If you make a change to a configuration file that needs to be reflected in your Linux boot process (such as mdadm.conf), you’ll need to add it to your initramfs image.
This process varies by distribution (although most that I have used share the method I describe for Debian).
To update initramfs for Debian, run the command:
In Fedora, run the command
dracut -f /boot/initramfs-currentimage
initramfs-currentimage is replaced with the name of the image you are currently using.
Both commands can be used with different switches to create new images as well, but since that involves updating grub as well, I’ll leave it for a later time.