Re: Install grub2 to ESP to boot to mmcblk0

[Toerless Eckert]

Thanks, Pascal for the answer, inline:

> Hello,
> 
> Le 17/09/2019 à 15:40, Toerless Eckert a écrit :
> > Notebook with one nvme with EFI: ESP and vendor OS. Would like to add
> > linux to a separate disk, but only option is mmcblk0 and PC bios can not 
> > boot from mmcblk0.
> 
> Is mmcblk0 an integrated eMMC module or a removable SD card ?

removable microSD card.

> > Trying to add grub2 to ESP and make it boot to linux on mmcblk0, but could 
> > not
> > find enough documentation how to make it work.
> > What i tried was to install debian onto mmcblk0p1, chroot into it,
> > mounted ESP onto /boot/efi, and ran grub-install --removable. This
> > created grubx64.efi in ESP, but when booting to it, i only got into grub
> > rescue.
> 
> Do you mean the ESP partition on the NVMe SSD ?

Yes. And i can boot that grubx64.efi, it just ends up in rescue mode.

> > Q: Anything that i could do in the grub rescue shell to figure out why
> > its not working ? ist storage devices found or the like ?
> 
> Yes : run the command "ls" to show which drives are made available by
> the UEFI firmware. If the firmware cannot boot from mmcblk0, chances are
> that it does not even care to make it available to the boot loader. If
> it shows only one drive (hd0), then I am afraid that the only solution
> is to put the whole /boot contents in the EFI partition or any other
> location on the NVMe SSD or any other bootable device such as a USB
> drive (if acceptable).

Yeah. Thats what i tried to avoid. I wanted to put as little as possible
onto the NVMe.

> > Q: Does grubx64.efi only rely on PC BIOS to find and read storage
> > devices, or does it have the option to include its own drivers (like a
> > linux kernel) to access storage type like mmcblk0 ?
> 
> By default, GRUB relies on the platform firmware but it can switch to
> native drivers with the command "nativedisk". Last time I used it with
> an ATA drive it was awfully slow. However I am not aware of a native
> SD/MMC driver. Use at your own risks.

Ok, let me check.

THanks again.