"Failed to start Apply Kernel Variable" after converting the root filesystem from XFS to EXT4

[Nicolas C.]

Hello,

A had a RHEL7 VMware template with the root filesystem in XFS. I tried 
to copy the system to an EXT4 partition but now I have the message 
during boot : "Failed to start Apply Kernel Variable"

http://i.imgur.com/atEjCuO.png

This is how I've proceeded :

  - boot on LiveCD

  - copy from the XFS partition to EXT4

  - chroot

  - initramfs rebuild with "dracut"

  - re-generation of "grub.cfg" with "grub2-mkconfig"

  - /etc/fstab update to change the filesystem of "/" from "xfs" to "ext4"

A few things :

  - /boot partition is ext4 on its own 1G drive

  - / partition is a LVM Logical Volume, the Physical Volume is a 
dedicated drive of 16G

Anyone know how I can get further? I can boot the system in single mode 
or LiveCD... I try to remove all kernel options in the Grub menu, no 
success...

Thanks,

Nicolas