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




On 04/15/2017 05:24 AM, Brian wrote:
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?

During the first install of Debian to the SD card I allowed the installer to create a single partition filling the whole card. The primary purpose of that install was a brute force determination of whether or not my individual machine could read/write an SD card. The machine was a replacement for a different used machine purchased from the vendor. My accepting the SD card was dependent on that test.

I had reinstalled Debian to a more reasonably sized partition. That would explain a changed UUID. During the reinstall I experimented with installing grub to the MBR of the SD card. No grub was installed the first time.




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