System: Gentoo linux with Grub2.
I got new ssd drive, so I want to move root partition to this device. At moment I have these partitions:
/dev/sda1 2048 6143 4096 2M BIOS boot
/dev/sda2 6144 268287 262144 128M EFI System
/dev/sda3 268288 8388607 8120320 3.9G Linux filesystem
/dev/sda4 8388608 134217727 125829120 60G Linux filesystem
/dev/sda5 134217728 974676015 840458288 400.8G Linux filesystem
where sda2 is boot partition, sda3 - swap, sda4 - root, sda5 is lvm device.
New drive is fully managed by lvm. New root partition located at /dev/samsung-ssd/root. I've already changed /etc/fstab on new root.
I've read this answer https://unix.stackexchange.com/a/5318, but it suggests to move boot partition with root to new device, where I want to keep boot on old disk.
I tried to edit grub.conf and replace kernel boot option from root=/dev/sda4 to root=/dev/samsung-ssd/root, but got a kernel panic (failed to find root partition).
So my question is how to move root partition to new drive and keep boot partition on old?