I am also affected by this regression. It looks like Wheezy disables udev for md and uses an rc-script for assembling at boot; therefore it will not automatically assemble arrays after boot. Trusty assembles real devices during and after boot, but seems to ignore virtual devices like /dev/md0.
So I added a new rule for virtual devices to the existing udev rules in Trusty. I created /etc/udev/rules.d/85-mdadm.rules with this single line rule: SUBSYSTEM=="block", ACTION=="add|change", ENV{ID_FS_TYPE}=="linux_raid_member", DEVPATH=="*/virtual/*", RUN+="/sbin/mdadm --incremental $tempnode" This rule (plus the existing ones) assemble my nested raid during boot or any time later, but might not work for the root filesystem unless a initramfs-tools/hooks script is created (not tested). -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1171945 Title: Nested RAID levels aren't started after reboot To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/mdadm/+bug/1171945/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs