No more boot loader: Please use the kernel instead
pretalx.com
pretalx.com
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.
> - 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...
Am I correct in understanding that the offered solution here is to first boot into System A, find some well-hidden EFI configuration utility (which varies from OS to OS, if it even exists), and then tell EFI to boot into System B on the next reboot?
If so, that's a pretty terrible experience.
Basically, System A's kernel boots. But, instead of immediately loading the System A userland, it loads a boot menu of systems that it reads from UEFI NVRAM and presents it to the user. So you select System B from the list, the menu sets BootNext in NVRAM and issues a reboot.
In practice, the main UX difference is that it takes a bit longer and you'll see the UEFI vendor splash screen again after selecting the boot option.
I'm not a user of Windows anymore but I seem to recall Windows doing something quite similar, where it had a boot menu that felt suspiciously like it was inside of Windows, and to actually change the boot target, it had to reboot.
I mean, it kind of is loading the System A userland. At least the initramfs of it. AFAICT in the proposal the bootloader would now be a regular userland program living in the initramfs.
I get the impression that the eventual goal would be to make this bootloader program into the "init(8) but for the initramfs phase of boot" — i.e. rather than there being a tool like update-grub that calls mkinitramfs, feeding it a shell-script GRUB generated (which then becomes the /init of the initramfs); instead, there'd be a tooling package you'd install that's related to the kernel itself, where you call e.g. kernel-update(8) and that would call mkinitramfs — and the /init shoved inside it would be this bootloader. This bootloader would then be running for the whole initramfs phase of boot, "owning" the whole bootstrap process.
What the architecture is at that point, I'm less clear on. I think either way, this initramfs userland, through this bootloader program, will now handle both the cases of "acting like a bootloader" and "acting like the rest of initramfs-based boot up to pivot-root." That could mean one monolithic binary, or an init daemon and a hierarchy of services (systemd: now in your bootloader), or just a pile of shell scripts like GRUB gives you, just now written by Redhat.
Why? What advantage is there for Windows to do this?
I guess it allows the bootloader to be much simpler, at least in theory.
Personally I still use GRUB for all of the reasons you stated above. But rEFInd + kernel gets you pretty close.
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)
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.
The fast boot involves skipping a bunch of slower pathways using saved knowledge of minimal set of devices to bring up to boot the OS in happy path, and only reset to "slow path" if it fails.
In fast boot, you're often unable to hit the button to enter the menu and at most get to it through windows "reboot to firmware" option.
If I could do the same with something that is as small in terms of footprint, and is as flexible as GRUB is (we also PXE-boot into GRUB loaded from the network, both in BIOS and UEFI mode), then I'm interested.
I think network booting with EFI would also suffer from a similar problem.
I would assume that in their proposed solution, the kernel would have logic to check for a CMDLINE flag (or rather, lack of any CMDLINE flags!) to indicate that it's operating in bootloader mode; and if decides that it is, then it never calls ExitBootServices. All the EFI stuff stays mapped for the whole lifetime of the kernel.
(Also, given that they call this a "unified kernel image", I presume that in the case where the kernel decides to boot the same kernel image that's already loaded in memory as the bootloader, then nothing like a kexec needs to occur — rather, that's the point at which the kernel calls ExitBootServices (basically to say "I'm done with caring about being able to potentially boot into something else now"), and transitions from "phase 1 initramfs for running bootload-time logic" into "phase 2 initramfs to bootstrap a multi-user userland.")
That's unlikely, I think that would mean you cannot use native drivers, at which point you're just writing another bootloader. I suspect they only planning to kexec into target kernel, not chainloading other EFI bootloaders.
> I think that would mean you cannot use native drivers
Yes, that's right.
> at which point you're just writing another bootloader
But that's not necessarily true.
Even if you could only use EFI boot+runtime services until you call ExitBootServices, in theory, an OS kernel could have a HAL for which many different pieces of hardware have an "EFI boot services driver" as well as a native driver; and where the active driver for a given piece of discovered hardware could be hotswapped "under" the HAL abstraction, atomically, without live HAL-intermediated kernel handles going bad — as long as the kernel includes a driver-to-driver state-translation function for the two implementations.
So you could "bring up" a kernel and userland while riding on EFI boot services; and then the kernel would snap its fingers at some critical point, and it'd suddenly all be native drivers.
Of course, Linux is not architected in a way that even comes close to allowing something like this. (Windows might be, maybe?)
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I think a more interesting idea, though, would come from slightly extending the UEFI spec. Imagine two calls: PauseBootServices and ResumeBootServices.
