Grant Edwards wrote: > On 2023-10-18, Michael <confabul...@kintzios.com> wrote: >>> The protective MBR and the BIOS boot partition are two different, >>> unrelated things. The BIOS boot partition is a real partition (usually >>> 1-2MB in size) that's present in the GPT parition table. It's used by >>> Grub as a place to store its files. >> Yes, this is needed on GPT disks when installed on BIOS MoBos. > There is a way to install Grub on GPT disks without it, but it takes > extra work and isn't worth it. You have to lock certain files in place > under /boot/grub so that block-lists can be embedded in sector 0. > > All of the disk label utilities I've seen recently will, by default, > leave a sizable empty space between the primary GPT table and the > start of the first partition (which typically starts at a 1MB offset > from the start of the disk). I've never understood why Grub won't use > that space they way it will use the empty space between an MBR and the > first partition. > >>> It must be the first partition, and it doesn't have a real >>> filesystem (grub uses some sort of private filesystem): >> I'm not sure it uses any filesystem. I understood it uses a raw sector jump >> from the MBR to the GPT partition type 0xEE. > I've read a couple vague but differing descriptions of it. One > description specifically referred to "files" (plural) and some sort of > grub-private-internal filesystem. However, it could be that it's > nothing but a single "file" starting at block 0 in that partition. > Whatever it is, it seems to be "opaque" in that Grub puts stuff in > that partition, Grub later uses that stuff, and nobody else needs to > know or care what it is or how it's organized. I haven't looked > through the Grub source code to try to see inside the black box... > > -- > Grant >
I used cgdisk and GPT for my disk even tho it is small, only 300GBs or so, mostly out of habit. The grub install failed and I did a search. I found this and it worked. grub-install fails with "grub-install: warning: this GPT partition label contains no BIOS Boot Partition; embedding won't be possible." Using parted command. # parted /dev/sda # set 1 boot off # set 1 bios_grub on # q # then install grub. This happens on drives where GPT is used instead of MBR. This may be something you want to make note of. I guess it changes the way grub sees it or something. Anyway, it worked fine after that so may be worth making a note of in case one of you ever needs it. Dale :-) :-) P. S. My off topic Ubuntu thread is covering a lot of strange things. LOL
