Updating grub to grub-

I think I have a BIOS-MBR and not UEFI because if I issue the command “ls /sys/firmware/efi”, I get ‘no such file or directory’.

I’m looking at the instructions for updating grub for BIOS-MBR and the first instruction is to “sudo grub-install /dev/sdy”. I know I need to replace “sdy” with my particular installation. I’m just not sure if I shoud use ‘sda’ or ‘sda1’.

Here is the info I get from “fdisk -l”:

fdisk -l
Disk /dev/sda: 698.65 GiB, 750156374016 bytes, 1465149168 sectors
Disk model: TOSHIBA MK7575GS
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x5886c2ab

Device Boot Start End Sectors Size Id Type
/dev/sda1 * 2048 409599 407552 199M 7 HPFS/NTFS/exFAT
/dev/sda2 409600 1250015231 1249605632 595.9G 5 Extended
/dev/sda3 1456826368 1465145343 8318976 4G c W95 FAT32 (LBA)
/dev/sda5 411648 1249980415 1249568768 595.9G 83 Linux
/dev/sda6 1249982464 1250015231 32768 16M 82 Linux swap / Solaris

So, do I replace “sdy” with ‘sda’ or ‘sda1’?


In short:

sudo grub-install /dev/sda installs the MBR on the first sectors of the harddrive. So please don’t use partitions, but the whole drive (no numbers).

sudo update-grub updates the “bootmenu”.

Here is more information about it: GRUB - ArchWiki

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Excellent. I’d been wondering about that as I have been making my installations on GPT disks for a few years now but all but one are currently in Legacy mode. The information I needed is right there! Thanks to those who produce the Arch Wikis.

BTW I can’t actually remember how I did this as it’s been quite a while, but I can confirm the installer had no issues with the way i’d set up the partitions, think I used the “created for future use, but not currently required for UEFI” EFI partition to install GRUB. It’s fat32 but only has the “boot” flag and not the “bios_grub” flag set.

Any hints on how to confirm where GRUB installed its gubbins will be appreciated!

I might start a thread on whether it’s worth converting my current installation to UEFI as the disk is already prepared for such …