PauseBootServices would stop all management of devices by the EFI (so, as with ExitBootServices, you'd have to be ready to take over such management) — but crucially, it would leave all the stuff that EFI had discovered+computed+mapped into memory during early boot, mapped into memory (and these pages would be read-only and would be locked at ring-negative-3 or something, so the kernel wouldn't have permission to unmap them.)
If this existed, then at any time (even in the middle of running a multi-user OS!), the running kernel that had previously called PauseBootServices, could call ResumeBootServices — basically "relinquishing back" control over the hardware to EFI.
EFI would then go about reinitializing all hardware other than the CPU and memory, taking over the CPU for a while the same way peripheral bring-up logic does at early boot. But when it's done with getting all the peripherals into known-good states, it would then return control to the caller[1] of ResumeBootServices, with the kernel now having transitioned into being an EFI app again.
[1] ...through a vector of the caller's choice. To get those drivers back into being EFI boot services drivers before the kernel tries using them again, naturally.
It's a dumb idea, mostly useless, thoroughly impractical to implement given how ossified EFI already is — but it'd "work" ;)
AFAIK, the UEFI spec imposes no requirement that (non-hotplug) devices be re-initializable after you've already initialized them once. Devices are free to take the "ExitBootServices has been called" signal from EFI and use it to latch a mask over their ACPI initialization endpoints, and then depend on the device's physical reset line going low to unmask these (as the device would start off in this unmasked state on first power-on.)
Devices are also free to have an "EFI-app support mode" they enter on power-on, and which they can't enter again once they are told to leave that mode (except by being physically reset.) For example, a USB controller's PS2 legacy keyboard emulation, or a modern GPU's VGA emulation, could both be one-way transitions like this, as only EFI apps (like BIOS setup programs) use these modes any more.
Of course, presuming we're talking about a device that exists on a bus that was designed to support hotplug, the ability to "logically" power the device off and on — essentially, a software-controlled reset line — is part of the abstraction, something the OS kernel necessarily has access to. So devices on such busses can be put back in whatever their power-on state is quite easily.
But for non-hotplug busses (e.g. the bus between the CPU to DRAM), bringing the bus's reset line low is something that the board itself can do; and something that the CPU can do in "System Management Mode", using special board-specific knowledge burned into the board's EFI firmware (which is how EFI bring-up and EFI ResetSystem manage to do it); but which the OS kernel has no access to.
So while a Linux kernel could in theory call ExitBootServices and then virtualize the API of EFI boot services, the kernel wouldn't be guaranteed to be able to actually do what EFI boot services does, in terms of getting the hardware back into its on-boot EFI-support state.
The kernel could emulate these states, by having its native drivers for these devices configure the hardware into states approximating their on-boot EFI-support states; but it would just be an emulation at best. And some devices wouldn't have any kind of runtime state approximating their on-boot state (e.g. the CPU in protected mode doesn't have any state it can enter that approximates real mode.)
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
This sentence does not say "the bootloader is itself another, separate, Linux kernel", so I'm not seeing him saying what you're saying he seems to be saying.
This doesn't make sense. There's nothing in the post you responded to which could realistically be interpreted as making that point. And there haven't been any edits, which might have explained your confusion.
possibly you don't know this, but in order to run a kernel with a modified command line, the bootloader-kernel would need to run a second kernel, for example using kexec; linux doesn't have a useful way to modify the command line of the running kernel. that's why i interpreted the comment as saying that they are proposing using two separate kernels. in https://news.ycombinator.com/item?id=40910796 comex clarifies that they are in fact proposing using two separate kernels; the reason i was confused is that that's not the only configuration they're proposing
You can use the UEFI shell for this. It's kind of a replacement for the old MS-DOG command line.
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.
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.
Isn’t this how Apple’s Bootcamp works (at least on Intel based Macs)?
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).
If a motherboard doesn't have enough UEFI commands in its built-in Shell (or has no built-in Shell at all), you'll want to include your own Shell.efi file right there along with any startup.nsh you might decide to deploy.
This can also be good for USB booting where the removable USB device is in regular MBR layout rather than GPT-style-partitioning.
Whether or not the whole USB drive is FAT32 or not, as long as there is a proper EFI folder in a UEFI-recognizable filesystem, you can boot to any other OS on any other filesystem, depending only on the contents of the EFI folder. Unless there is a startup.nsh for the UEFI to follow instead, then you might not even need an EFI folder. As intended. Boot floppies still work as designed too. Startup.nsh is more commonly expected to contain reference to an EFI folder that is present on some recognizable filesystem, rather than work as a lone soldier though. GPT-layout partitions are not supposed to be necessary either, it's only needed when you want more partitions than legacy BIOS will handle, or partitions that are too huge for MBR representation.
