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Re: BIOS Can Not Find Disk




On 12/01/2017 02:58 PM, Thomas Schmitt wrote:
Hi,

Dan Norton wrote:
# fdisk -l
...
Disklabel type: gpt
In the dim past, fdisk
could set a partition as "active", which was its euphemism for "bootable".
I guess, this applies only to MBR partition tables, not to GPT as on your
disk.

As Pascal stated, there is a bit defined in GPT to be the equivalent of
the "active" bit in MBR partitions. But it looks like "BIOS boot" in the
output of fdisk indicates a particular GPT partition type GUID.
Line 164 and 165 in
   https://github.com/karelzak/util-linux/blob/master/libfdisk/src/gpt.c
say
   	/* Hah!IdontneedEFI */
	DEF_GUID("21686148-6449-6E6F-744E-656564454649", N_("BIOS boot")),

Probably MBR code which will look for a boot indicator is not able to
interpret GPT.

Nevertheless, afaik GRUB installs an MBR which knows from where to get
its next program. So the question is rather how to install GRUB or repair
the existing installation. (Beyond my experience, i fear.)


Pascal Hambourg wrote:
- Partition attribute bit 2 = legacy BIOS bootable.
...
I just wonder how a BIOS would use that, though.
It's not the BIOS which reacts on the "active" bit. It's the MBR program
code which may or may not look for the bit. If it does, then it runs the
program code at the start of the partition.
Package "syslinux" has "mbr.bin" which is supposed to act that way:
   http://git.zytor.com/syslinux/syslinux.git/tree/mbr/mbr.S


OK, the syslinux and syslinux-efi packages are now installed and I'm studying man grub-install to see how to get the right mbr installed. It appears to be in /usr/lib/SYSLINUX-EFI/efi64. It is called syslinux.efi. Not sure this will cure the "ERROR:No boot disk..." problem tho.

 - Dan