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1y ago

Fedora 40 Eyes The Ability To Boot Unified Kernel Images Directly

www.phoronix.com Fedora 40 Eyes The Ability To Boot Unified Kernel Images Directly

23 comments

I am reminded of the ability MANY years ago to write the kernel file directly to a floppy disk, or start of a hard drive and somehow being able to boot that way.
I just can't recall how I did it, or WHY I did it.
Back when the kernel would fit on a floppy disk. I am truly showing my age.
6 yr old grandson found a box of old floppy disks and was asking what they were. He started stacking them up making card houses and roads for his matchbox cars. Glad he got some use out of those recycled AOL floppies.

This latest UKI work for Fedora will lead to better UEFI Secure Boot support, better supporting TPM measurements and confidential computing, and a more robust boot process.
and HOPEFULLY lead to a less jerky-flashy-switchy boot xperience, looks like a Vegas light show at present. switched to systemd-boot, but it's only a tiny bit better, still switches modes/blanks screen like five times.
- Mine only switches modes once, on load save backlight.
  
  yeah, if you don't have an encrypted drive (which I'm gonna do on a laptop NEVER) on some OEMs this can look semi-seamless.
  here's what it looks like on a laptop:
  OEM logo
  
  screen goes blank, backlight off
  
  light on, OEM logo
  
  blank screen
  
  decrypt password
  
  blank screen
  
  loading spinner with OEM logo
  
  gdm/sddm login screen
  
  blank screen
  
  9a. (sddm) loading animation
  9b. (sddm) jerk when fractional scaling kicks in
  and finally there's the desktop
  
  with additional mode switching interjected and occasionally the horror that is GRUB inserts a 'Loading blah blah' text message; thankfully we're getting rid of that.
- Omg yes, I hate those. I'm sitting here thinking it's probably one of those simple things that scares people away from Linux.."Oh god, I see black text on white background. Abort, abort, ABORT!!"

Is this good?
- It basically means instead of relying on a bootloader (e.g. GRUB or systemd-boot) the computer boots the kernel directly. Generally there should be no change besides having to use the BIOS menu to manually select a kernel.
  
  Thank you, you're awesome!
  
  Is the benifit making secure boot work better?
- Yes, in my opinion. The configuration of grub (boot loader) is just another step to go wrong, and this will eliminate that possibility. Additionally, it will prevent stupider operating systems (cough Windows) from accidentally overwriting the boot loader during an update.
  
  Does that mean that the OS would have to handle version booting?
- I think for most people they won't care either way.
  Some people do legitimately occasionally need to poke around in GRUB before loading the kernel. Setting up certain kernel parameters or looking for something on the filesystem or something like that. For those people, booting directly into the kernel means your ability to "poke around" is now limited by how nice your motherboard's firmware is. But even for those people, they should always at least have the option of setting up a 2-stage boot.

This is the best summary I could come up with:
Fedora 40 is eyeing the next phase of its unified kernel (UKI) support within the distribution that will include the ability to support booting to unified kernel image files directly without having to go through a traditional bootloader like GRUB or SD-Boot.
The second phase of Fedora's unified kernel support is looking at a boot path from the EFI SHIM to UKI directly without any bootloader present.
The UEFI boot configuration will get an entry for each kernel installed, newly-installed kernels are configured to be booted once but will then be made permanent after a successful boot, and also enabling UKI support for 64-bit Arm (AArch64).
This latest UKI work for Fedora will lead to better UEFI Secure Boot support, better supporting TPM measurements and confidential computing, and a more robust boot process.
Those interested in the latest UKI efforts for Fedora 40 can see this Fedora mailing list thread with more details.
The original article contains 153 words, the summary contains 153 words. Saved 0%. I'm a bot and I'm open source!

Is there not issues with filling up the NVRAM with efi entries, even if you're deleting old ones? I've bricked a computer by distrohopping so many times it couldn't write new entries.
- I'm probably wrong, but NVRAM suggests that there should be some way to clear it. (Clearing the CMOS might if you can't do it in software)
  
  I've cleared entries before with efibootmgr.

23 comments