Now any alternative to GRUB would by necessity have to perform more pleasingly on legacy-compatible systems where UEFI is not enabled also, or it will remain a less-effective alternative.
Once a geek is smart enough to handle both BIOS & UEFI, the more I would be able to trust their UEFI solution.
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.
GRUB_DEFAULT=saved
GRUB_SAVEDEFAULT=trueAnd is also themed like XBill.
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.
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.
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.
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.
Having to actually restart a PC is a pain in the ass which is why I don't dual boot.
is a pain in the ass? All the virtualization solutions are moot for gaming due to anticheat (plus 3d graphics virtualization not really working for windows)
For all laptops apart from Dell, Grub is the bootloader that EFI could never be.
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.
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)
Per, Korhojoa, and my personal experience plenty of desktop CPUs simply don't have integrated GPUs. Consumer mainboards simply don't come with them at all. Consider my previous workstation CPU, top of the line a few years ago and no iGPU: https://www.amd.com/en/products/processors/desktops/ryzen/50...
Integrated GPUs is a feature of server mainboards so that there is something to display with for troubleshooting, but not on any retail mainboards I am aware of. It is a feature of some consumer grade GPUs designed for either budget or low-power gaming. It simply doesn't exist on all CPUs, consider the AMD 5600, 5600x and 5600g, last gen mid-range CPUs adequate for gaming and the x had a little more clock speed, and the g had an iGPU.
So you are contradicting yourself.
- buying a ready made computer from a brand --> always come with an integrated GPU. Some will be even such a small form factor you have to use an external thunderbolt connected GPU if you want to use one.
- you build your computer yourself from parts --> you decide your motherboard and CPU, if VM passthrough is something you want to do, you just buy the parts that fits your use case
- you buy a configurable prebuilt computer from an online or local vendor --> you just have to choose the right option on the configuration tool so that you get a motherboard/cpu that offers integrated GPU.
- you buy second hand and you don't have an igpu: you buy the cheapest gpu available, usually around 10 to 25$ and you have your second GPU that the host can use.
Even when you are using laptop, having 2 GPUs is really not complicated in 2024, especially with thunderbolt external GPU cases/adapters.
Bottom line: you only have one GPU if you actively choose not to have 2.
It sounds like a useful toy for those whom already enjoy playing with their computer as much as playing with the game.
That said wouldn't limiting the host to integrated graphics (or whatever you get for $25) be a substantial limitation compared to using wine/proton or dual booting?
Most people don't play game.
Most people that play game that isn't solitary or a web game just buy a playstation, xbox or Switch.
Only a relatively small fraction of people playing AAA games use computer for that. The most hardcore one and the most willing to spend money on a game Rig. And I am pretty sure most of them aren't the least interested in dual boot because they would have a desktop gaming rig and a laptop for everything else anyway. Only a tiny fraction of gamers is probably interested in dual booting. You are part of that tiny group. Fine. The nmbl tool presented in this conference do not prevent dual booting anyway so I am not even sure why people act like they should be offended because grub might be replaced someday by something else with more capabilities.
You are correct on the complexity cost and how most people, even those with nice gaming computers, just don't want to deal with more complexity than needed. Even mandating a store app that works causes a significant hit to conversion rates. EA couldn't give away Dead Space a previously successful AAA title when bundled with their store.
Whales.
https://linux-hardware.org/?view=os_dual_boot_win
It doesn't make sense to ex post facto try to justify what people SHOULD do when we can look at what in fact they actually do.
The idea that the only people that play PC games are ONLY play AAA games on their souped up rigs is also a counterfactual. People play games everything from 8 year old laptops to $5000 custom built rigs with RGB everything. You are oversimplifying the universe consists of many and varied irrational individuals not spherical cows.
Dual booting is simple and suitable for nearly 100% of machines running Linux.
Wine/Proton is suitable for nearly 100% of machines running Linux. Steam has reduces this complexity to a few clicks for the majority of titles.
GPU passthrough is unsuitable for 70-80% of configurations and by dint of complexity undesirable for nearly everyone which is why virtually nobody does this.
Why would one dual boot if games work so well?
Yes. I work on Linux and play most games on Windows. Playing games on a VM is... pretty terrible.
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.
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.
While if don't dual boot you can switch completely to another OS and only use VM or remote desktop for the handful of use cases when you aren't ready yet (and then end ip abandoning them completely as well).
The experience of using a VM is not good, that's exactly why people are doing dual boot. They know what they are doing.
Keep in mind that booting takes a tiny fraction of the time today that it did in the 90s.
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.
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.
