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 :)
