Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

No more boot loader: Please use the kernel instead

pretalx.com

Post reply on HN
Print view View original

71–80 of 460 posts

Re: No more boot loader: Please use the kernel instead

#71

Post by ars »

benwaffle wrote: post #47
andrewstuart wrote: post #11

I’m fairly technical but I have to say grasping the field of partitions , booting, boot loaders grub uefi its alternatives and the various combinations thereof in Linux defeated me. When learning something I try to find the simple path, a reliable minimum that gets to the goal. I never found it. Complexity is the word that comes to mind.

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

The simplest is LILO without an initrd

Re: No more boot loader: Please use the kernel instead

#72

Post by Arnavion »

fsniper wrote: post #27

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

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

Re: No more boot loader: Please use the kernel instead

#73

Post by zamadatix »

Spivak wrote: post #58
fsniper wrote: post #27

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

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

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

Re: No more boot loader: Please use the kernel instead

#74

Post by drewg123 »

ta8645 wrote: post #7
drewg123 wrote: post #2

I personally think they're moving in the wrong direction. I'd rather have "NMIRFS" (no more initramfs). Eg, a smarter bootloader that understands all bootable filesystems and cooperates with the kernel to pre-load modules needed for boot and obviates the need for initramfs. FreeBSD's loader does this, and its so much easier to deal with. Eg, it understands ZFS, and can pre-load storage driver modules and zfs.ko for t…

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

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

Re: No more boot loader: Please use the kernel instead

#75

Post by mlyle »

aaronmdjones wrote: post #18
drewg123 wrote: post #2

I personally think they're moving in the wrong direction. I'd rather have "NMIRFS" (no more initramfs). Eg, a smarter bootloader that understands all bootable filesystems and cooperates with the kernel to pre-load modules needed for boot and obviates the need for initramfs. FreeBSD's loader does this, and its so much easier to deal with. Eg, it understands ZFS, and can pre-load storage driver modules and zfs.ko for t…

As other sibling comments have explained, an initramfs is usually optional for booting Linux. If you build the drivers for your storage media and filesystem into the kernel (not as a module), and the filesystem is visible to the kernel without any userland setup required beforehand (e.g. the filesystem is not in an LVM volume, not on an MD-RAID array, not encrypted), it is fully capable of mounting the real root file…

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

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

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

Re: No more boot loader: Please use the kernel instead

#76

Post by throwway120385 »

alerighi wrote: post #45

It's something you can do since a lot of years. I used to do so 10 years ago, when I've got the first motherboard with UEFI. But is it useful? It saves a minimal time in the boot sequence, but at what cost? The bootloader (being it grub, or something more simple as systemd-boot) is useful to me for a couple of reasons: - it allows to dual-boot with Windows easily: motherboard boot menu is often not easy to access, yo…

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

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

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

Re: No more boot loader: Please use the kernel instead

#77

Post by saghm »

Arnavion wrote: post #41
saghm wrote: post #32

Earlier quoted context omitted.

Right before that paragraph, they cite issues with GRUB as a motivation for this work. What confuses me is that Redhat already has a GRUB replacement in systemd-boot. Is this work intended to obviate that as well, or is it going to relate to it somehow? I imagine doing all this and tying it to systemd would generate some backlash like usual (although at this point, it seems unlikely that this would affect the plans g…

>I imagine doing all this and tying it to systemd would generate some backlash like usual (although at this point, it seems unlikely that this would affect the plans given how few distros don't use systemd). systemd-boot is independent of systemd. It's called "systemd-" because it's under the same "group of core OS software" umbrella named "systemd", but otherwise it can be compiled independently, does not require th…

> 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.

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.

Re: No more boot loader: Please use the kernel instead

#78

Post by vlovich123 »

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

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

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

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

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

Re: No more boot loader: Please use the kernel instead

#79

Post by Denvercoder9 »

alerighi wrote: post #45

It's something you can do since a lot of years. I used to do so 10 years ago, when I've got the first motherboard with UEFI. But is it useful? It saves a minimal time in the boot sequence, but at what cost? The bootloader (being it grub, or something more simple as systemd-boot) is useful to me for a couple of reasons: - it allows to dual-boot with Windows easily: motherboard boot menu is often not easy to access, yo…

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

Re: No more boot loader: Please use the kernel instead

#80

Post by mjg59 »

Denvercoder9 wrote: post #79
alerighi wrote: post #45

It's something you can do since a lot of years. I used to do so 10 years ago, when I've got the first motherboard with UEFI. But is it useful? It saves a minimal time in the boot sequence, but at what cost? The bootloader (being it grub, or something more simple as systemd-boot) is useful to me for a couple of reasons: - it allows to dual-boot with Windows easily: motherboard boot menu is often not easy to access, yo…

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

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