[conspire] debugging

[Rick Moen]

Quoting Paul Zander (paulz at ieee.org):

> My bad for not "asking a good question".
> 
> I had been ignoring the "no symbol table" message as not terribly
> important.  From your email, I understand that a messed up grub can
> compound to multiple problems.

True.  As is probably already clear, though, _only_ seeing a
missing-symbols diagnostic isn't such a problem.  (If you were intending
to diagnose a specific ELF module using the gdb debugger, its lack of
access to a symbols table would be a problem.  Otherwise, I cannot see
why.

The subsequent computer hang after that, _that_ qualifies as a problem
(as you yourself went on to say) -- but, of course, there you have the
issue that it was intermittent, so you cannot in any obvious way study
it afresh.

> So a very specific question, is there any log file I should capture
> that be helpful for diagnoses?

Alas, if you think about it, there's nothing capable of doing logging at
that moment, unless the bootloader itself does logging, which is a lot
to expect of a bootloader -- because nothing else is yet running.

Until the OS kernel and an init process and the root filesystem are
loaded, you cannot reasonably expect logging to commence, and that is
when it does on all systems of my acquaintance.

Probably a more useful question if you need to debug a GRUB2
installation is 'How do I do step-by-step debugging of my GRUB2 
boot system?'

Web-searching

   grub2 debug

brings up quite a lot of links including a GNU GRUB 2 Debugging with
GDB HOWTO.  (Of course -- and maybe I am a Bad Person for laughing, here
-- if the missing symbols problem is being produced by a GRUB2 module, 
it would inherently be kinda difficult to debug using gdb, for lack of a
symbols table.  Absence of chicken, meet absence of egg.  Shake.)

The FSF manual for GRUB2 offers
https://www.gnu.org/software/grub/manual/grub.html#Troubleshooting , 
which is of only limited help.  I don't see anything about GRUB2 having
logging abilities.
Ubuntu's Community Wiki offers 
https://help.ubuntu.com/community/Grub2/Troubleshooting
(I note that the wiki page mentions that GRUB2 does a certain amount of
self-healing.  Maybe that's what caused your initial symbols symptom to
automagically vanish.  Dunno; insufficient data.)

ArchLinux offers 
https://wiki.archlinux.org/index.php?title=GRUB#Troubleshooting

It's always been difficult to solve problems early in startup because
there's not a _lot_ of opportunity to say 'Whoa, will you wait there a
minute?' 

The more you know about a bootloader's controls, the more you are able
to assert a _small_ degree of control, e.g., turning off the bullshit
'splash screen' so you have some hope of seeing what's going on.


> Last comment: We have previously discussed dual boot at great length.
> This is the first time that I have had a problem with grub.  Maybe I
> have been lucky these many years.  And UEFI is phasing (or forcing)
> grub out for new installations.

Well, I don't see why it should be.
https://wiki.archlinux.org/index.php?title=GRUB#UEFI_systems
https://wiki.archlinux.org/index.php?title=GRUB#UEFI

If I understand correctly, efibootmgr modifies UEFI firmware boot
manager variables appropriately to let GRUB work in that environment
(by creating 'bootable .efi stub entries', whatever that means).

> BTW, regarding back-up.  I am glad that my /home and /data directories
> are in separate partitions.  If I have to reinstall Linux, my personal
> files might possibly survive without restoring from backup.

Definitely a help.  Personally, what really makes _me_ sleep easier 
at night is a big detechable USB external hard drive, that is normally
stored distantly from the machine in question.