also modern bootloader save the last boot option such that if Windows reboots for an update Linux does not start

Do people really dual boot a lot in 2024? It was a good use case when virtualization was slow but decades after the CPU started shipping with virtualization extensions there is virtually zero overhead in using VM nowadays and it is much more convenient than rebooting and losing all your open applications just to start one on another OS.

- it allows you to boot any other EFI application, such as memtest, or efi shell. Most UEFI firmwares doesn't have a menu to do so.

How many times in a decade are you running memtest?

Getting to UEFI firmware or booting another OS/drive is just a matter of holding one key on my thinkpad. I would just simply not buy and bad hardware that doesn't allow me to do that. Vote with you wallet damit.

I would also argue that you can perfectly have grub sitting alongside a direct boot to kernel in an UEFI setup. There are many other bootloaders than grub and users are still free to use them instead of what the distro is shipping. UEFI basically allows you to have as many bootloader as you have space on that small fat partition.

messe• 2 years ago

Do people really dual boot a lot in 2024?

Yes, there are still use cases for it.

The state of GPU virtualisation, for example, is a spectrum from doesn't exist/sucks to only affordable for enterprise customers.

So unless you have a second graphics card to do pass through with, if you want to use your GPU under both OSes then you almost always have to dual boot (yes, there are other options like running Linux headless, but it's not even remotely easier to set up than dual boot)

zik• 2 years ago

Do people really dual boot a lot in 2024?

Yes. I work on Linux and play most games on Windows. Playing games on a VM is... pretty terrible.

adham-omran• 2 years ago

Do people really dual boot a lot in 2024?

Yes.

there is virtually zero overhead in using VM nowadays

Not for real-time audio production. The state of audio plugins having Linux support from vendors like EastWest, Spitfire, Native Instruments, iZotope is abysmal and even Wine does not run them nowadays.

Even with a virtual machine that has pinned cores and USB pass-through of a dedicated audio interface, it practically locks you to one sample rate, any change causes crackles, try to load more than one plugin and you hear crackles. There is plenty of overhead.

drtgh• 2 years ago

Do people really dual boot a lot in 2024?

One of the big problems is with the graphics cards, because the vendors block a driver functionality ( SR-IOV ) for consumer GPUs that would allow single GPU passthrough for VMs.

The alternative is to leave the system headless (reboot needed, and the VM need to run as root), or to use two graphics cards (wasting power, hardware resources, etc.), for which you also need to add an extra delay layer inside the VM for to re-send the graphics back to the screen, or to connect two wire inputs to the monitor.

tengwar2• 2 years ago

Yes, people dual boot. Particularly people who are contemplating a move from Windows. I'd hate to see Linux take the "my way or the highway" attitude of Windows.

blincoln• 2 years ago

I dual-boot on my personal desktop. I mostly use Debian, but there's a Windows partition for games and a few other Windows-specific things. The GPU in it was way too expensive to justify buying two, and I use it under Linux for ML, hash-cracking, etc.

My original plan was to do everything in a Windows VM, but there was too much of a performance hit for some of my purposes, and VMWare doesn't allow attaching physical disks or non-encrypted VMDKs to a Windows 11 VM, so it's actually easier to have a data drive that's accessible from both OSes with dual boot than it would be with a VM.[1] I'm still disappointed about that.

[1] Using HGFS to map a host path through to the VM is not an option because of how slow that is, especially when accessing large numbers of files.

michaelmrose6• 2 years ago

Do people really dual boot a lot in 2024

Seems the answer is yes. https://linux-hardware.org/?view=os_dual_boot_win

there is virtually zero overhead in using VM nowadays

It might be more accurate to say that if you have a fast computer with lots of resources the experience running a basic desktop experience feels perceptibly native. This means it is a great answer to running windows software that neither needs a discrete GPU nor direct access to hardware on the minority of machines that are capable enough for this to be comfortable.

In actuality laptops are more common than desktops and the majority of computers have 8GB of RAM or less. 60% all form factors 66% laptops. This just isn't enough to comfortably run both.

https://linux-hardware.org/?view=memory_size&formfactor=all

Furthermore while most Linux users are comfortable installing and running windows and Linux whereas they may or may not be familiar with virtualization.

Also probably the number one reason someone might dual boot is probably still gaming which although light years ahead of years prior still doesn't have 100% compatibility with Windows. In theory GPU passthrough is an option but in reality this is a complicated niche configuration unsuitable for the majority of use cases. Anyone who isn't happy with steam/proton/wine is probably more apt to dual boot rather than virtualize.

notorandit• 2 years ago

Maybe it is time to re-think the entire hardware boot process and ditch the BIOS altogether.

lproven12• 2 years ago

It probably was, but UEFI was not a good answer.

I'd have preferred CoreBoot or OpenFirmware, but the PC industry was too slow to move and let Intel -- still smarting from Microsoft forcing it to adopt AMD's 64-bit x86 extensions -- take control of the firmware.

dheera• 2 years ago

it allows to edit the cmdline of the kernel to recover a system

Except they've made it increasingly harder to do this over the years. Nowadays you have to guess when it is on the magic 1 second of "GRUB time" before it starts loading and then smack all the F keys and ESC key and DEL key at the same time with both hands and both feet because there is nothing on the screen that tells you which key it actually is.

All while your monitor blanks out for 3 seconds trying to figure out what HDMI mode it is using, hoping that after those 3 seconds are over that you smacked the right key at the right time.

And then you accidentally get into the BIOS instead of the GRUB.

It used to be a nice long 10 seconds with a selection menu and clearly indicated keyboard shortcuts at the bottom, and you could press ENTER to skip the 10 second delay. That was a much better experience. If you're in front of the computer and care about boot time, you hit enter. If you're not in front of the computer, the 10 seconds don't matter.

I know you can add the delay back, I just wish the defaults were better.

markandrewj• 2 years ago

It is bold of RedHat to claim this is 'their solution'. UEFI has already been used for years to boot without grub. Some examples, MacOS, HP-UX, or systemd-boot via UEFI.

michaelmrose6• 2 years ago

The suggested system would use bootnext to allow you to boot to windows. You could also put something in front of it like reEFInd

bastien2• 2 years ago

Except that doesn't work in the real world, where encrypted and authenticated boot disks are increasingly common.

So you'll need a significant amount of code that isn't the permanently-resident kernel that has enough device support to access keys and decrypt and authenticate what holds the kernel that will launch the OS.

IOW, you'll just have to reinvent a bootloader anyway.

Or you can address the problems with GRUB, extend it to do what you need, and avoid doing the traditional linux folly of Yet Another Unnecessary Reinvention.

Or was systemd vendor lock-in not enough for your shareholders?

ec1096852• 2 years ago

Isn’t their argument that much of this code already exists in Linux?

mjg5918• 2 years ago

The EFI system partition is, by definition, either not encrypted or is unlocked by the firmware - your bootloader wouldn't work otherwise. In this setup, you just stick the UKI on the EFI system partition, and unlocking the rest of the drive is performed in the initramfs.

rcxdude10• 2 years ago

This code already exists in UEFI in the form of secure boot. The 'bootloader' (more accurately 'boot menu' IMO) kernel and its initramfs would be authenticated and unlocked by the system firmware, and then authenticate and unlock the rootfs and (optionally) different kernel for that system. It's basically going "hey, GRUB is more or less re-inventing the linux kernel, why don't we just write a simple userland for linux that does the same job but with way less code instead?"

BobbyTables2• 2 years ago

Actually I don’t think UEFI firmware validates the initramfs — that is loaded by the kernel’s efi stub.

One can make a UKI image which glues the two together in a single file along with a tiny bit of code for booting it.

michaelt• 2 years ago

Ah yes, unified kernel images.

Finally, an end to the tiresome and obsolete notion of Linux running modified versions of the Linux kernel. With unified kernel images, Linux users can finally be confident knowing their kernels are signed by companies with Microsoft's blessing, such as Red Hat and Canonical - and Linux will be have proper support for the use cases of companies like TiVo, who want to run Linux, but also want to ensure the device owner can't make any modifications to the software on their device.

This will be well worth it, to protect against the ever present issue of criminals breaking into my hotel room, finding my unattended laptop, and deciding not to steal it to sell on ebay - but instead to secretly modify my initramfs. I don't know about you, but I've had two covert CIA teams rappel in through my window this week alone.

mjg5918• 2 years ago

Any signature on a UKI is only relevant if you have secure boot enabled, and if you have secure boot enabled using the generally trusted keys then you're already not able to boot unsigned kernels. If you want to run arbitrary kernels then either use keys under your control (which UKIs support) or turn off secure boot - UKIs change absolutely nothing here.

cbarrick• 2 years ago

I developed a tool for managing EFI boot entries for my personal use.

I've been meaning to get it ready to release publicly. It's mostly there, just a bit manual to install.

https://efiboot.cbarrick.dev

peter_d_sherman4• 2 years ago

"Although GRUB is quite versatile and capable, its features create complexity that is difficult to maintain, and that both duplicate and lag behind the Linux kernel while also creating numerous security holes."

We agree thus far -- that GRUB may create unnecessary complexity and security holes (Note the relationship between "complexity" and "security holes" -- where you find one, you will usually find the other... they're intertwined like Yin and Yang -- you usually don't get one aspect alone by itself -- without also getting the other...)...

"Loaded by the EFI stub on UEFI"

"Er, begging the question Governor" but isn't EFI and UEFI also a bootloader?

Aren't those systems also complex?

I think the article is trying to make the point that a small EFI stub program which loads a larger program, in this case, a modified version of the Linux Kernel itself could easily be audited for security issues, and yes, that's sort of true -- but remember that the EFI loader, no matter how small, still has to run in the UEFI environment, and the entire UEFI environment is anything but not complex...

Phrased another way, running a tiny open source, secure program on a gigantic, complex black-box VM with many undocumented/opaqued/"black box" parts -- may not be all that secure...

Still, any small part of a system that could be made simpler despite there being other obscure "black box" undocumented or poorly documented complex components at play -- is definitely a step in the right direction towards full future transparency and auditability...

mjg5918• 2 years ago

The UEFI environment is a given, unless you're in a position to replace the firmware - using grub doesn't avoid it in any way. But for the most part the security properties of the underlying firmware don't matter that much if the attack surface it exposes can only be touched by trusted code, which is the case if secure boot is enabled (and if secure boot isn't enabled then there's no real reason to bother attacking the firmware, you can already just replace the OS)

peter_d_sherman4• 2 years ago

The UEFI environment does not exist on older PC's.

UEFI started to become mainstream around 2013 -- that is, an increasing amount of PC motherboard manufacturers started to put it on motherboards (rather than the older BIOS) around this time.

It should be pointed out that on some motherboards the UEFI software may be placed on an IC (EPROM, EEPROM (Electrically Erasable Programmable Memory), Flash, NVRAM, ?) -- which may be writable, or writable under certain conditions (i.e., if the boot process doesn't load software which explcitly blocks this when the system starts up, or if such blocks, once existing, are bypassed, by whatever method...)

If the UEFI-storing IC is writable (or that IC replaceable, either via socket or solder), then the UEFI (again, under the proper conditions) is subject to modification then it is modifyable; changeable; updatable, programmable; etc. etc.; use whatever linguistics you deem appropriate...

"The UEFI environment is a given, unless you're in a position to replace the firmware"

If what I've written above is the case -- then any such UEFI envrionment (aka "firmware") under such conditions is very much replaceable!

And if it is replaceable, then that firmware code can be made simpler by somone "rolling their own" -- and replacing it!

Now that I think about it, I'm going to have to do more research for the next motherboard I buy... if it has to have UEFI on it, if I am compelled to buy a UEFI motherboard, then I want that UEFI firmware to be overwriteable/customizable/modifyable/auditable -- by me!

Also -- I'd never trust "trusted" code implicitly...

Didn't Ronald Reagan so eloquently say "Trust -- but verify?"

It's the but verify part -- that's key!

Anytime a security vendor or vendor (or any authority or "authority" for that matter) tells me to trust or "trust" something, my counterquestion is simply as follows:

"Where is the proof that the thing asking for my trust is indeed trustworthy?"

In other words,

"How do I prove that trust to myself?"

In other words,

"Where is the proof?"

And let's remember that proof by analogies (Bjarne Stroustrup) and proof by polled social approval consensuses ("4 out of 5 dentists recomend Dentyne for their patients that chew gum") -- are basically fraud...

Anyway, your assessment, broadly speaking, is not wrong!

It's just that there are additional "corner cases" which require some very nuanced understandings...

https://en.wikipedia.org/wiki/Open-source_hardware

https://en.wikipedia.org/wiki/Right_to_repair

https://en.wikipedia.org/wiki/Non-volatile_memory

https://libreboot.org/

https://www.coreboot.org/

https://en.wikipedia.org/wiki/Open-source_firmware

vlovich1234• 2 years ago

I really like the idea and the approach. I’m a little concerned however about the compatibility issues with kexec. For example, here’s what Arch says about the NVidia module:

The graphics driver needs to be unloaded before a kexec, or the next kernel will not be able to gain exclusive control of the device. This is difficult to achieve manually because any programs which need exclusive control over the GPU (Xorg, display managers) must not be running. Below is an example systemd service that will unload the KMS driver right before kexec, which requires that you use systemctl kexec.

