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




On Fri 14 Apr 2017 at 13:33:40 -0500, Richard Owlett wrote:

> On 04/14/2017 12:24 PM, Brian wrote:
> >
> >Everything GRUB knows about devices comes from what the BIOS tells it.
> >They are more than just good friends. :)
> >
> >It appears from 'ls' at a GRUB prompt that your GRUB does not know about
> >your SD card. Booting takes place but GRUB takes its time to think about
> >what it should do about not finding something it has been told to search
> >for. In the end, it decides to go ahead, but in some cases it wouldn't.
> >That would dispel your present mood of happiness.
> >
> >While we are it it: your update-grub stanza does not contain a line with
> >set root=" in it. Could this possibly be a copy and paste error? I ask
> >because the line is present on Jessie and testing when the device is a
> >USB stick.
> 
> Just to eliminate any source of copy errors, here is the full contents of
> grub.cfg created just prior to my most recent post
> (https://lists.debian.org/debian-user/2017/04/msg00468.html). It refers to
> the 2 new installs I mentioned in that post.

Thank you.

> ### BEGIN /etc/grub.d/30_os-prober ###
> menuentry 'Debian GNU/Linux (8.6) (on /dev/mmcblk0p1)' --class gnu-linux
> --class gnu --class os $menuentry_id_option
> 'osprober-gnulinux-simple-e57b2c64-74ec-4184-af71-d807e07f07dd' {
> 	insmod part_msdos
> 	insmod ext2
> 	if [ x$feature_platform_search_hint = xy ]; then
> 	  search --no-floppy --fs-uuid --set=root
> e57b2c64-74ec-4184-af71-d807e07f07dd
> 	else
> 	  search --no-floppy --fs-uuid --set=root
> e57b2c64-74ec-4184-af71-d807e07f07dd
> 	fi
> 	linux /boot/vmlinuz-3.16.0-4-686-pae
> root=UUID=e57b2c64-74ec-4184-af71-d807e07f07dd ro quiet
> 	initrd /boot/initrd.img-3.16.0-4-686-pae
> }

Definitely no "set root=" line. We will have to give GRUB credit for
knowing what it is doing. The absence of this line probably accounts for
your previous successful booting. With such a line you would possibly
have got "cannot get C/H/S values" as an error message. This throws
booting back to the GRUB menu.

Now for a big "but". :)

Your previous 'Debian GNU/Linux (8.6) (on /dev/mmcblk0p1)' stanza had

 linux /boot/vmlinuz-3.16.0-4-686-pae root=/dev/mmcblk0p1

This one has

 linux /boot/vmlinuz-3.16.0-4-686-pae root=UUID=e57b2c64-74ec-4184-af71-d807e07f07dd ro quiet

The UUID has changed (I think you said you had done this) but the kernel
now looks for init using the UUID rather than on /dev/mmcblk0p1. How did
you manage to get something significantly different?

And, more to the point, is there booting from the card without any error
messages?

-- 
Brian.