F27 boots to grub> after (failed?) dnf update ?

[linux guy]

I ran DNF update via ssh on my x86_64 FC27 server the other day. For some
reason it didn't finish and when I rebooted it, it boots to a grub prompt.

"Minimal BASH-like line editing..." grub>

So...

grub> set root=(lvm/fedora/root)
grub> linuxefi (hd0,gpt2)/linuz-4.14.13-300.fc27.x86_64
grub>initrdefi (hd0,gpt2)/initramfs-4.14.13-300.fc27.x86_64.img
grub>boot

This gives me a switch root error and stops at the emergency mode prompt #.

How do I get my server to boot again ?

Thanks

[linux guy]

I also did this, to no avail.

mkdir temproot
mount /dev/fedora/root temproot
cd temproot
mount /dev/sda2 boot
mount --bind /dev temproot/dev
mount --bind /proc temproot/proc
mount --bind /sys temproot/sys
chroot temproot
grub2-mkconfig -o /boot/grub2/grub.cfg
​

[Samuel Sieb]

On 03/26/2018 09:14 AM, linux guy wrote:
> "Minimal BASH-like line editing..." grub>
>
> So...
>
> grub> set root=(lvm/fedora/root)
> grub> linuxefi (hd0,gpt2)/linuz-4.14.13-300.fc27.x86_64
> grub>initrdefi (hd0,gpt2)/initramfs-4.14.13-300.fc27.x86_64.img
> grub>boot
>
> This gives me a switch root error and stops at the emergency mode prompt #.

You're missing all the parameters to the kernel that tell it where the 
root is.
> How do I get my server to boot again ?

From your other email:
> grub2-mkconfig -o /boot/grub2/grub.cfg

That's the wrong place for an EFI system.  You need to mount the EFI 
partition (probably /dev/sda1 in your case) at /boot/efi and the 
grub.cfg is in /boot/efi/EFI/fedora/.

[linux guy]

Thanks for the reply.

I thought that "set root=(lvm/fedora/root)" told the boot process where
root was.  Where is this stuff documented ?

So I should add something like "root=/dev/mapper/fedora-root" to the
Linuxefi line ?  Do I need anything else to get a minimal system running ?

On Mon, Mar 26, 2018 at 4:38 PM, Samuel Sieb  wrote:
> On 03/26/2018 09:14 AM, linux guy wrote:
> > "Minimal BASH-like line editing..." grub>
> >
> > So...
> >
> > grub> set root=(lvm/fedora/root)
> > grub> linuxefi (hd0,gpt2)/linuz-4.14.13-300.fc27.x86_64
> > grub>initrdefi (hd0,gpt2)/initramfs-4.14.13-300.fc27.x86_64.img
> > grub>boot
> >
> > This gives me a switch root error and stops at the emergency mode prompt
> > #.
>
> You're missing all the parameters to the kernel that tell it where the
> root is.
>
> How do I get my server to boot again ?
> >
>
> From your other email:
> > grub2-mkconfig -o /boot/grub2/grub.cfg
>
> That's the wrong place for an EFI system.  You need to mount the EFI
> partition (probably /dev/sda1 in your case) at /boot/efi and the grub.cfg
> is in /boot/efi/EFI/fedora/.
> _______________________________________________
> users mailing list -- [e-mail]
> To unsubscribe send an email to [e-mail]

[Samuel Sieb]

On 03/26/2018 07:16 PM, linux guy wrote:
> Thanks for the reply.
>
> I thought that "set root=(lvm/fedora/root)" told the boot process where 
> root was.  Where is this stuff documented ?

That command is to tell grub where to find files.
> So I should add something like "root=/dev/mapper/fedora-root" to the 
> Linuxefi line ?  Do I need anything else to get a minimal system running ?

That's probably enough.

[linux guy]

Thanks for the reply.

This allowed me to boot my system to a working KDE session:

grub> set root=(lvm/fedora/root)
grub> linuxefi (hd0,gpt2)/linuz-4.14.13-300.fc27.x86_64
root=/dev/mapper/fedora-root
grub>initrdefi (hd0,gpt2)/initramfs-4.14.13-300.fc27.x86_64.img
grub>boot
​
I ran "grub2-mkconfig  -o /boot/efi/EFI/fedora/grub.cfg" and it seemed to
generate a valid grub.cfg file.  Do I need to do anything else to utilize
that file, like a grub2-install ?   https://fedoraproject.org/wiki/GRUB_2

[Samuel Sieb]

On 03/26/2018 09:56 PM, linux guy wrote:
> I ran "grub2-mkconfig  -o /boot/efi/EFI/fedora/grub.cfg" and it seemed 
> to generate a valid grub.cfg file.  Do I need to do anything else to 
> utilize that file, like a grub2-install ? 
> https://fedoraproject.org/wiki/GRUB_2

That's all.  With EFI, you don't have to install to the boot sector.

[linux guy]

Thanks !

[Chris Murphy]

On Mon, Mar 26, 2018, 10:15 AM linux guy  wrote:
> I ran DNF update via ssh on my x86_64 FC27 server the other day. For some
> reason it didn't finish and when I rebooted it, it boots to a grub prompt.
>
> "Minimal BASH-like line editing..." grub>

Sounds like this bug (long)
https://bugzilla.redhat.com/show_bug.cgi?id=1227736

Short version, boot any Fedora install media and simply mount the
filesystem containing /boot. Then just reboot.

Ahhh except this is UEFI so no you have a different problem maybe. Your
grub.cfg is on /boot/efi unless you've got a non-standard installation. And
this is a FAT volume. I'm not really sure what's happened, but the easiest
is boot netinstall or server DVD and choose the troubleshooting>rescue
option. This will assemble the system and now you can chroot and run the
usual grub2-mkconfig command for EFI systems.

grub> prompt on UEFI usually means the grub.cfg is not found, empty, or
mangled.
> So...
>
> grub> set root=(lvm/fedora/root)
> grub> linuxefi (hd0,gpt2)/linuz-4.14.13-300.fc27.x86_64
> grub>initrdefi (hd0,gpt2)/initramfs-4.14.13-300.fc27.x86_64.img
> grub>boot
>
> This gives me a switch root error and stops at the emergency mode prompt #.
>
> How do I get my server to boot again ?

Need logs.
> Thanks
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> users mailing list -- [e-mail]
> To unsubscribe send an email to [e-mail]