It also talks about ACPI issues and there was a question in the presentation although it was unintelligible. More generally, I could imagine more back and forward compat issues that wouldn’t arise from a simpler bootloader that is only initializing a very constrained amount of hardware whereas the kernel will try to boot the full HW twice. I hope they figure out how to make it work, but I suspect they’ll run into pretty significant challenges running this on real “legacy” HW until this is in the ecosystem enough that HW vendors will support it better. A bonus would be that kexec will become better supported and more robust over time if there’s broader adoption.

I also wonder if there’s any back/forward compat issues kexec between very different kernel versions, but I’m guessing the kexec mechanism was intentionally designed to support that as best as it can.

https://wiki.archlinux.org/title/Kexec

mjg5918• 2 years ago

There's no reason to load things like the nvidia driver if all you want to do is offer a choice to kexec into another kernel, which makes things easier - you can continue just using the display environment the firmware set up.

vlovich1234• 2 years ago

I think you’re missing the broader point I was trying to make by hyperfocusing on 1 example of an issue that can arise from kexec and is solvable in a number of ways. Ultimately the critique raised in the video about focusing on the VM and not trying this on real HW yet is a very real one and is the single hardest problem here I suspect, so punting on it can’t go on for too long.

kbolino5• 2 years ago

This is true on "IBM compatible" x86 PCs and will continue to be for the foreseeable future, but it's not the case on all platforms. Some of them require graphics drivers to show anything at all, even simple text.

raggi3• 2 years ago

you bet though that as soon as the grub types are forced into userspace they're going to want to do fancy userspace things, like give me a fancy framebuffer driver and the ability to push a shader into the gpu to animate while the second kernel stage boots, etc etc.

the more rope given here, the more will be taken, a rich programming environment of a whole kernel will I'm sure raise temptation to new levels of stuff here, and the natural progression from the shader framebuffer is hand-off to the next kernel stage so it can keep the animation going until wayland starts or whatever. maybe i'm paranoid.

AtlasBarfed• 2 years ago

Another red hat "improvement" that causes another decade plus of churn and documentation and support chaos?

unixhero• 2 years ago

Awesome, finally.

Aissen• 2 years ago

Considering distros serious about booting are effectively shipping grub forks with tens (debian) to over a hundred (ubuntu) to hundreds (fedora) of patches on top, it might be time to invest a bit more into Open Source early-stage booting. I'm doubtful that efistub + UKIs will solve all the problems, but I'm cautiously optimistic. Wait and see!

tristor• 2 years ago

I do UKIs and direct boot them on Arch. Works great. Do have to recompile for every change, but it's very fast on a modern system, takes about 40 seconds on my laptop.

benstoltz2• 2 years ago

One can trade run-time flexibility for size, speed, and small attack surface.

Taken to the limit, Oxide Computer boots using the [Pico Host Boot Loader](https://github.com/oxidecomputer/phbl) which is probably not suitable for your personal system where you would want to boot many OS images from many devices on many different mainboards using very similar or modular boot flash images.

Phbl transfers control to a partial Unix image, also in the boot flash, which brings in the rest of the OS from a well-known boot device. There is no UEFI, CoreBoot, PXE boot etc. The AMD PSP code does run, but that's the only early external blob in the boot path. This does mean that the OS has to understand its hardware, there is minimal "free" initialization.

Dwedit2• 2 years ago

You had the bootloader because first you needed executable code in the first sector of the partition, and you can't fit much in those 512 bytes. But moving to UEFI means you never execute that code anymore. Instead, you load a BOOT.EFI file off of a FAT16/FAT32 partition. If there's a restriction on size for that, then you proceed to a bootloader instead of the real kernel.

dvhh2• 2 years ago

That's for the case for MBR partition type, I really hope we moved to more modern alternatives

creshal4• 2 years ago

GPT puts no size limitations on the FAT32 EFI System Partition. Your bootloader can be as big as you want it to be, which is why just booting off of a Linux kernel image with an initrd in the same file has been a valid option for years. Not sure why Lennart feels compelled to reinvent this particular wheel again.

josephcsible3• 2 years ago

Does "security" here mean security from the computer's owner, i.e., Treacherous Computing? If not, then what kinds of security holes are even possible at the point when GRUB is running?

mjg5918• 2 years ago

grub consumes a bunch of untrusted material (splash pictures, fonts, filesystems, executables, and more) and parses them. grub's also written in C, which is pretty much the worst case for writing parsers. Someone able to replace any of these with something that triggers a vulnerability in grub is then able to, for instance, take control of your boot process and obtain your disk encryption key or user password or any other secrets you enter.

(I don't want to seem like I'm picking on grub here, it wasn't written with this threat model in mind and it does a lot of things and achieving all of this stuff securely is hard)

josephcsible3• 2 years ago

Isn't everything that GRUB reads only writable by root? Is the threat model that root is the attacker?

pmarreck• 2 years ago

No thanks. NixOS lets you pick the generation at boot via GRUB. This is extremely useful.

mjg5918• 2 years ago

A lot of the commentary here is based on misunderstandings of the capabilities and constraints of a UEFI environment and what the actual goals of this project are, and I think miss the mark to a large degree. Lennart's written some more explicit criticism at https://lwn.net/Articles/981149/ and I think that's a much more interesting set of concerns.

rcxdude10• 2 years ago

I feel like that post misses the biggest one that pulls people to GRUB: complicated boot sources and procedures. Filesystems that UEFI doesn't understand, more complex network boot sources, all that kind of complex messiness that GRUB enables and others don't. Now, whether those are good idea or not is a different question, but I think this is a good concept for a full replacement for GRUB, as opposed to the existing replacements which already cover the 90% case pretty well. (And I think it's got a case for handling the other cases OK: from the sounds of it they plan to lean on UEFI and A/B image to handle fallback, and it'll basically just work as a direct UEFI boot in the common case)

cycomanic• 2 years ago

I have to say I find Lennart's arguments quite unconvincing. As another person said, the vast majority of people just want default boot to the most recent kernel (which this proposal could do well).

But then when it comes to the other points, yes I want to be able to reliably boot into other systems, but both systemd-boot and grub are notoriously bad at detecting other systems on disks (both use install-time detection IIRC). The only one which does a reasonable job is rEFInd. But even more a kernel with appropriate drivers could even add kernels/systems on usb disks to the selections (why do I have to go to the UEFI selection to boot from USB).

The next thing he completely ignores is booting into zfs or btrfs snapshots, which is not possible using systemd-boot AFAIK, and again would be much nicer to do with a kernel.

