[ubuntu] restoring grub2 record on each drive of a raid 5 or 6 array

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http://ubuntuforums.org – After expanding a raid 6 mdadm array from 4 to 5 drives, with --add and --grow, and before any updates to grub were made, computer was restarted. At boot, it now says something about an invalid arch independent ELF magic, and a grub rescue> prompt. Since the raid hosts /, I wonder if the ability of grub to assemble the md0 to get to /boot is now compromised. I have no idea how does that part work... What I have done, I booted from the "live usb" and have also found that as a part of my previous attempts to boot from the raid, one drive fell out (sdc), and --assemble --s (Hardware)