To this original question back to me: any EFI and XBOOTLDR partitions used in this way must exist on the same block device as the intended root and usr partitions. Dracut does a fantastic job of including any tools needed to boot most any setup, including RAID devices.
Most of my experience comes from making flash drives boot various computers with unknown hardware to run custom-made OS projects, so mileage will vary in a commercial environment. You should also be careful of relying on UEFI variables, as some (very!) flakey firmware versions can burn out from overuse. Feli Flitzberg Sent from Proton Mail for iOS. -------- Original Message -------- On Monday, 10/20/25 at 11:33 Demi Marie Obenour <[email protected]> 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? > Feli Flitzberg > > https://uapi-group.org/specifications/specs/discoverable_partitions_specification/ > > Sent from Proton Mail for iOS. > > -------- Original Message -------- > On Saturday, 10/18/25 at 19:50 Demi Marie Obenour <[email protected]> > wrote: > This isn't systemd-specific, but I know that at least some systemd > developers recommend using UEFI secure boot + dm-verity, which leads > to this problem. I also don't know a better place to ask for help > on this. > > How do OSs using dm-verity and UKIs find the user data partition? > On some systems it is trivial, as the storage device it must be on > is known ahead of time. However, desktops and servers can have many > storage devices or even use RAID, making this very nontrivial. > > Non-immutable OSs generally store this information in either the > initramfs, root filesystem, or kernel command line. However, with > signed UKIs and dm-verity both the initramfs and root filesystem are > provided by the OS vendor and can't be changed. This means that one > must load the user data partition to be able to read any data one > has stored on disk, but one must read data stored by the installer > to find the user data partition. Circular dependency, whoops. > > What is the standard solution to this problem, if any? The only one I > have come up with is UEFI variable storage, but I'm curious if there > are others. > -- > Sincerely, > Demi Marie Obenour (she/her/hers) > -- Sincerely, Demi Marie Obenour (she/her/hers)
