Web lists-archives.com

Re: BIOS Can Not Find Disk




On 12/03/2017 06:49 AM, Felix Miata wrote:

Pascal Hambourg composed on 2017-12-03 10:49 (UTC+0100):

Felix Miata composed:
...
So I guess that the OP means that the core image of GRUB is in sda1, and
the boot image of GRUB is in the MBR of sda.
  Based on OP's response to

https://lists.debian.org/debian-user/2017/11/msg00563.html

in

https://lists.debian.org/debian-user/2017/11/msg00935.html

I'm pretty sure that was not OP's intent, i.e., none of Grub at all in MBR.

Yes, no grub in mbr - unless installer insists.


...
The option the OP chose is to intervene ab initio. When Grub is installed to an
MBR primary partition, and the MBR contains legacy boot code, and a boot flag is
appropriately set, and the same policy is maintained, a subsequent installation
makes no attempt to usurp control from the first.
That does not match my experience. A subsequent installation does not
care about what kind of boot code is in the MBR nor whether a boot flag
is set....
  Grub does not care about boot flags, but when depending on legacy (neutral[1])
MBR code to locate the partition from which to boot, as was the apparent plan by
the OP, it's crucial.

The installers of most Linux distros default to installing Grub to the MBR. Some
make it difficult to determine whether any other option even exists. It's been
several months since I last installed Stretch. I don't remember how it presents
bootloader installation location, or more importantly, if when partition is
selected on a device with no installed operating systems, a separate action is
required to ensure the MBR contains any boot code at all.

[1]
<https://old-en.opensuse.org/Bugs/grub#How_does_a_PC_boot_.2F_How_can_I_set_up_a_working_GRUB.3F>

FWIW, this done just now:

# gdisk /dev/sda
GPT fdisk (gdisk) version 0.8.10

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with protective MBR; using GPT.

Command (? for help): b
Enter backup filename to save: mbrforgpt
The operation has completed successfully.

Command (? for help): q

# ls -l mbr*
-rw-r--r-- 1 root root 17920 Dec  4 05:47 mbrforgpt

# mc -v mbrforgpt
The above shows 0x55AA at +0x1FE (Boot signature [1]).
Also, the search for 'ERROR:' is not found in the entire 17920 bytes of file mbrforgpt.

[1] https://en.wikipedia.org/wiki/Master_boot_record

Apparently, all is in readiness. It's simply that this PC is not loading the mbr or anything else from sda. Any other opinions?