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.
UEFI is just a standard interface, not an implementation of a bootloader. This enables multiple UEFI compliant implementations as well as an easy way for OS to support all UEFI based bootloaders without needing to coordinate with the owner of the bootloader. While I'm sure most would agree the UEFI interface may not be ideal, it has a lot of industry momentum, and is therefore probably the best option to get behind. There are a lot of players in this space (mostly hardware vendors) and coordinating anything is very difficult and takes a very long time.
UEFI is more restrictive -- and tightly controlled by large industry vendors, not the community -- than either of them.
So, no, I totally disagree on all points.
Sure, in the happy path, you can depend on OpenFirmware giving you parameters like locations and addresses and "this device is compatible with X so you can use its driver", but it still requires that you have the specific driver the device is compatible with, and a new hardware release was often incompatible with older versions of OSes because, unlike ACPI, you can't encode information like "Hey, I'm compatible with interface X version Y" => "here's limited functionality because your driver is not updated for interface X version Y+1 but the computer will work".
Instead you had special "hardware support releases" to get the OS to boot at all.
CoreBoot and uboot by itself provide even less support. They might have open source, but they provide effectively closed platform to the end user. UEFI is in practice less restrictive because I only have to program to the interface, and in absence of gross bugs, I can expect things to work - whether it's a boot-time driver to support my super-duper-special storage add-in card, or a custom OS that I want to be available for normal people to try out by running on their random home PC. Hell, if Linux kernel people didn't tell they would no longer accept "platform definition" patches, you probably still wouldn't have FDT used on ARM with uboot.
However, ISTM that relying on a magic partition on a fixed disk is a poor design, and while other types of firmware are not radically simpler, there are or were alternatives, and some of them are noticeably more FOSS. UEFI is EFI for x86-64, broadly, and EFI was proprietary. That is not a good thing, in my book. Something more cross-platform and less vendor-dependent would have been preferable, even if of comparable complexity.
UEFI mandates certain, user and developer and admin UX nice, minimums regarding boot process. You can fully expand on supported filesystems, or even non-FS sources to boot from. Even from paper tape if you want to. You're not bound to magic partition on a fixed disk[1] anymore than you're with OpenFirmware (and decidedly less than IBM PC BIOS compatibles).
None of the comparable alternatives were really FLOSS (by the time OFW went open source, EFI was shipping on x86 and amd64[2]), coreboot/uboot/redboot/etc were too limited, by themselves being e-waste framework unless paired with upper layer to provide open platform for users and developers.
EFI was available, back in 1.1 timeline, as open source code for x86 and IA-64 (the IA-64 specific bits were called "SAL" IIRC), then some bright mind at Intel decided to close it down. Fortunately they open sourced it back as TianoCore and we now have FLOSS solution (it's as proprietary as OFW at this point in time, and it's more of an open platform than uboot/coreboot/etc).
The available "less proprietary" options all created closed platforms, where you need excessive porting to boot anything the vendor didn't ship for you. It's trivial to make firmware so flossy it will make RMS shed tears of nostalgia for KA-10, but it's not going to be useful for majority if they ever want to run something not provided by vendor. Minicomputer/workstation complex firmware monitors etc. happened because diagnostics were often needed, and some required at least some compatibility with third party hardware, but them - including origins of OpenFirmware - implicitly accepted a closed platform where vendor would need to ship a special "hardware enabling" OS update or ship entire OS version to match new platform.
UEFI might have proprietary roots, but it (and ACPI) is designed specifically to provide for the case of freedom of end owner to run whatever crap they want, including older version of OS they already got used to.
[1] Unless the hardware is too cheap, like Qualcomm ARM systems with UEFI where various critical services are patched in windows drivers to be handled through magic files on ESP, or in permissible CHRP OpenFirmware variants where magic partition on fixed disk is explicitly mentioned as an option.
[2] EFI based firmwares started shipping by 2005~2008 timeframe on x86 and amd64, mainly due to DXE providing way easier method to integrate 3rd party code. It was also from start designed to handle multiple platforms, partially thanks to having IA-32 and IA-64 code simultaneously as early as EFI 1.0, which made it easier option to handle future 64bit platforms.
https://web.archive.org/web/20100105051711/http://www.intel....
It was originally called Intel Boot Initiative, IBI.
https://www.afterdawn.com/glossary/term.cfm/intel_boot_initi...
You're right, work started in the late 1990s, but AFAIK nothing shipped until the 21st century: 2001.
For reference, it was possible to run it on x86 (and even the ICC with EBC was provided!) ~2001, including DUET which I ran from a floppy. There was close to same level of source access as today with TianoCore, though probably with different license.
