Hello, I am trying to install Debian on a 4TB external HDD, and want to be able to boot it both on UEFI and BIOS systems. Using a simple BIOS/GPT configuration (GPT partitioning with BIOS boot) didn't work out - after receiving some important tips from this mailing list about problems that I had with this configuration I succeeded to boot on BIOS system, but not on UEFI system. Therefore I tried to combine BIOS+UEFI boots by creating both EFI and BIOS boot partitions, and then installing grub into both. Here is how the HDD was partitioned:
[root@arch]# parted /dev/sdb print Model: WD Elements 25A1 (scsi) Disk /dev/sdb: 4001GB Sector size (logical/physical): 512B/4096B Partition Table: gpt Disk Flags: Number Start End Size File system Name Flags 1 1049kB 2097kB 1049kB bios_grub 2 2097kB 202MB 200MB fat32 boot, esp 3 202MB 714MB 512MB ext4 4 714MB 8714MB 8000MB linux-swap(v1) 5 8714MB 4001GB 3992GB ext4 Partition 1 is intended for BIOS boot partition (for Stage 1.5 loader), partition 2 is the EFI partition, partition 3 is intended for the /boot (as was suggested previously on this mailing list) so that grub-related files will be located inside the 2TB limit and therefore be accessible to Stage 1.5 loader in BIOS mode, partition 4 is a swap, and 5 is the /. I performed Debian installation on a UEFI machine, and after an installation succeeded to boot the HDD. After that I installed grub into MBR: grub-install --target=i386-pc --recheck /dev/sdb Then I tried to boot on BIOS machine, and got the following error from grub: "error: attempt to read or write outside of disk 'hd0'" and was dropped into grub's rescue shell. I tried the following command: ls (hd0,gpt3)/ which listed the expected contents of the /boot partition. Then: set root=(hd0,gpt3) set prefix=(hd0,gpt3)/grub insmod normal and again I get the error message "error: attempt to read or write outside of disk 'hd0'" As far as I could find, usually this kind of an error happens when grub's files are located on a partition which is far from the beginning of a disk, but in my case this is not so. And since grub can list contents of a partition from a rescue shell, then it has access to the file system. Then what is the problem here?
