Strange booting problem

[jd1008]

On 07/02/2015 12:02 PM, Chris Murphy wrote:
> On Thu, Jul 2, 2015 at 10:56 AM, Rick Stevens <ricks at alldigital.com> wrote:
>
>> Simply nulling bytes 510 and 511 of the first sector (getting rid
>> of the boot signature) should make the BIOS ignore the drive.
> That signature applies to the entire MBR, including the partition
> scheme. The signature is not a "boot me" signature.
>
> GRUB probably shouldn't honor that MBR as valid, including its
> partition scheme. I don't know if it does or not. The kernel won't,
> and therefore won't see the partitions, and neither will libblkid.
>
>
>
>   fdisk
>> will complain that the partition table is invalid because of the
>> invalid boot signature, but that's all. The rest of the drive should
>> be functional and usable--just not bootable.
> This is not correct.
>
>
>> Tagging a partition as "bootable" only affects Microsoft OSes.
> This is not completely correct. It depends on what boot code is in the
> MBR. GRUB boot.img doesn't use the active bit. But parted's code does,
> as does syslinux/extlinux.
>
>
I confirm  2 things:
1. the drive is indeed skipped
2. linux cannot see any partitions, so nothing gets mounted.