I'm trying to install NixOS 19.09 on a notebook. My disk setup is a 30GB SSD and a 700GB HDD. I decided that I want to use the SSD as cache for the HDD, and also that I want the entire root partition to be encrypted.
My partition setup therefore looks like this:
- /dev/sda - SSD
- /dev/sda1 - boot partition, UEFI bootable flag, formatted with FAT, unencrypted
- /dev/sda2 - to be used for the cache
- /dev/sdb - HDD, unpartitioned, to be used as the main disk with LVM
I formatted /dev/sda1 with mkfs.fat, I set up a volume group vg that included /dev/sda2 and /dev/sdb, and I then followed the guide that you can find in the lvmcache manual page. After creating a single cached volume called hdd0, I ran cryptsetup on it, so that I could achieve a LUKS-on-LVM scheme. The entire cached hdd0 is encrypted with LUKS2.
Then I unlocked hdd0 again using cryptsetup, mapping it to /dev/mapper/root. I mounted /mnt on it, created /mnt/boot and mounted /dev/sda1 there. After that, I generated a NixOS config and basically left it at default, with the notable changes of adding dm-cache to boot.initrd.kernelModules, and setting boot.initrd.luks.devices."root".preLVM to false. Then, I ran
nixos-install successfully and rebooted.
The system managed to successfully run GRUB, but after that failed to find the root volume. It provided an error message of:
device-mapper: table: 254:3: cache: Error creating cache's policy device-mapper: reload ioctl on (254:3) failed: Invalid argument
I'm assuming it has a problem with detecting the entire hdd0. I tried booting it from the live installation USB stick, and there you have to enable dm-cache using modprobe and then run
# lvchange -ay vg
to get hdd0 to be active and visible.
Did anyone try a similar setup? How can I get it to boot automatically? Or is the setup flawed conceptually and can never work?
PS: I hope the question is detailed enough, it's my first time asking here.