I have the following setup: A LUKS encrypted SSD on which a LVM is used to form the typical linux partitions (/, /home/, etc.). This setup is unlocked at boot by a password. I'm using Debian Jessie.
Due to the lack of space, I wanted to add another PV to the LVM, which of course should be LUKS encrypted and decrypted at boot - with the use of key derivation from the first PV or by using the same password as the first PV.
This means that the LVM (which includes /, /home/, etc.) spans over two LUKS encrypted SSDs (of course each SSD contains one partition that is actually encrypted and not the SSDs themselves, but I think this is obvious.).
It seems impossible to unlock this kind of setup at boot since Systemd has been integrated - all found instructions derive keys (or else) that is not possible to do anymore with Systemd beacause the key derivation scripts are not executed anymore at boot (or the instructions just fail).
Does someone know if and how this actually works?
Otherwise I have to change my setup to have a seperate root partition (outside the LVM) so that the rest can be mounted after boot, or to have luks inside the lvm. But both are the last options I want to choose.