Scan and assemble: # mdadm --assemble --scan Scan to update mdadm.conf # mdadm -Es >> /etc/mdadm/mdadm.conf   If not md device has been found, or you have only one disk from two of the RAID1, you can force to re-create the md device. The important parameter is "missing", that will make mdadm to create the mirror with only one member:   # mdadm --create /dev/md127 --assume-clean --level=mirror --verbose --raid-devices=2 /dev/sda missing mdadm: /dev/sda appears to be part Read more...