Simple initramfs with luks support


        mkdir /usr/src/initramfs 
		 # Basic directories structure
		mkdir --parents /usr/src/initramfs/{bin,dev,etc,lib,mnt/root,proc,root,sbin,sys,usr/lib} 
		 # Minimal stuff needed
		cp --archive /dev/{console,null,random,tty,urandom,sda,sda1,sda2,sda3} /usr/src/initramfs/dev/
		cp --parents /proc/sys/kernel/printk /usr/src/initramfs/
		cp --parents /etc/fstab /usr/src/initramfs/

Binary / library

bin/busybox, sbin/cryptsetup, sbin/switch_root and sbin/init

For binary build dynamically, copy library and simlink into their respective path

Bash script init

A init as simple of init will work

Place the init file at the root of the initramfs directory and apply a chmod +x

Generate the initramfs

A the root directory of the initramfs directory, execute


		   find . -print0 | cpio --null --create --verbose --format=newc > /boot/initrd-{KERNELVERS}.cpio

Extra

To automatically keep your binary/library up to date, you can use libbin placed at the root directory of your initramfs.

Grub entry

A simple as


		  menuentry 'Gentoo' {
		   insmod part_msdos
		   insmod crypto
		 insmod cryptodisk
		 insmod luks
		 insmod cpio
         set root='hd0,msdos1'
linux /vmlinuz-4.19.152 luks enc_root=UUID={UUID_CRYPTO_LUKS} root=UUID={UUID_ROOT}
initrd /initrd-4.19.152.cpio
}