Certhas• 2 years ago

Also, from what I understand after watching some of the video demonstration in the Q&A, I could just have another EFI entry point towards the nmbl configuration with a grub like menu, and get an exact replica of the grub experience. Having to go through the BIOS boot menu for those rare occasions where I need it is perfectly reasonable.

unaindz• 2 years ago

Not that it retracts from your argument but rEFInd can handle detecting bootable USBs afaik. It's just not enabled by default

kasabali3• 2 years ago

completely useless if you care about Measured Boot

I stopped reading there. All these engineers who help build and defend this draconian crap should be forced to used only an iPad for the rest of their lives.

tpoacher• 2 years ago

Of all the horrible punishments you could have envisioned, you went full-on "I have no mouth and I must scream" there...

mjg5918• 2 years ago

Measured boot is, in itself, under user control - you can seal whatever secrets you want to any specific state and they'll only be accessible in that situation. This has obvious benefits in terms of being able to (for instance) tie disk encryption keys to a known boot state and so avoid needing to type in a decryption phrase while still preventing anyone from being able to simply modify your boot process to obtain that secret. The largest risk around this is from remote attestation, and that's simply not something where the infrastructure exists for anyone to implement any kind of user restriction (and also it's trivial to circumvent by simply tying any remote attestation to a TPM that's not present at boot time and so can be programmed as necessary - it's just not good at being useful DRM)

rcxdude10• 2 years ago

Thinking about it a bit more, though, it does feel like a hybrid approach is probably better. For dual-booting off local disks and other simple cases, just having the kernel and initramfs alongside other OS options makes a lot of sense, and you can use the UEFI boot menu or something deliberately simple like systemd-boot to select between them for dual-boot or recovery. For more complex cases (where your rootfs is not just something the kernel can mount on its own), instead you basically just want a process for building your initramfs to do that from a config like grub (which is already how a lot of cases like that are solved, anyway), and in extreme cases where you also want to stash a kernel in some other location then you can use kexec from that. But for just a boot menu (which is aready in the minority case and 90% of users in that case need nothing more) it feels even heavier than grub for little benefit.

DEADMINCE5• 2 years ago

I have a bootloader signed with my own keys to boot my kernel. Nothing else will be able to boot the machine. I couldn't have this setup without a bootloader.

worthless-trash2• 2 years ago

You absolutely can sign the kernel with your own keys. This would allow you to boot your machine into the first level kernel without the bootloader.

Is this 'couldn't' a self imposed requirement or a technical one I can't think of ?

DEADMINCE5• 2 years ago

Is this 'couldn't' a self imposed requirement or a technical one I can't think of ?

Probably not technical. There is another element, obtaining a HDD encryption key from the TPM. The idea that the HDD is encrypted outside of my laptop and nothing can boot on my laptop that isn't my signed OS to read it.

Thinking about it I probably could do everything in the kernel directly - why not? Well, because it would be extra work to write all that, but probably not a technical limitation.

dataflow2• 2 years ago

I've thought about something like this before, but I have so many questions on just the basic premise...

First: Linux could already be booted directly from the UEFI manager. You don't need GRUB at all. So why a new scheme - why weren't they just doing that?

Second (and third, etc.): If I have multiple Linux installations along with a Windows installation, wouldn't this mean one of them now has to be the one acting as the boot loader? Could it load the other one regardless of what distro it is, without requiring e.g. an extra reboot? And wouldn't this mean they would no longer be on equal footing, since one of them would now become the "primary" one when booting? Would its kernel have to be on the UEFI partition...?

rcxdude10• 2 years ago

Booting linux directly just boots you into that install. It doesn't give you a boot menu or any of the other functionality GRUB provides. This project is basically proposing building that in a small initramfs userland instead (which has the advantage of requiring much less effort and code duplication). It's functionally very similar to GRUB, including with regard to your last point: generally speaking at the moment one OS needs to be managing the boot menu, and when they fight over it things go badly (see the status quo where Windows will occasionally just insert itself as the default after an update). UEFI could in principle have fixed this, but the inconsistent implementation between vendors makes it an unreliable option for OS developers.

(And in principle this system could load other linux distros assuming there was some co-ordination in how to do so. Windows is more difficult, as is interaction with secure boot)

dataflow2• 2 years ago

Booting linux directly just boots you into that install. It doesn't give you a boot menu or any of the other functionality GRUB provides. This project is basically proposing building that in a small initramfs userland instead

I indeed understood that part, but their motivation for this was security. If you want security, you should want to boot directly into the kernel. And if you're the occasional user who has multiple OSes installed in parallel... you can just add more kernels from your dual-boot installs directly to the UEFI screen; there's really no need to go through any form of intermediate stage, whether kernel-based or boot-loader-based.

What I'm trying to say is: as cool as this is from a technical standpoint, I just don't understand the root of the premise or motivation here whose optimal solution is this approach. Whom is RedHat trying to please with this? The small fraction of users who dual-boot Linux, or the rest of the users who just have a single install? And what problem are they actually trying to solve -- security, performance, or something else? Because the optimal solution to the first two doesn't feel like this one, unless they're targeting a niche use case I'm not seeing? e.g., do they have lots of enterprise users that boot off a network, but whom would rather have a local Linux install whose sole job is to boot that...?

jagrsw• 2 years ago

I get truly confused when using GRUB. Maybe it’s just me being unwilling to dive into all the details, but seriously, why are there like 30 packages starting with 'grub' under Debian? All I want is to boot my kernel under EFI, and the package choices are overwhelming.

  grub-common
  grub2
  grub2-common
  grub-efi-amd64
  grub-efi-amd64-bin
  grub-efi-amd64-signed
  grub-efi-amd64-signed-template
  grub-efi-amd64-unsigned
  grub-efi
  grub-pc
  grub-pc-bin

Do I need to mix grub2 and grub packages to get it to work? Currently I do, and a bit afraid to remove one or the other :)

Usually, I end up trying things randomly (leaving some funny mess in /boot/EFI b/c not sure if --efi-directory should contain /boot/EFI prefix, or just /boot or nothing), then running some semi-random grub-install command, and eventually, it starts to work. But this is far from intuitive.

lmm2• 2 years ago

Maybe it’s just me being unwilling to dive into all the details, but seriously, why are there like 30 packages starting with 'grub' under Debian? All I want is to boot my kernel under EFI, and the package choices are overwhelming.

Debian packaging policy is insane, that's nothing to do with grub. On a regular distribution there is one (1) grub package (e.g. I just checked Slackware and Gentoo).

kevinoid• 2 years ago

This approach sounds similar to Petitboot <http://www.kernel.org/pub/linux/kernel/people/geoff/petitboo...> which is a kexec-based bootloader that I used on the Playstation 3 many years ago. Apparently it now targets many other systems and there is a (dead?) fork for Coreboot <https://github.com/ArthurHeymans/petitboot_for_coreboot>.

hackernudes2• 2 years ago

The Q&A mentions this[1] and says Petitboot requires two kernels (one minimal one + one normal one). NMBL just uses one single kernel for both steps.

