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how to fix mdadm.conf defines no arrays on UBUNTU SERVER 16.04
While performing reports on Ubuntu server 16.04 we see the accompanying cautioning. (Tolerating it is a notice, it is none-the-less irritating).
Setting up initramfs-tools (0.122ubuntu8.3) ...
update-initramfs: deferring update (trigger activated)
Processing triggers for initramfs-tools (0.122ubuntu8.3) ...
update-initramfs: Generating /boot/initrd.img-4.4.0-38-generic
W: mdadm: /etc/mdadm/mdadm.conf defines no arrays.
The notice is shown at whatever point there's no Exhibit line in mdadm.conf

The least complex fix for this notice is to add the accompanying line to the finish of/and so on/mdadm/mdadm.conf 
ARRAY <ignore> devices=/dev/sda