Then someone at intel got a bright idea to close access to source and until the direction got reversed (which got us TianoCore) it was fully proprietary.
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.
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).
I don’t see the point of doing so however.
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.
...But to load it at boot time it absolutely must be done through an initramfs. Is that right?
Yes, because it cannot be part of the kernel image, or it would be illegal (a violation of the GPL license) to distribute that kernel. Therefore, it must be a module, and that module has to live somewhere and be loaded by something. If root is on ZFS, this must therefore live in an initramfs and be loaded by it so that the initramfs can mount the real root filesystem on the kernel's behalf.
That would probably make updates a lot less slower than having zfs shipped in an initramfs though.
The "problem" with the GPL here arises not when you, the end user, take a piece of GPL-licensed software and combine it with other software, as is your GPL-protected right, but when you try to redistribute the result. You see, every end user has the same right to obtain all of the source code for GPL-licensed software that they receive, and for all of that source code to be licensed in a way compatible with the GPL. Once the kernel and non-GPL-licensed modules have been combined into a single piece of software, you are free to use it locally as you wish, but you can't share it, because you would be unable to meet the obligations you owe to the person you give it to.
Bear in mind that the modules are meant to be combined with the kernel, and the method by which that happens isn't specified by the module authors. So, a tool which makes all of this easier for you to do isn't circumventing any restriction meant to stop you from doing this, because no such restriction exists.
Is this the case though? I thought there was an argument that in order to create that tool - you would need enough knowledge that it would require you to basically create a derivative work.
No, not AFAICS; it is incorrect.
On UEFI the system boots from a FAT32 partition. Put the kernel directly on that FAT32 partition, and any necessary modules such as ZFS, and the kernel can load the ZFS module from FAT32 and then mount root directly without any need for an initramfs.
This is how systemd-boot works.
I am not advocating systemd-boot -- I found it a pain to work with -- but the point is that it's perfectly possible and doable. The initramfs is a bodge and it's time we did away with it. It should only be needed for installation and rescue media.
- linux tells the bootloader what folder the modules live
- bootloader just puts them all in memory
- linux just picks what it needs.
That's all the initramfs is anyways. The point is there's no reason to prebuild an image from inside Linux, you can just have grub assemble a simple fs on the fly.
But initramfs isn't so bad, and it allows things like ZFS root to have a modicum of smoothness and integration.
Though I only do it for my ARM based devices currently.
And if you're not throwing away build artifacts after each build, then getting stable updates is just a `git pull` and incremental make, which is usually very quick.
That is a lot faster than recovering from a backup.
When I was young and spry, I used to compile them with every new minor revision. Now, it is just maybe a couple times per year. I think that cooling it on how often I do it has helped it not become annoying.
Me too. I go back to within about 3 years of that.
But I expect my distro to handle this for me now.
If the distro compiled and updated the kernel for my hardware then there's be no need for an initramfs.
While initramfs was a simplistic kludge, the UKI idea does not fix it, it wraps a kludge inside a fugly ball of lack of understanding.
In many cases, you don't need initramfs. I rarely use one in embedded systems.
[1] https://optee.readthedocs.io/en/latest/general/about.html
You're reliant on the capabilities of the chip that you're working with, and a flaw in that can unravel everything that you've done. In one case, I had to disable the on-chip boot agent once things were provisioned because of flaws in their implementation.
In short, a signed applet could be sent to the chip to do things like read/write NAND or NOR, set fuse bits, etc. When an unsigned applet was sent, it was rejected as expected but they neglected to clear the memory contents in this case. So you could send a malicious applet, let it be rejected, and then just tell it to execute. It's kind of a fascinating writeup if you want to know more [1].
1. https://labs.withsecure.com/advisories/microchip-atsama5-soc...
the other direction is to put everything in systemd. :)
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.
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.
I did mention that the root filesystem had to be both not encrypted and not require any userland setup.
> 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
That wouldn't help, as the password is not usually used directly as a volume encryption key. In LUKS2 for example, a memory-hard KDF (Argon2) can be used to transform the password or PIN into a key-slot encryption key which is then used to decrypt that slot to obtain the volume encryption key (which is usually completely random and not at all related to or derived from any kind of password) in order to set up the dm-crypt mapping.
> just to avoid having an initrd.
No distribution has used an initrd in the last several years; initramfs reigns supreme now. They are not the same thing; an initrd is an image of a real filesystem (e.g. squashfs or ext2) that is read-only mounted onto / by the kernel during its startup, while an initramfs is (an optionally-compressed) cpio archive that is extracted to a read-write tmpfs (or ramfs if tmpfs is not available) mounted on / by the kernel during its startup and then the memory occupied by that cpio archive is freed because it is no longer necessary. An initramfs can also be built into the kernel image; an initrd cannot, and must be provided by a bootloader.
