[Buildroot] Grub2 on x86_64 build works in VM, but not on target

[Jimmy at 86Pixels]

I think this actually just has to do with drive reordering. Once I
reference the drive by UUID it seems to work!

So for future reference, Googlers, try referencing your drive in grub
(the root= param in the kernel line) by the drive's UUID identified by
the command 'blkid' on the disk.

Best,
Jimmy

On Thu, Jun 8, 2017, at 06:33 AM, Jimmy at 86Pixels wrote:
> Good morning all,
> 
> I've got a question here that has had me stumped for a bit.  I'm
> targeting the pc_x86_64 platform, and the build and everything finishes
> perfectly, and I'm able to run my disk.img in QEMU and get the grub
> screen, and subsequently boot into the OS using the -hda argument.  I
> then flash disk.img (auto generated by buildroot) to a SATA SSD and the
> kernel eventually panics because it can't mount the rootfs. Everything
> is at default settings, so root is set to /dev/sda1.  Grub2 detects the
> drive as (hd0,msdos1), and I'm able to read the contents of the
> drive/partition from grub.
> 
> The error is Unable to mount root fs on unknown block (8,1): error -6. 
> The boot screen DOES seem to be detecting sda, and again, I can read its
> contents from the grub command line.
> 
> I realize this is a question straddling grub vs. buildroot support, but
> I didn't know if any of you had seen anything similar using buildroots
> default configurations for this particular target, or if this was a
> known issue.
> 
> Thank you so much in advance! Any pointers are appreciated.
> 
> Jimmy