[1] around 23m20s https://youtu.be/ywrSDLp926M?t=1400

hackernudes2• 2 years ago

In the "what do we have so far?" slide they explain there are currently two variants of NMBL, one that does a switch_root (like a normal initramfs) and one that does kexec (to boot into a new kernel). It presents a menu for the user to select what to boot. It also will allow rolling back to the old version when boot fails.

I see some other comments in this thread about hypothetically supporting booting other UEFI targets and some ideas on how that would be implemented.

There is a question in the video about chainloading around 27 minutes -- https://youtu.be/ywrSDLp926M?t=1640 but the answer isn't clear to me - "setting FE variables". Is that frontend? firmware environment?

JoeAltmaier2• 2 years ago

Not sure why loaders are a separate beast any more.

In the bad old days, ROMs had very limited space. Lots of bootloader packages got invented, tiny things that knew just enough about ROM and the filesystem to get the 'real' code loaded, maybe un-zipped, maybe unencrypted. Later, some network-boot options which were handy.

Today? The boot flash is huge (compared to ROMs). You can put an entire OS in there! In fact, nowadays the bootloader is often a flash partition right next to other OS images.

I assert, there's nothing that a bootloader can do that an entire OS e.g. Linux image can't do. Just build a linux image, put a boot-script in there to allow network-boot or reboot-from-another-partition. And be done with it - no more u-boot, no more obscure bootloaders with limited drivers and options.

The day of the bootloader is over.

nickelpro• 2 years ago

The reason is very simple, you only get to call ExitBootServices() once (absent hacks that hook the function).

If you want to be able to do anything prior to calling ExitBootServices(), such as choose what EFI application you want to use and options you want to pass it, you need a service built to provide you that interface which itself does not call ExitBootServices().

The name of that service is the bootloader.

JoeAltmaier2• 2 years ago

...which should simply be another build of a real OS. Not some weird beast we inherited from the bad old days of tiny ROMs.

CodeWriter23• 2 years ago

So, move all of GRUB’s complexity into the kernel

(or tell users to abandon all their use cases that led to the aforementioned complexity)

ahmetozer• 2 years ago

I have been used similar approach at embedded system to copy data ram and kexec kernel there

raggi3• 2 years ago

An EFI stub that sets up multi-boot, kernel and initrd then jumps into it is pretty simple.

I don't know why people really need to keep putting huge intermediate loaders in every default boot path.

If you want to boot more than one OS, yes you need one of these, but if you don't then there's no need for yet another OS instance in the boot path. The mid-stage should be extremely small and simple.

There's been so much crying over the size of UEFI, well now there's an arbitrarily versioned and maintained entire Linux in there too? Mostly just to avoid some ugly UEFI APIs and a slightly different programming environment? Yuck.

raggi3• 2 years ago

To state this slightly differently:

GRUB has a terrible security story, a key point in the posted presentation. GRUB is huge and has design traps which contribute to regular developer mistakes.

Any huge solution here will suffer the same problem, the larger it is the more likely the problem is.

You don't really need much to do work here, a UEFI program can walk through the directories in the ESP and make choices, and perform assertions, so keep your A/B/R kernel and ramfs objects in there (as UKIs, as separate files, whatever). It can make a choice and boot the thing.

If you want user choice you could put menus into that program too, but you don't need them for most users, so leave them out, that's a ton of deps gone.

A basic program to do this isn't more than 1000 lines, it'll be low on maintenance and exceptionally low on critical flaws.

It's not hard writing even fairly complex things for EFI, here's Fuchsia's UEFI stage which is designed for development and has far more features (fastboot, mdns discovery, etc) than most of these things need. It's still tiny compared to the grub stuff: https://fuchsia.googlesource.com/fuchsia/+/refs/heads/main/s...

snvzz• 2 years ago

I'd say grub is crap, let's switch to das u-boot, which is not.

juped3• 2 years ago

If you want to boot more than one OS, yes you need one of these

Nope, you only need refind (a fancy menu, not a bootloader at all), and only then because of how impoverished the vendor's boot menu always is; if your configuration is simple enough you could just use that despite it sucking.

E39M5S624• 2 years ago

It's nice to see more people embracing the capabilities of UEFI and Linux. ZFSBootMenu has been shipping an EFI application (really, a UKI masquerading as one) for almost four years now - https://docs.zfsbootmenu.org/en/v2.3.x/ . The neat part is that the first stage kernel boots in roughly 1.5 to 2 seconds. It's not really appreciably slower than other boot methods while at the same time exposing a substantial amount of pre-boot functionality.

account4211• 2 years ago

The neat part is that the first stage kernel boots in roughly 1.5 to 2 seconds. It's not really appreciably slower than other boot methods while at the same time exposing a substantial amount of pre-boot functionality.

That sounds 1.5 to 2 seconds slower than just having efistub in your main kernel image, which honestly is a LOT. Of course not possible with problematic drivers like ZFS but then you don't have to use those.

E39M5S624• 2 years ago

Yes, and then your main kernel image is no longer on ZFS and you lose the ability to reliably roll back your root dataset. Everything is a trade off. I reboot my workstation once a week for a kernel upgrade, so an extra 2 seconds of boot time isn't even a consideration.

teo_zero2• 2 years ago

I'm a big fan of compiling my own kernel with all needed drivers compiled in, with the EFI stub compiled in, no initram, no grub, a fixed cmdline that works 99% of times.

This allows a boot to happen in less than 5 seconds.

The 1% of times I need something different, I use the boot selector provided by the firmware to boot to grub (that's installed anyway), where I have the usual plethora of choices.

Is there a key to be pressed at the right moment? There is. I even have to insert a password. So what? I can go through such ordeal once in a while for that 1% of "special" boots.

qhwudbebd3• 2 years ago

I completely agree, over time I've found myself moving to doing exactly this on every system I run. On UEFI systems, I can use the UEFI shell to add kernel command line options or launch a fallback kernel if I've screwed up badly enough to break boot. I don't need yet another layer of clunky menus and indirection.

joveian2• 2 years ago

This link that has been posted a couple of times is a much better source for those of us who aren't going to watch a video:

https://fizuxchyk.wordpress.com/2024/06/13/nmbl-we-dont-need...

msla• 2 years ago

I can't wait until the big distros decide multi-booting is a feature "nobody uses" that "never worked" and therefore isn't going to be supported because "everyone can use VMs" and containers and whatever other solutions that do not, in point of fact, solve the problem.

https://en.wikipedia.org/wiki/Multi-booting

account4211• 2 years ago

It does make sense for most distros to not care about that TBH. Advanced users can always put a boot menu in front of whatever their distros provide if the EFI-provided menu isn't sufficient.

nardi• 2 years ago

Meta: Can someone with Linux/bootloader knowledge tell me whether most of these comments are as clueless as they seem?

juped3• 2 years ago

Many seem a bit confused but I have only skimmed the comments.