There have been several attempts to add features to the grub zfs code over the years, but there are several maintainers of grub who happen to be employees of Oracle, and typically the attempts go nowhere.
I personally can't recommend using grub anymore. The whole "just make 2 pools" solution is unacceptable, and until Oracle stops gatekeeping, their code becomes more obsolete in my eyes.
And if this bit is closed source, and something doesn't work, you don't have a recourse.
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.
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.
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.
Envious of trustees having netbooks.
Unfortunately nothing is "in itself" in the real world. All these so called security features end up locking down users more and more in their own devices.
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.
The code is here although it hasn't been touched it years: https://gitlab.com/samsartor/alamode-boot
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.
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.
If you bcdedit to be "Legacy" bootmenupolicy, you can select any OS from its simple non-touch text-based NT6 multiboot menu and it will boot right away without need for repost.
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...?
(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)
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...?
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.
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.
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.
> 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.
Or, at least: I certainly didn't have to do anything to the kernel for it to work. I'm just running whatever Void Linux is rolling with right now.
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.
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...
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...
Related:
https://en.wikipedia.org/wiki/Open-source_hardware
https://en.wikipedia.org/wiki/Right_to_repair
In terms of how modifiable UEFI is - this is what Boot Guard (Intel) and Platform Secure Boot (AMD) are intended to deal with. They both support verifying that the firmware is correctly signed with a vendor-owned key, which means it's not possible for an attacker to simply replace that code (at the obvious cost of also restricting the user from being able to replace it - I don't think this is a good tradeoff for most users, but it's easy to understand why the feature exists).
If you want to be able to fully verify the trustworthiness of a system by having full source access then you're going to either be constrained to much older x86 (cases where Coreboot can do full hardware init without relying on a blob from the CPU vendor, ie anything supported by Libreboot) or a more expensive but open platform (eg, the Talos boards from Raptor). If you do that then you can build this entire chain of trust using keys that you control, and transitively anyone who trusts you can also trust that system.
But there's no benefit in replacing all of the underlying infrastructure with code you trust if it's then used to boot something that can relatively easily be tricked into executing attacker-controlled code, which is why projects like this are attempting to replace components that have a large attack surface and a relatively poor security track record.
Anyone interested in the subject could Google (or search on their favorite search engine) "UEFI Vulnerabilities" -- for no shortage of issues/problems/security vulnerabilities.
Am I saying that an old BIOS is perfectly secure?
No!
But older BIOSes are an order of magnitude simpler, better understood, and more documented -- than UEFI is at this point.
If UEFI morphs to something else more complex in the future, which it probably will, given the track record of hardware boot/initialization code specifically, and software generally, then my advice at that point in time (10+ years in the future) will be "go back to UEFI, it's simpler, more documented and better understood than what we have now".
But not until that day, and then not unless every computer on the planet is, or has become absolutely incapable of initializing/booting from the older code.
As a generalized pattern/understanding in Software Engineering, older code / older software / older codebases (of whatever form, firmware, etc. -- in this case BIOS hardware init/boot handoff code) -- are generally smaller, simpler (less bloat for approximately the same functionality), vanilla, spartan, better understood, and have had many of their security issues found, fixed, and solved than their present-day over complex and bloated counterparts... (and, did I mention better documented?)
...but if so, is that asserted "security boundary" really an actual security boundary(?)
If the security boundary or "security boundary" -- is opaque in how it functions; if it is a "black box": (https://en.wikipedia.org/wiki/Black_box); if no one (other than potentially a few people who work for the manufacturer, or exist at the company subcontracting to build their Smart Key component (if the Smart Key is subcontracted/outsourced)) understands exactly how it works, then is it really "secure"?
(If so, then that sounds eerily similar to the "obscurity is good" (aka "transparency bad") side of the "Security Through Obscurity" debate that the Internet had, like 5, 10, 20+ years ago: https://en.wikipedia.org/wiki/Security_through_obscurity#Cri...)
Why not read the following:
"Gone in 20 seconds: how ‘smart keys’ have fuelled a new wave of car crime":
https://www.theguardian.com/money/2024/feb/24/smart-keys-car...
And you tell me?
My conclusion:
Perhaps less "security" (less of an asserted "security boundary") -- is actually more actual security -- at least in some cases -- at least in the case of the Ford Model-T...
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.
https://wiki.debian.org/UEFI#Booting_from_removable_media https://wiki.debian.org/UEFI#Force_grub-efi_installation_to_...
