On Wed, May 8, 2019, 4:50 AM Panu Matilainen <pmati...@redhat.com> wrote:

>
>
> Nicolas' point is that the rescue boot entry only works in a limited
> number of scenarios.
>

I'm not sure which of three 'rescue' options is being discussed.

grub rescue appears when normal.mod can't be loaded, and means the menu
can't be displayed. This thread's bug results in this rescue.

Since circa Fedora 19, there is a GRUB menu entry 'Rescue' option which
boots a "no host only" initramfs. If you see the option, you don't have the
bug under discussion.

Install media, dvd and netinst, have a bootloader submenu option for
Troubleshooting, that leads to an option Rescue a Fedora system, which
actually launches anaconda with app option 'inst.rescue' that helps find,
assemble and mount a Fedora installation or even just provide a shell with
all the CLI programs normally available for installs including fsck, mkfs,
various FS debug tools, etc.




> And in some cases the rescue media IS needed to fix this particular
> issue as well. For example my box never got to the grub prompt at all,
> it was busy reboot-looping, probably due to negletting to reinstall grub
> in almost a decade. Others have pointed out other "completely broken"
> symptoms.
>

I don't think that's this bug. It suggests the core.img embedded in either
the MBR gap or BIOSBoot partition has a serious bug or that the computer
firmware has a serious bug. Somehow is can neither load blscfg.mod (this
bug) and can't run it's own rescue mode (not this bug).

That would be super tedious to track down. And interestingly, would
potentially be masked by always updating the bootloader between major
upgrades (makes bootloader a moving Target). But if no one ever tracks it
down, which includes the even more tedious requirement of localy building
GRUB from source and reproducing the bug (because Fedora's GRUB is so
substantially modified from upstream that upstream will always reject
Fedora bugs), it won't get fixed.

I admit, we've already failed if we're at grub rescue, letter alone in a
reboot cycle. But the latter sounds hardware (firmware) specific. Difficult
no matter what.



> Really, if you don't even get a menu from grub, how many people are
> going to be able to work it from there?


I think 1 in 10. Just a guess. That's probably generous.



Even if there was another
> computer comfortably nearby for googling, I wouldn't bother even trying.
> Much easier to grab that rescue image, which thank goodness is there still.


I don't know what rescue image is.

The bug this thread is about, if you hit it, you do not get a GRUB menu.

To me, rescue image means install media with Rescue boot option i.e.
anaconda inst.rescue.


--
Chris Murphy
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