[conspire] debugging (and serial/net console ...)

[Michael Paoli]

2+ others I forgot to mention earlier:

serial console
net console

Essentially, if one has serial port (not via USB),
or network interface, one can do remote console to
another device/computer - and capturing that information
that way can be handy for debugging.  Most boot loaders
(e.g. grub/grub2) can also function over serial port (again, non-USB).

And the aforementioned serial, can also be virtual, if one is
working on troubleshooting/debugging a virtual machine.

And, depending on the nature of the issue(s) - particularly
if more so software and not hardware specific, sometimes taking
physical machine to virtual (or copy to virtual), and
poking/prodding/troubleshooting/debugging the virtual, etc.
can be quite handy.  E.g. not too many years back, I did that
for an issue on the linuxmafia.com host - got image copy of
the relevant data, brought that in to virtual environment,
used copy (keeping original copy as reference), and iteratively
worked out a "recipe" to fix the software issues - once that was
fully worked out and repeatedly tested on the virtual, applied
same to physical.

> From: "Michael Paoli" <Michael.Paoli at cal.berkeley.edu>
> Subject: Re: [conspire] debugging (and initramfs, and ...)
> Date: Sat, 09 Dec 2017 04:56:29 -0800

>> Message: 1
>> Date: Sat, 11 Feb 2017 19:40:57 +0000 (UTC)
>> From: Paul Zander <paulz at ieee.org>
>> To: Conspire List <conspire at linuxmafia.com>
>> Subject: [conspire] debugging
>> Message-ID: <1019574257.3572985.1486842057529 at mail.yahoo.com>
>> Content-Type: text/plain; charset=UTF-8
>>
>> I am running a desktop with Debian Testing and did an upgrade about  
>> 2 weeks ago.  Recently I have encountered a couple of "glitches"  
>> during boot up.  I can bring the various log files to cabal to  
>> examine, but which files?
>>
>> Glitch #1.   After grub, there is a message about "No Symbol  
>> Table".  I was going to manually record the exact words, but the  
>> warning timed out and proceeded.  I have successfully rebooted  
>> numerous times.
>>
>> Glitch #2.   After running a week or more, I decided to re-boot.   
>> The PC is dual-boot and there was something I couldn't do with  
>> Wine.  I made a point of closing all of the applications and  
>> windows before shutdown.  Later, during the re-boot of Debian, the  
>> boot screen froze with just three lines of text.  Lots of disk  
>> access, but several minutes on nothing on the screen.  I turned off  
>> power.  This morning
>
>> Message: 4
>> Date: Sat, 11 Feb 2017 15:54:00 -0800
>> From: Rick Moen <rick at linuxmafia.com>
>> To: conspire at linuxmafia.com
>> Subject: Re: [conspire] debugging
>> Message-ID: <20170211235400.GJ609 at linuxmafia.com>
>> Content-Type: text/plain; charset=utf-8
>>
>> Quoting Paul Zander (paulz at ieee.org):
>>
>>> 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.