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
> [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)
exactly like happened with systemd. all the complexity was ignored.. then bolted on. do you miss crontab -e?
my point is that the alternative to "crontab -e" is writting two files with 10~20 lines in difficult to remember paths. it's impossible to do without a webbrowser nearby.
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.
> 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.
> 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.
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.
I suppose then the hope is that nmbl would basically be a general-purpose fully-featured replacement for grub, which seems to be going in the direction of being a full kernel anyway:
> one with quite some bells and whistles, with networking, complex storage, cryptography, http client, ca store and stuff (I mean, that's how I understand it, i.e. it should be able to load kernels from sources that require all that). It hence will need require regular updating (as much as the 2nd stage kernel most likely, if not more often, since it probably needs ca store built in), and quite possibly will break every now and then nonetheless, because it's basically a full OS you are boot as first stage.
- https://lwn.net/Articles/981149/
It sounds like if you don't need grub's complex features, then systemd-boot is probably the safest way to go, but if you do need grub's complex features, then nbml aims to be the safest and most reliable way to get those features.
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.
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.
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...
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.
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.
But then I think UEFI is also stupidly complicated, and ought to be whacked down to its core functions. Dinosaur, am I.
I've been meaning to get it ready to release publicly. It's mostly there, just a bit manual to install.
https://fizuxchyk.wordpress.com/2024/06/13/nmbl-we-dont-need...
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.
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.
[1] around 23m20s https://youtu.be/ywrSDLp926M?t=1400
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.
(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)
As a device owner you have the option to recompile your kernel to disable any of the root/kernel barriers - when we designed Shim we did so in a way that ensures that you're always able to disable secure boot. Or you can simply disable secure boot entirely (another feature offered by Shim) at which point the kernel will disable most of those features. But by default the kernel will still, for example, refuse to allow even root to mmap() address regions belonging to hardware - some of those restrictions are down to "This has a high risk of causing accidental data corruption" rather than anything nefarious.
And make no mistake, this is a compelling article.
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.
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, ...
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).
Actually wait. They at least haven't proposed to replace grub with systemd. Or is that buried in one corner of the presentation?
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?
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.
- 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...)
> 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.
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?"
fs0:linux.efi root=/dev/nvme0n1p1 initrd=ramfs.img loglevel=2
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?
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.
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.
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
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.
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).
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.
Why enumerate usb devices on boot, when you have zero devices that need usb? Raid speed testing... and the list goes on.
Are you sure? On servers there are generally a couple of USB based devices which handle BMC, hardware debug logging, etc. Just because you don't have physical ports, this doesn't mean the USB bus is empty and silent.
When you connect to a server via BMC and request the console, you get two USB devices at least. One for mouse, one for keyboard. More devices appear if you attach virtual volumes remotely.
> Raid speed testing...
Because Linux kernel is stateless. There's no guarantee that you're booting on the same processor (make, model, family, even system bus layout) as the last boot. Moreover, there's no guarantee that you're not rebooting because of an unmaskable MCE which is fired because you lost half of your vector units (SSE/AVX blocks) or half of your FPU units, or any other CPU IP block (because you fried them) and you're in limp mode now...
I have seen tons of these events and similar ones first hand. I'll prefer my systems to spend three more seconds to boot successfully so I can debug them rather than the kernel makes some assumptions and catches fire in a completely unrecoverable state leaving me stranded.
Exactly! This is why Linux kernel does and shall ship with a configuration which supports everything out of the box, even if it's slow. Because it covers everyone's use cases that way.
If you need to trim it down to fit to your system(s), you should be able to do it. Debian has a mechanism called "Targeted Kernel" which removes the modules which won't be used on your system automatically during kernel upgrades.
Nobody is stopping you from doing whatever you want with your system to boot it faster.
For me, I'm fine with the Kernel as is, because some of my servers already take multiple minutes to initialize the plethora of devices on themselves. So a three second delay changes nothing on a system which is rebooted once a month at most.
Same applies to my desktop systems, which are either on or at S3 sleep, which wake in <3 seconds anyway (I wait for the monitor to come back mostly).
Everything is fine...
I prefer to have a resilient system in most cases, regardless of the form factor. If I was preparing an image for an embedded system, I'd go speed all the way down, within the limits of pragmatism.
I work in high performance computing. Speed is what we need, what we engineer for. However, resiliency is an equally important and valid concern. So, if I'm losing 5 seconds once a month (or once three-four months in case of desktop systems), that's a perfectly acceptable trade-off for a resilient system.
