multipath-tools-boot is not installed when the boot device is not a multipath device while the root files system is on a mutipath device

[Mr. Bob]

I installed Ubuntu 22.04 onto a Dell VRTX system. Due to some limitations of the system, I have to install the /boot and /boot/efi filesystem onto a non-multipath device, while the root file system (/) is installed on the multipath drive.
However, the installer will not install the package multipath-tools-boot during the process. As a result, the system will not be able to boot successfully after the installation is completed and dropped into the (initramfs) prompt.
It seems that there is some bug for the installer to decide if the multipath-tools-boot package needs to be installed or not when the boot file systems are not on a multipath drive.

For detailed information, please see my blogs:
https://mrbob0473.blogspot.com/2022/07/problem-installing-ubuntu-2204-lts-on.html
https://mrbob0473.blogspot.com/2022/07/ubuntu-2204-multipath-io-problem-with.html
https://mrbob0473.blogspot.com/2022/07/reproducing-multpath-io-issue-with.html
https://mrbob0473.blogspot.com/2022/07/fixing-ubuntu-2204-boot-iussing-on-dell.html

[Michael Hudson-Doyle (mwhudson)]

Hmm it certainly looks like curtin should install multipath-tools-boot in this situation. Do you have a log file from one of these installs?

[Mr. Bob (mrbob0473)]

I was able to reproduce the issue again this afternoon. Please find the log file from the attached ZIP file.

[Michael Hudson-Doyle (mwhudson)]

Argh, I think the issue here is that / is set up to be an LV of a LVM VG who's PV is a multipath disk? The code to detect multipath doesn't seem to handle this case :(

[Mr. Bob (mrbob0473)]

That's correct. The PVs are presented to the system with multiple access path. The VG is created on top of the multipath PV. But if there is no other non-multipath PV in the system, it will not hit the issue.