I don't understand the point of the thing described in the OP (I have not watched the talk, just skimmed the notes), myself. Linux kernels can EFI load themselves; if you want more flexibility than a precompiled kernel command line, or to load from ext4/other non-FAT filesystems, refind exists, fits on the ESP (kernel + initramfs can get big; I keep mine on the ESP but wanting to keep it on a larger ext4 filesystem is very understandable) and is very high quality.

Bootloaders are obsolete in this sense; every OS provides an EFI stub loader, except Linux where kernels are their own EFI stub; nevertheless, distros continue to install GRUB alongside themselves on UEFI systems out of inertia. If Red Hat wants to supplant it... okay, but it can be supplanted today with very good components, even if they weren't invented there.

creshal4• 2 years ago

If I had a nickel for every time the RedHat ecosystem overengineered itself into a corner and decided the only possible solution was more overengineering, I could probably buy IBM.

pmorici• 2 years ago

Does anyone have any tips for debugging EFI_STUB kernels when they fail to boot? I've run into BIOS before that I can't get EFI_STUB to work on but grub works fine and I'm not sure why or even how to go about getting any debug info since the bios/firmware is a block box. Is the only option to get in touch for the motherboard vendor and how they care to look into it? It's rare but happens.

mmphosis2• 2 years ago

A removable physical key: a programmable ROM.

I have programmed the ROM to instantaneously copy my ROM to RAM and run. The entire system is running instantly as soon as I power on. There is absolutely nothing else.

Because everything else is a big mess:

Intel ME, BIOS, UEFI, kernels are signed by companies with Microsoft's blessing, EFI, FAT, TPM, anything with the word "Secure" in it, ...

katzenversteher• 2 years ago

Please elaborate. What kind of key are you using? What are you booting? On which architecture / machine?

mmphosis2• 2 years ago

What kind of key are you using?

I want this because right now I use camera cards to boot. The key needs to be wired directly to the processor and be the first and only entry point. Instantaneous boot is what I want, not resuming from hibernation but "instant on" of the full system.

What are you booting?

I am booting Linux, BSD, custom systems, lightweight bootstrap programs that do a specific task like diagnostics.

On which architecture / machine?

Agnostic / various. For instance, instantaneously booting / running only on GPU(s).

gorgoiler• 2 years ago

It’s a pity we aren’t really there yet with boot loading. In 2024 if I install an OS it places a boot loader in my EFI System Partition but in a way that still feels only partially complete.

What I want is for each OS to install its loader in a unique directory to that OS instance, not unique to the OS vendor. Multiple Debians etc will argue over who controls /debian. You also have to bless UEFI with magic NVRAM variables when it could just scan my EFI System Partitions for any file named “loader” and present that as a boot option.

Perhaps I should just chain from UEFI to something smarter that skips the UEFI-standard and does this smarter thing instead? Debianised GRUB tries to be smart at update-grub time in order to detect OSs but it would be neater if the loader did it.

Edit: In fact I see this is exactly the goal of rEFInd https://www.rodsbooks.com/refind/ …in particular it laments how “EFI implementations should provide boot managers [but] are often so poor as to be useless” so it tries to do a better job for you. I’ll give it a go.

juped3• 2 years ago

refind will scan all your partitions for EFI bootable things; if you have two ext4 partitions each with a Debian on them, and each has a Linux kernel in /boot, it'll locate them both and you can boot either. Which sounds like what you want.

pabs3• 2 years ago

Theres the removable media path:

https://wiki.debian.org/UEFI#Booting_from_removable_media https://wiki.debian.org/UEFI#Force_grub-efi_installation_to_...

iam-TJ• 2 years ago

A small side-note to solve your "unique [EFI-SP] directory to that OS instance":

In each GRUBified OS instance, in /etc/default/grub (or on Debian and derivatives, to avoid altering the distro-shipped config file, /etc/default/grub.d/local.cfg ), set:

GRUB_DISTRIBUTOR=

This is used by grub-install.

If calling grub-install directly one can also pass --bootloader=id=

The value is set via efibootmgr's --label

winkelmann• 2 years ago

FYI: In my experience, modern UEFI Firmware/BIOSes will scan every FAT32 partition found on attached storage devices for bootable EFI binaries, they don't even appear to care about the GUID/type marking, just that it is FAT32. I never let OSes share an ESP, each install gets its own.

egberts13• 2 years ago

I prefer my bootloader (be that it may, GRUB, lilo, or even BusyBox) because thosr image will go away once the kernel is started.

Nothing for hacker to see and analyze the bootloader, assuming you did not load a driver to the NVRAM/Flash/UEFI/EFI.

Nice security compartment alization.

Redhat is smothering this easential security abstraction of 1st stage loader: not a good security model.

TheDong2• 2 years ago

Can you explain more what security vector you're talking about here, because I just don't see it?

Like, as far as I can tell, grub or whatever is a bundle of filesystem and device drivers, with enough info to then execute a kernel.

Linux also is a bundle of filesystem and device drivers, but better tested ones I think.

To me, it seems like using the kernel's filesystem drivers, which you have to use already anyway once you've booted, means you have to trust fewer total implementations of these drivers, so it seems more secure.

What attack or threat vector are you trying to talk about here?

egberts13• 2 years ago

It is the same security abstraction where you don’t allow support for network socket in process ID 1.

(Looking at you, systemd.)

You don’t allow access to the bootloader from any kernel, thereby afford a relative security in starting 2nd stage (kernels). One abstraction is that TPM, et. al., can lockstep assurances on each stage. At a minimum, you have a bootloader, in case of SNAFU/FOOBAR.

Bricking (or worse, malicious kernel) seems more a possibility with upcoming Redhat design.

cool_beanz4• 2 years ago

There's kernel command line parameters that can clean it up without a bootloader.

userbinator• 2 years ago

Does anyone still remember when you could just dd the Linux kernel to a floppy and it would be its own bootloader?

https://yosemitefoothills.com/LinuxBoot/BD-1Disk.htm

Here's some more documentation on this: https://www.kernel.org/doc/Documentation/x86/boot.txt

What's old is new again... except 100x more complex and likely more than necessary.

lproven12• 2 years ago

That is exactly what I thought of when I read this post, yes.

