I am using Debian Scratch with encrypted root partition. The last kernel version where it worked was 4.6.0. For kernels 4.7.0 and 4.8.0 it prints on the boot repeatedly and forever following messages:  WARNING: Failed to connect to lvmetad. Falling back to device scanning.  Volume group martin-vg not found  Cannot process volume group martin-vgIn 4.6.0 these messages are shown too, but only twice and then it prompts for a password:Please unlock disk sda5_crypt:How to fix it?
Debian fails to prompt for encrypted disk password on boot
debian;boot;dm crypt;disk encryption