Re: boot.cfg dev command not working

[Michael van Elst <mlelstv%serpens.de@localhost>]

On Sun, Mar 23, 2025 at 06:46:19PM +0700, Robert Elz wrote:
>   | UEFI doesn't even know the "bootme" attribue, so that must be something
>   | else.
> 
> It is even worse than that, despite what our gpt(8) might allow one to
> believe, it is impossible to set "bootme" on an ESP.   "bootme" is one
> of the flag bits in the upper 16 bits of the GPT partition flags word,
> and those have a meaning defined by the partition type, they're not global.

True. On the other hand, people don't use them depending on the
"partition type" but more depending on "the OS running".


>   | N.B. it might know the "biosboot" attribute.
> 
> It might, that is a globally defined bit (though why it exists that way
> perplexes me) - it applies to all partition types.   What firmware might do
> with it if set on an ESP is anyone's guess I think.

It's supposed to be the same as the "active partition" flag in an MBR,
so if you have multiple ESPs, it could signal a preference to the
firmware. But since there are already mechanisms to handle multiple
ESPs, it probably signals the bootloader what to look at. Which then
means, it's like a generic "BOOTME" flag, except that we can't be sure :)