Thoreandan• 2 years ago

Just checked and amusingly I'd forgotten that boot/root predated LILO, I must've first seen LILO when I installed Softlanding Linux. Since I didn't have any networking on my home machine, Linux was basically a "Look, run GCC on your home machine!" option for '91 that didn't involve going through DJGPP's DOS port.

retrochameleon• 2 years ago

I use zfsbootmenu. It allows me to boot multiple OSes from different data sets, make and rollback snapshots, and even directly boot from a snapshot. It also has a minimal shell for zfs tasks.

bfung• 2 years ago

Yo Dawg, I herd you like bootloaders, so I put a bootloader in your kernel so you can boot w/a kernel while you boot a kernel.

mixmastamyk4• 2 years ago

I recently moved to sdboot and prefer its simplicity compared to grub. However they still missed the mark a bit, its folder tree on the ESP is a mess.

I’ll look into this but prefer kernels managed automatically by apt/dnf etc.

creshal4• 2 years ago

sd-boot on Debian 12+ is mostly self-configuring, and the folder structure is just one folder? Not sure what's messy about that.

mixmastamyk4• 2 years ago

On fedora it is 10+. Do a tree command on the efi partition.

lproven12• 2 years ago

You are not clear; by "sdboot" do you mean systemd-boot?

The abbreviation is ambiguous. There are other bootloaders called "sdboot" such as this one:

https://sourceforge.net/projects/sdboot/

And this one:

https://www.reddit.com/r/WiiHacks/comments/glx4dt/sdboot_eve...

Please try to avoid ambiguous abbreviations. If you do mean systemd-boot you only saved 5 letters and could mean at least 3 different tools, or maybe more.

mixmastamyk4• 2 years ago

Yes, sorry when installing in fedora you have to pass the string sdboot to the kernel at boot. Still kinda experimental.

eqvinox3• 2 years ago

relevant comments from Hector Martin over on Mastodon at https://social.treehouse.systems/@marcan/112754303893998372

Reminder that not all platforms support or, indeed, can support kexec() sanely at all. Like ours. kexec() requires the ability to reset all peripheral state and that is impossible on Apple Silicon because firmware is loaded by earlier boot stages and cannot be re-loaded later to the reset state without a full system reboot.

TimGhost• 2 years ago

Sounds like Apple sorted itself out by themselves, while suffering from the limitation.

So the correct response to this concern is "Okay. And? Apple will just sort itself out for themselves". I mean, what else can anyone do? Nothing because "but Apple?"

eqvinox3• 2 years ago

This discussion is about how to boot Linux, not how Apple's OSes do things on their devices. Booting Linux on a Macbook is the affected scenario.

ale424• 2 years ago

See also this project: https://github.com/zhovner/OneFileLinux

Not a bootloader, but a single-file, very light Linux image that can be loaded directly as an .EFI file. Not useful as an actual OS for daily use, but can have specialized uses (I used it to network boot a whole room of PCs to a Linux showing a slideshow on the framebuffer).

ale424• 2 years ago

See also https://news.ycombinator.com/item?id=40914761, just posted on HN. Website of the project: https://hub.zhovner.com/geek/one-file-linux/

account4211• 2 years ago

I haven't used GRUB since my first EFI system. The EFI itself is already a bootloader after all, why would you need another one, especially one as bloated as the new GRUB.

itvision3• 2 years ago

To pass kernel parameters? How would you do that without a bootloader?

account4211• 2 years ago

EFI can pass kernel parameters just fine, both in the default boot entries or when running the kernel from the EFI shell.

itvision3• 2 years ago

Is the motherboard's NVRAM supposed to be written to so often?

I'm not sure about that.

eqvinox3• 2 years ago

It originally used to be actual RAM with a battery backup. These days it's generally NOR flash (because it's small enough for savings from using NAND to not apply, and the complexity of NAND instead raising the cost). NOR has quite high write cycle tolerance/limits.

akagusu• 2 years ago

https://docs.zfsbootmenu.org/en/v2.3.x/

nicman23• 2 years ago

you do not use grub for being fast. you use it for when things go wrong

conaclos• 2 years ago

I use EFISTUB [1] to directly load the Linux kernel. How is nmbl different?

[1] https://wiki.archlinux.org/title/EFISTUB

1oooqooq4• 2 years ago

I will translate the doublespeak from redhat, which is similar to how they started to push systemd (really).

[grub] features create complexity that is difficult to maintain, and that both duplicate and lag behind the Linux kernel while also creating numerous security holes.

No mention of the alternatives. No mention how useful are those features. Handwaiving "security" arguments.

Loaded by the EFI stub

All the talk about booting the kernel directly is moot, because by this they mean "we will use systemd-boot" ;)

IMHO, this is part of the RH wider push for PKCS11/TPM2/FIDO2 stuff. So it is not really fixing boot loader, as it is standardizing on their bootloader "as the correct one" but using the kernel reputation on the double speak.

Just like they pushed the equivalent of https://www.tenforums.com/attachments/tutorials/195499d15314... as the interface of init. (i'm not salty on systemd, in fact i already use bootd even. but if you cannot see how systemctl is the same UX as that, you are blind)

1oooqooq4• 2 years ago

I should say *the joint RH/Microsoft/et al wider push for PKCS11/TPM2/FIDO2 stuff

rini172• 2 years ago

EFI stub is an existing kernel feature, not related to systemd-boot. Of course, everything can be wired together with systemd.

1oooqooq4• 2 years ago

but it doesn't cover any of the unmentionable features that are so bad on grub. they will either be implemented in the kennel or the stub, because well, people will need dual boot, weird crypto, etc.

exactly like happened with systemd. all the complexity was ignored.. then bolted on. do you miss crontab -e?

abofh• 2 years ago

To be fair, it's similar because it's the problem people wanted solved - start this thing at boot, if it dies, restart it. I know rcS.d didn't handle the 'restart it', but even for the lowliest desktop user, if they've installed a daemon, and configured it to start, it more or less implies they'd like it to keep running.

Systemctl looks a lot like a modern init on another OS because a modern init on any OS looks a lot the same. Whether it should spawn 1800 subprojects is a different debate, but I for one am much happier maintaining trivial .ini like files than trying to teach the new engineer bash.

collinmanderson2• 2 years ago

systemd-boot comes up in the Q&A at 29:50. (The main problem nmbl is trying to solve is code-duplication with the kernel and therefore security issue duplication, and just like grub or any of the alternatives, systemd-boot duplicates code that's already in the kernel. The security holes will exist in any case, but the goal is to reduce security hole duplication by reusing as much of the kernel as possible, rather than creating something separate. They also plan on reuseing grub's menu code, so it will have the exact same menu as grub.)

