The below commands are the ones that I used in the above video

e2fsck -fy /dev/centos6/root

resize2fs -p /dev/centos6/root 15G

lvreduce -L 20G /dev/centos6/root

lvcreate -L 20G -n centos7 centos6

yum install lvm2 mdadm

dracut -f --add "ssh-client mdraid lvm" --add-drivers "raid1 dm-mod" -M initramfs-3.10.0-229.el7.x86_64.img 3.10.0-229.el7.x86_64

nano /boot/grub/grub.conf

root=UUID=5c0f7966-0500-4255-bb57-c29ded546a28