When a system tests its memory for 30 seconds, and initializes the motherboard and other devices for 3 minutes, losing 3 seconds on a bloody RAID speed test doesn't matter.
Oh, one of the latest servers we have exposes its management interface as a LAN port over USB, as I found out yesterday.
So, yeah.
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.
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.
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?
(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.
> You don’t allow access to the bootloader from any kernel, thereby afford a relative security in starting 2nd stage
You install and update the bootloader and its configuration from your running linux system.
In this new world, you would also update the kernel from your running linux system. That's the same, right? To update the kernel, you need to update bootloader configuration anyway, so it's obviously required that the running system can at least update the kernel, and that's true either way.
> Bricking (or worse, malicious kernel) seems more a possibility with upcoming Redhat design.
If your kernel is malicious, it's game over whether or not you're using grub, right? Like, that doesn't seem like a new threat model.
I don't really care about bricking because, frankly, I've made my system unbootable via grub bugs more often than I have through kernel bugs, and the kernel developers seem to take these bugs more seriously, so I feel like bricking is a possibility with either design, but less likely without grub.
Either way, I need to have a liveusb off to the side to fix these issues.
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.
I’ll look into this but prefer kernels managed automatically by apt/dnf etc.
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.
Probably slower and perhaps less compatible than using GRUB though.
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.
(or tell users to abandon all their use cases that led to the aforementioned complexity)
>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?
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.
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.
That's wrong, my laptop right now uses systemd-boot with a vmlinuz and an initramfs, no UKI. See a configuration example here: https://wiki.archlinux.org/title/Systemd-boot#Adding_loaders
I think my confusion here is that calling something "systemd-" because it's part of the group called systemd is tautological; anything that's independent could just as easily not be included in that group and not be called that. `nmbl` sounds like a piece of "core OS software", so why couldn't it be included in that group as well? It almost sounds like the only reason not to is to avoid naming confusion between multiple things in the "systemd group of software" that are boot-related, and that seems kind of silly.
To be clear, I'm not taking a pro- or anti-systemd in this thread; my concerns come from a place of pedantry around naming rather than anything technical. It just feels weird to me that the name "systemd-boot" could plausibly have been applied to either the bootloader or the "no-more-bootloader" if the other didn't exist, and I wish that things were named in a way that actually conveys using information rather than arbitrarily attaching confusing branding.
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.
I'm not sure about that.
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.
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).
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.
I wrote a guide on this topic of ensure platform integrity of system level (See https://wmealing.github.io/tpm-pcr07.html ) its not too hard.
Yup. I was just referencing wanting to obtain keys from the TPM to decrypt a partition. This is useful for me to have the following setup:
- Laptop turned on, no keys pressed, boots into super locked down guest OS.
- Laptop turned on, certain key pressed within 2 seconds, boot into 'hidden' OS.
- In both cases, HDD is encrypted, decrypted automatically via retrieving keys stored in the TPM. This means the harddrive cannot be read outside of that particular laptop, unless keys are extracted from the TPM.
- Bootloader signed with own key, any and all existing keys wiped, so laptop cannot be booted with any external OS.
How would I recreate that setup with nmbl?
That's a good link by the way, thanks - saved.
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)
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/...
Telling someone that they've "complained about a lot of things" or have "deliberately made this as hard as possible on [themselves]" is against HN's rules and guaranteed not to land well, regardless of how right you are or feel you are. Your comment would have been just fine without those bits.
If you wouldn't mind reviewing https://news.ycombinator.com/newsguidelines.html and taking the intended spirit of the site more to heart, we'd be grateful.
Whenever you feel like attacking someone else's reading ability, perhaps take a deep breath and remember this HN guideline:
> Be kind. Don't be snarky. Converse curiously; don't cross-examine. Edit out swipes.
Energy might be better spent explaining/defending the points you made. Similar to what the person you're replying to has been doing.
https://news.ycombinator.com/item?id=36316027 (June 2023)
https://news.ycombinator.com/item?id=36316001 (June 2023)
https://news.ycombinator.com/item?id=29959753 (Jan 2022)
https://news.ycombinator.com/item?id=28375317 (Sept 2021)
https://news.ycombinator.com/item?id=28375312 (Sept 2021)
https://news.ycombinator.com/item?id=28200716 (Aug 2021)
https://news.ycombinator.com/item?id=27157863 (May 2021)
https://news.ycombinator.com/item?id=26976826 (April 2021)
https://news.ycombinator.com/item?id=25129057 (Nov 2020)
We have to ban accounts that do this and I don't want to ban you, so if you'd please stop doing this, that would be good. Please stick to HN's rules no matter how provocative another commenter is being or you feel they are being.
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.
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?
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.