Rebuilding the initramfs in RHEL 6

It is recommended you make a backup copy of the initrd in case the new version has an unexpected problem

Now rebuild the initramfs for the current kernel version:

# dracut -f

If you are in a kernel version different to the initrd you are building you must specify the full kernel version, including architecture

For example 

# dracut -f /boot/initramfs-2.6.32-220.7.1.el6.x86_64.img 2.6.32-220.7.1.el6.x86_64