ideally should boot rootfs from a matching hard drive

[Dimitri John Ledkov]

Ideally we should strive to boot rootfs from a matching hard drive.

I.e. if we are booting rootfs by UUID, we should try to find the one that came from the same drive as where ESP (UEFI) came from, or u-boot spl / u-boot got loaded from (loader1/loader2).

Such that for example, when booted from external usb stick, rootfs from there is mounted.

Or when booted from internal drive whilst a dd backup is attached over usb, rootfs is loaded from the internal drive not from the usb attached backup.

This would need:

* u-boot to export the drive it loaded extlinux.conf / bootscript from, and pass it on kernel command line

* grub to export the device UUID it got loaded from (from the BootServices EFI table) and pass it on the kernel command line or via runtime EFI variable

* sdboot already does that I believe, but not sure if initramfs-tools consumes the sdboot provided information

* initramfs-tools to consume above and sort the discovered devices based on that, when deciding what to mount as rootfs

[Julian Andres Klode (juliank)]

This proposal seems somewhat incompatible with our resilient boot specification.

[Dimitri John Ledkov (xnox)]

My understanding of resilient boot is that there are multiple ESPs trying to boot the same raid device.

If there is only one rootfs filesystem, boot that one. Which in case of raid, there will be only one.

I'm more concerned about the case of two ubuntu-server preinstalled images on two usb sticks not booting of the right place, when there are two different installations.

[Julian Andres Klode (juliank)]

Just to not forget: This should work. We pass the ESP/boot partition to kernel, initramfs then looks at it, and if it finds UUID on same drive, it will take that one. If not it will take UUID from any drive, thus handling RAID or encryption automagically.

[Dan Streetman (ddstreet)]

does this need to target systemd? It doesn't sound like any change is needed to systemd for this right?

[Julian Andres Klode (juliank)]

that's for systemd-boot, but oh well, nothing uses that in Ubuntu

[Dan Streetman (ddstreet)]

unfortunately yeah, so...don't really need to target this to systemd then right

[Heinrich Schuchardt (xypron)]

Passing the ESP device
----------------------

All UEFI firmware already passes the device path of the loaded image in the EFI_LOADED_IMAGE_PROTOCOL installed on the handle passed to the loaded binary (shim, GRUB, Linux, ...). So your requirement is already fulfilled.

We just have to stop using legacy booting mechanisms.

UUIDs
-----

UUIDs are globally unique IDs. If two partitions with the same UUID exist in the system ,this is a grave user error. We should not try to fix it.

Which remaining gap do you see? Or can we close this bug report as invalid?

Best regards

Heinrich

[Julian Andres Klode (juliank)]

My understanding is that this has not been addressed yet. We need to actually make use of that data even if UEFI gives us that.