Automatically boot when a RAID is degraded

By default, Ubuntu and some other versions of Linux will stop the boot process and prompt you to take action if a degraded RAID is found. On an interactive system, this is fine but on a system that is often unattended this is a problem because it will prevent booting.

To prevent this from happening, you need to modify one line of the mdadm config file.

#> sudo vi /etc/initramfs-tools/conf.d/mdadm

Make sure the value for BOOT_DEGRADED is set to true.

BOOT_DEGRADED=true

Once this is done, the system will continue booting even when a degraded RAID is detected. It is up to you to monitor your drives and their health. But with this setting in place, your computer won't be dead in the water during the boot process.