The question is: that there are CVEs everywhere, we're not unique in this sense, and whether we would use systemd-boot.
So, systemd-boot, it also works only on UEFI, and I believe that the plans are to keep it that way.
Ultimately, the thing is that the kernel CVEs will get fixed no matter what, the question is: do we want to have more work fixing more CVEs. The kernel has a lot of developers, has very high visibility, and they're able to fix the CVEs in a reasonable time period. And, those aren't going to going to go away, the kernel CVEs aren't going to go away, whether we do this or not.
Systemd-boot, any boot loader, that aims to replicate the things that the kernel does is ultimately going to run into the same problems as grub. We're going to have the font CVEs, we're going to have filesystem and storage and memory allocation bugs. All of that stuff is going to exist in whatever boot loader.
Again, for an individual user, if you want to install systemd-boot, great, go ahead and use it. It's good, it works. But as a general option it's just going to have the same issues, unfortunately.

joveian2• 2 years ago

This seems like it could be a good use of rump kernels, although I don't think anyone has made a bootloader based on NetBSD rump yet. I've heard of efforts to rumpify Linux but I don't know if they are continuing. This seems like it could offer the benefits of each approach. The rump kernel paper has this brief paragraph on bootloaders:

The lowest possible target for the rump kernel hypercall layer is ﬁrmware and hardware. This adaption would allow the use of anykernel drivers both in bootloaders and lightweight appliances. A typical ﬁrmware does not provide a thread scheduler, and this lack would either mandate limited driver support, i.e. running only drivers which do not create or rely on kernel threads, or the addition of a simple thread scheduler in the rump kernel hypervisor. If there is no need to run multiple isolated rump kernels, virtual memory support is not necessary.

blucaz• 2 years ago

Systemd-boot, any boot loader, that aims to replicate the things that the kernel does is ultimately going to run into the same problems as grub. We're going to have the font CVEs, we're going to have filesystem and storage and memory allocation bugs. All of that stuff is going to exist in whatever boot loader. Again, for an individual user, if you want to install systemd-boot, great, go ahead and use it. It's good, it works. But as a general option it's just going to have the same issues, unfortunately.

This is completely wrong though - the main point of sd-boot is that it does _not_ implement any of that - no filesystems, no fonts, no themes, nothing at all, the firmware is used to do all the risky stuff via the UEFI protocols. So it is very much not reimplementing what grub or the kernel do, the exact opposite in fact, it's the number one design goal.

darby_nine• 2 years ago

Although GRUB is quite versatile and capable, its features create complexity that is difficult to maintain

The same is true of the kernel. Perhaps redhat should abandon linux and commit to grub, which has the potential to boot an even more interesting or useful kernel.

nottorp2• 2 years ago

If I look and think that this is another move by redhat to replace a simple independently developed solution with one that's complex enough to require a red hat issued certification, am I paranoid?

Actually wait. They at least haven't proposed to replace grub with systemd. Or is that buried in one corner of the presentation?

mpldr• 2 years ago

UKI isn't by redhat but by the Kernel devs, iirc. No redhead certs required. If you want to run with secureboot, you can use your own certs, but you can also just skip SB.

nottorp2• 2 years ago

Not certificates, certification ? As in Red Hat Valued Engineer or whatever they sell.

qhwudbebd3• 2 years ago

A slight tangent, but still kind of relevant: given that we're lumbered with UEFI on x86-64, are there any active projects working on a better UEFI shell?

Every time I interact with it, I am struck by how awful it is, but the shell is just an EFI application so presumably one could replace it with something better written. Searching turns up EFI menus aplenty, but no one has (yet) taken a shot at a simpler, cleaner EFI shell from what I can see?

WesolyKubeczek• 2 years ago

This sounds awfully like macOS on Apple Silicon, where the "boot menu" is in fact more or less full-fat macOS with special fullscreen GUI.

wvh• 2 years ago

I've been using `systemd-boot` for many years, which comes with the system. It's a bit simpler than Grub and LILO (team 90s, represent!). Most BIOSes have variable support for booting random images, but last time I got a new system, it was confusing to use and a bit of hit-and-miss.

techwiz137• 2 years ago

How about people moving away from 16-bit real mode(obviously a change is needed in the CPUs), removing that A20 line forgotten from history patch and actually booting like we are supposed to?

wkat4242• 2 years ago

I use whatever i want :P that's the nice thing about FOSS. I'll move on to the new cool hipster thing when I feel like it and if I see value in it..

Though generally I prefer the approach of "extend what we have with new features" over "rip out all out and start from scratch" so I spend my time mostly with the BSDs which don't jump full steam ahead into the whatever's the new thing.

Even though something like systemd is undoubtedly better in many things, I also have to wrap my head around it, see how to get at the logs, build those unit files etc. On the BSDs I don't have to bother with that and just keep working as I was and which was not broken for me.

The point is, something new doesn't only have to offer a tangible benefit for me to be worth it. It has to be such a big benefit for me that it offsets the hassle of getting my head around all the new stuff and most of the new Linux inventions fail at this.

matheusmoreira• 2 years ago

This is nice. I want to see Linux replace all kinds of stuff. Especially things like bootloaders, UEFI firmware and even on-device firmware.

ForOldHack• 2 years ago

Unix and Xenix did this. Single user mode. This is just a plea to have GNU/GRUB integrated into the kernel. I think it's a very good idea. Not original, but a seriously good idea. Add some more help and documentation. Pre-sets for most of the common scenaros. Multi-mode kernals? Kernals as a service?

And make no mistake, this is a compelling article.

StillBored2• 2 years ago

No, please don't.

Most firmware systems don't enable interrupts, support paging, SMP, or many other things, for a long list of reasons, while at the same time, in order to enable a full Linux environment, ExitBootServices must be called, which is going to make a mess anytime the booting kernel isn't the right one. Kexec breaks a fair amount of the time if the target kernel isn't exactly what was already booted (ex, see kdump failures). Nevermind if the target OS isn't linux.

And for what? So /boot can stick around? A legacy partition left over from the days of BIOS/MBR like systems that have to have a small partition at the beginning of the disk, formatted with something that supports linux file permissions?

No, the right solution is to just place the kernel(s), and a small signed initrd (s) in the ESP, and nothing else besides a boot selector, like say systemd-boot to allow the user to select the correct kernel/OS, and optionally edit debug/etc options. Then, when the correct kernel is booted, it can bring up the network, filesystem, and whatever is needed.

That solves an endless list of Linux and firmware interaction problems that Grub currently solves, without all the file system, network code, etc., that one finds in Grub, which mainly duplicates the functionality already provided by UEFI.

The problem with this solution is that it doesn't work on systems that aren't UEFI, to which I might suggest that those systems (cough, legacy IBM junk, or hyperscalers still using BIOS boot after it has been deprecated everywhere else) have either uboot-uefi or edk2 ported so they can conform to modern boot standards.

No more boot loader: Please use the kernel instead

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