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Re: Possibly erroneous "device not present" message during boot





Richard Owlett:
> On 04/12/2017 12:13 PM, Pascal Hambourg wrote:
>> Le 12/04/2017 à 17:14, Richard Owlett a écrit :
>>>
>>> Whether initiated after power-on OR a restart the observed sequence is:
>>> 1. Appearance of the Grub2 menu with a choice of 4 instances of Debian.
>>> 2. Select instance installed on the SD card.
>>> 3. Screen clears, this message appears against the Debian 8 background.
>>>    error:  no such device: 380e2a6d-f851-4fd1-9db2-869a0982b511.
>>>    Press any key to continue ...
>>> 4. Otherwise the instance of Debian on the SD card boots routinely.
>>
>> This is a GRUB error message which cannot find the UUID specified in a
>> "search" command.
>>
>> In order to investigate, can you
>> - report the menu entry code for the SD card system in
>> /boot/grub/grub.cfg (the one from the system on the hard drive owning
>> GRUB, not the one on the SD card) ;
> 
> On theory "too much better than too little" I see:
> <begin quote>
> ### BEGIN /etc/grub.d/20_linux_xen ###
> 
> ### END /etc/grub.d/20_linux_xen ###

Wild shot of the blind helping the half blind here.

If the uuid is correct but if sda and sdb are reversed the wrong
partition is found on the crossed uuid.
I couldn't reproduce it myself but there had been a couple of instances
while messing with usb-mem-sticks and installing grub to the stick as if
it was a real disk, that this happened.  Booting from the bios command
to choose between hdd or usb seemed more consistent than when bios was
adjusted to automatically try to boot from usb if it existed before
trying the hdd.  I don't know whether your setup can relate.  To make
matters worse when the usb installed grub was crossed and the hdd became
sdb I updated grub-pc which goes through the whole procedure of seeking
installed systems on all drives and updating the usb-installed grub to
where now it would seek hd installed systems in sdb!  So now the correct
booting order would not work and the default primary installed debian
was not found on sda1 as it did not exist on the hd.

So, I am speculating such crossing may have taken place between store
and home that produced the mistake, sda and sdb were reversed.  Now if
you have 1 hdd and 2 usb drives/mem-sticks things can get really messy
as grub is silly enough to think this is a fixed order of things.  As
you unplug sdb and reboot sdc has now become sdb even though it was
never moved.  But how did you install something on the usbdisk?  Was it
from a live usb-stick?  If that stick is gone then your installed grub
thinks that the HD is the usb/live stick that installed debian.

I hope this makes some sense to someone.  Does a usb memory stick really
have an MBR?  It may act like it.




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