I have been able to successfully read and write all data on my 3TB sata hdd on UdooX86. This hdd gets listed under legacy devices in BIOS. But I have not been able to boot from it. This hdd has protective mbr with gpt partition created using gparted. Debian stretch is installed in 5th partition and grub2 is installed on that disk. Two other x86 motherboards can boot debian from same hdd in legacy mode. But when UdooX86 boots that hdd in legacy mode, I do not see grub2. Instead, I see blinking cursor indefinitely. Is there anything I can try out here? I have also installed Debian stretch on UdooX86 emmc. I am fine if grub on emmc will be able to boot debian on hdd. It is not working as well. If I goto grub2 command prompt, I get following problem. grub> ls hd0 (hd0,msdos1) hd1 ((hd0 is emmc and hd1 is sata hdd.)) grub> insmod part_gpt grub> ls ((Here system hangs indefinitely. It is expected to show gpt partitions on this hdd.))
Did you install Debian Stretch to eMMC in legacy or EFI mode? I don't understand this that well, but installing EFI mode OS might be a problem when trying to boot from legacy device.
Installed debian to eMMC in legacy mode. It is booting fine. But I want to boot debian on my sata hdd. When I attached sata, Grub2 on eMMC detected debian on sata and created new entry for that. If I select this entry, system hangs. I found it hangs when it first tries to use gpt partition. Commands in my last post reproduce it.
I did quick installation of debian in another partition of 3TB sata and it is booting fine. This partition is at the beginning of hdd. I checked which all partitions are showing data in grub prompt(using set root=hd0,sdaX ; ls / ). Found something amazing. sda1, sda7, sda2 and sda3 are showing their data. These are all located at the beginning of the disk. Grub2 hangs while showing data on sda4, sda5, sda6. They all reside at the end of disk. Partition sda5 was the one I was trying to boot from since beginning. Installation in this partition did not boot at all. But Installation on sda3 worked fine. This problem was not there in two other x86 motherboards I used. This leads to conclusion. There is something wrong with UdooX86's legacy mode accessing data on disk, located at the end of disk(maybe after 2TB). Is anybody facing this problem? Can anybody access data inside grub2, in later partitions in 3TB/4TB? Is any way to debug this? I will be happy if proved wrong.
Solved this by moving from bios mode to efi. Now I can boot from Debian on /dev/sda5 without any problem. Though it should have been bootable in bios mode as well. This is definitely bios limitation.
