Boot.initrd.luks dependent devices

I have a USB key (encrypted by password) to unlock my root partition with luks. In configuration, I unlock the USB key in boot.intrd.luks as /dev/mapper/usb and then use it as key file for another luks device: boot.initrd.systemd.enable = true; boot.initrd.luks.devices = { usb.device = "/dev/disk/by-uuid/..."; # root partition root = { device = "/dev/disk/by-uuid/..."; keyFile = "/dev/mapper/usb"; crypttabExtraOpts = [ "plain" "keyfile-offset=..." ]; } } It works for a wh...