How do I regenerate the grub files for a UEFI system ?

[linux guy]

How do I regenerate the grub files for a UEFI system to boot from ?

Thanks

[linux guy]

Also, what files and symlinks need to be in place for grub to boot on an
UEFI system.

(I'm trying to get a non booting UEFI system booting again.)

On Wed, Jun 5, 2019 at 2:04 PM linux guy  wrote:
> How do I regenerate the grub files for a UEFI system to boot from ?
>
> Thanks

[Ted Roche]

On Wed, Jun 5, 2019 at 4:05 PM linux guy  wrote:
> How do I regenerate the grub files for a UEFI system to boot from ?

This might help: https://fedoraproject.org/wiki/GRUB_2

[stan]

On Wed, 5 Jun 2019 14:05:39 -0600
linux guy  wrote:
> Also, what files and symlinks need to be in place for grub to boot on
> an UEFI system.
>
> (I'm trying to get a non booting UEFI system booting again.)
>
> On Wed, Jun 5, 2019 at 2:04 PM linux guy 
> wrote:
> > How do I regenerate the grub files for a UEFI system to boot from ?
> >
> > Thanks

I have no experience with this, but since I am having problems with a
UEFI install, and will probably have this problem at some point, I
decided to do a search, and found this. It's a few years old, but
*should* at least get you started.

https://superuser.com/questions/596317/how-would-i-reinstall-the-grub-efi-bo...

[stan]

On Wed, 5 Jun 2019 16:16:25 -0400
Ted Roche  wrote:
> On Wed, Jun 5, 2019 at 4:05 PM linux guy 
> wrote:
> > How do I regenerate the grub files for a UEFI system to boot from ?
>
> This might help: https://fedoraproject.org/wiki/GRUB_2

Much better than my answer.  Thanks, saved for future reference.

[linux guy]

When I get to step #8 (grub2-install --boot-directory=/boot /dev/sda) on
this page (
https://fedoraproject.org/wiki/GRUB_2#Create_a_GRUB_2_configuration), it
fails with a can't find efi directory error.

What am I doing wrong ?

Should this work to boot my computer from the grub command prompt ?

set root=(hd0,gpt6)
set prefix=(hd0,gpt6)/boot/grub

insmod normal
normal

I've been booting it another, longer way.

[linux guy]

FWIW, I can boot the computer from the grub prompt with this.

grub> set root=(lvm/fedora/root)
rub> ls (hd0, gpt2)/
grub> linuxefi (hd0,gpt2)/linuz-4.14.13-300.fc27.x86_64
root=/dev/mapper/fedora-root
(or the rescue kernel)
grub>initrdefi (hd0,gpt2)/initramfs-4.14.13-300.fc27.x86_64.img
grub>boot

#ls /system/call/net   Find Ethernet adapter.   In may case it was enp3s0
#ifup enp3s0

On Wed, Jun 5, 2019 at 4:28 PM linux guy  wrote:
> When I get to step #8 (grub2-install --boot-directory=/boot /dev/sda) on
> this page (
> https://fedoraproject.org/wiki/GRUB_2#Create_a_GRUB_2_configuration), it
> fails with a can't find efi directory error.
>
> What am I doing wrong ?
>
> Should this work to boot my computer from the grub command prompt ?
>
> set root=(hd0,gpt6)
> set prefix=(hd0,gpt6)/boot/grub
>
> insmod normal
> normal
>
> I've been booting it another, longer way.

[Chris Murphy]

On Wed, Jun 5, 2019 at 4:35 PM linux guy  wrote:
> When I get to step #8 (grub2-install --boot-directory=/boot /dev/sda) on this page (https://fedoraproject.org/wiki/GRUB_2#Create_a_GRUB_2_configuration), it fails with a can't find efi directory error.
>
> What am I doing wrong ?

That command is for computers with BIOS firmware. It's the wrong
command for computers with UEFI firmware.

And to make things a bit more confusing, it matters what version of
Fedora you're using as there have been changes in Fedora 30.

What you originally asked for is how to "regenerate" grub files, which
is somewhat vague what you're really after. There are many grub files
and they aren't all put where they are the same way. You're better off
telling us what the problem is, exactly, otherwise this is a spaghetti
on the wall approach to solving the problem.
> Should this work to boot my computer from the grub command prompt ?
>
> set root=(hd0,gpt6)
> set prefix=(hd0,gpt6)/boot/grub
>
> insmod normal
> normal
>
> I've been booting it another, longer way.

There's no way for anyone to confirm or deny that should work because
we have no idea what your GRUB thinks the physical device and
partition for the GRUB root and prefix should be. That's pretty deep
in the weeds.

You're best off explaining what you did just prior to the problem, and
describe the problem in terms of what does happen and what you expect
should happen instead (i.e. I can't boot, is not descriptive enough).

[Chris Murphy]

On Wed, Jun 5, 2019 at 4:48 PM linux guy  wrote:
> FWIW, I can boot the computer from the grub prompt with this.
>
> grub> set root=(lvm/fedora/root)
> rub> ls (hd0, gpt2)/
> grub> linuxefi (hd0,gpt2)/linuz-4.14.13-300.fc27.x86_64 root=/dev/mapper/fedora-root   (or the rescue kernel)
> grub>initrdefi (hd0,gpt2)/initramfs-4.14.13-300.fc27.x86_64.img
> grub>boot

OK on Fedora 27 you can follow the UEFI reinstall steps here:

https://fedoraproject.org/wiki/GRUB_2#Updating_GRUB_2_configuration_on_UEFI_...

Simplified, that's:

dnf reinstall grub2-efi shim
grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg