Gentoo handbook https://wiki.gentoo.org/wiki/Handbook:AMD64

LUKS https://wiki.gentoo.org/wiki/Full_Disk_Encryption_From_Scratch

Gentoo + LVM + LUKS https://amedeos.github.io/gentoo/2019/01/14/install-gentoo-with-luks-lvm-and-systemd.html

DRACUT https://wiki.gentoo.org/wiki/Rootfs_encryption#Dracut

LVM https://wiki.gentoo.org/wiki/LVM

linux-4.9 Enabling LVM

Device Drivers  --->
   Multiple devices driver support (RAID and LVM)  --->
       <*> Device mapper support
           <*> Crypt target support
           <*> Snapshot target
           <*> Mirror target
           <*> Multipath target
               <*> I/O Path Selector based on the number of in-flight I/Os
               <*> I/O Path Selector based on the service time

install lvm

emerge --ask sys-fs/lvm2

LUKS

emerge --ask sys-fs/cryptsetup