Dear Maintainer, When installing mdadm (apt install mdadm) in presence of 2 already existing RAID arrays, the creation of /etc/mdadm/mdadm.conf goes wrong. Under the "# definitions of existing MD arrays" line, there are 2 lines for the 2 different arrays, but both are assigned to /dev/md/0 - and because of that, only the first array is automatically assembled at startup (the second one have to be assembled manually). # definitions of existing MD arrays ARRAY /dev/md/0 metadata=1.2 UUID=43c0447b:9c411b87:800d69f9:86dfe0d3 name=Pix-Server-Boutigny:0 ARRAY /dev/md/0 metadata=1.2 UUID=4042f02a:f1d2c565:91a6dacf:bb3ca761 name=VALEFORT:0 Changing to /dev/md0 and /dev/md1 for example, was able to solve the issue caused by this bug (after update-initramfs -u and reboot, both arrays are now assembled automatically). I have been able to check that I have the same issue on a second computer, in my example, having a 3 disks RAID 5 array, and another 3 disks RAID 0 array. But others kinds of RAID arrays are probably affected too. Hope this report will help, and also hope this bug will be easy to solve! Best regards, Julien ROBIN