On 10/20/25 16:21, Lennart Poettering wrote: > On Mo, 20.10.25 14:02, Demi Marie Obenour ([email protected]) wrote: > >> On 10/20/25 13:57, Andrei Borzenkov wrote: >>> 20.10.2025 20:33, Demi Marie Obenour wrote: >>>> On 10/19/25 11:36, Feli Flitzberg wrote: >>>>> Hi, long time watcher, first time poster. If the bootloader supports the >>>>> Discoverable Partitions Specification, all that's needed is the correct >>>>> partition GUID assigned to every partition. After that, you don't need to >>>>> pass any partitions or use /etc/fstab as the bootloader will read the >>>>> disk it came from to mount everything. The only major limitation is that >>>>> your bootloader partition MUST live on the same disk as root and usr, >>>>> otherwise they won't be found. Hope this helps! >>>> >>>> How can the OS know which block device the system was booted from? >>>> >>> >>> >>> Bootloader compliant with BLI sets the LoaderDevicePartUUID EFI >>> variable. Otherwise I assume it possible to get the current boot entry >>> number from the BootCurrent EFI variable and parse the corresponding >>> BootXXXX entry. >> >> Is this EFI variable the partition table UUID (which identifies a device) >> or a partition UUID (which does not)? > > LoaderDevicePartUUID reports the partition UUID of the ESP > systemd-boot or systemd-stub first were invoked from. > > StubDevicePartUUID reports the partition UUID of the partition the UKI > was invoked from (which is typically also the ESP, but could also be > XBOOTLDR or in fact any oher partition). > > But note that the ESP/XBOOTLDR partition UUIDs should generally be > understood to be as useful for identifying specific drives as the > GPT partition table UUID, as the ESPs/XBOOTLDR have to be generated > individually for each drive, as they are writable and recognzable by > firmware, as they are referenced by firmware via their partition UUID > too.
Can some sort of ACPI path be used? The firmware uses fairly long paths internally. -- Sincerely, Demi Marie Obenour (she/her/hers)
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