[Solved] VFS: cannot open root device, unknown-block(0,0)

[nkostovsky]

Hi, I'm new in gentoo and I'm trying to boot kernel directly from UEFI.

I was able to run gentoo with grub/efi/initramfs(?), now I'd like to save a couple of seconds on booting gentoo (trying that for about a day) by skipping grub step.

But I'm getting an error when trying to boot bzImage from uefi (as well as from grub) (photo: https://imgur.com/a/VOxvTeS):

/dev/root: Can't open blockdev
VFS: cannot open root device "/dev/nvmen1p3", unknown-block(0,0): error -6

Could please anyone tell what could be wrong in my setup?

What I tried to achieve that (actually I was trying to reproduce this setup found on the internet - https://handheld.computer/?page_id=1131, as well as gentoo guides like uefi_stub - https://wiki.gentoo.org/wiki/EFI_stub):

Laptop: one netbook a1 pro

configured kernel - https://wiki.gentoo.org/wiki/Project:Distribution_Kernel#Modifying_kernel_configuration

[bstaletic]

Your NVMe drivers are modules, so you need the initramfs.
Yet you did not specify the initramfs for your EFI boot entry.

https://wiki.gentoo.org/wiki/Efibootmgr#Configuration

[nkostovsky]

thanks for reply

[bstaletic]

I'm booting without an initramfs, so it's definitely possible.

For that, you need a few things:

• root=/dev/whatever_partition in your kernel command line.
  
• The filesystem drtiver built into the kernel.
  
• The NVMe controller driver built into the kernel.
  

From the output of your lspci:

[pietinger]

Nikita Kostovsky,

first of all: Welcome to Gentoo Forums!

Please dont use our Gentoo distribution kernel if you want to configure your kernel manually. For this use only our package sys-kernel/gentoo-sources.

If you dont want an initramfs (I completely understand) you MUST configure everything the kernel needs to access its root partition INTO the kernel statically and NOT as module ... but you will see it all in my articles ...

I am booting also my manually configured kernel via UEFI directly and I highly suggest to read all these articles:

https://wiki.gentoo.org/wiki/User:Pietinger/New_at_Gentoo

https://wiki.gentoo.org/wiki/User:Pietinger/Tutorials/Manual_kernel_configuration

https://wiki.gentoo.org/wiki/User:Pietinger/Tutorials/Boot_kernel_via_UEFI

( https://wiki.gentoo.org/wiki/User:Pietinger/Tutorials/Initramfs_Overview )
_________________
https://wiki.gentoo.org/wiki/User:Pietinger

[sublogic]

@Nikita: one way to bootstrap your way into a working kernel:

1. Install a distribution kernel (sys-kernel/gentoo-kernel). Finish the handbook.
   
2. Install sys-kernel/gentoo-sources. Update the /usr/src/linux link (eselect kernel).
   
3. make localyesconfig
   
4. make menuconfig
   
5. make, make modules_install, make install

That sould give you a kernel that boots. You can tweak it later as needs arise.

Step 3 converts the drivers loaded at the time to builtin, and drops all the others.
At step 4, you want to turn some of them back to modular, and maybe add back some that were dropped. Anything that needs firmware, like a wireless driver, is best kept as modular (unless you absolutely need it at boot time, in which case embed its firmware). Also, add back dropped drivers that you might need later (like usb-storage).

Proceed in stages and compare configs with the scripts/diffconfig tool in the kernel tree. In my cases there were more changes at step 4 than I expected. I can elaborate if you want.

[nkostovsky]

thanks to all of you, i will try to read all of this and use/reconfigure gentoo-sources from scratch to do it right

[pietinger]

sublogic,

there are now some cases where the procedure with “make localyesconfig / make localmodconfig” no longer works because the default config does not contain some important options. An example: Some (modern) mainboards ONLY accept x2APIC and therefore need to have CONFIG_X86_X2APIC enabled to boot, which unfortunately is not enabled in the default config (see this thread: https://forums.gentoo.org/viewtopic-t-1171781-highlight-.html ). Likewise, some mainboards also require CONFIG_X86_INTEL_LPSS, which is also not activated in the default config. This is the reason why I ALWAYS refer to my articles that address both and why I NEVER recommend the above (outdated) procedure (which CAN still work, of course) - but this way you are on the safe side.
_________________
https://wiki.gentoo.org/wiki/User:Pietinger

[pietinger]

Nikita Kostovsky,

I would like to give you the tip to install kernel version 6.12 right away.
_________________
https://wiki.gentoo.org/wiki/User:Pietinger

[sublogic]

[pietinger]

[nkostovsky]

[pietinger]