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After fixing the missing md devices as above, the VGs and LVs can be enabled by running the busybox command lvm and then using its help to find the commands to do so (cut down versions of the GNU Linux equivalents).
Messages
auto-read-only
Seen in /proc/mdstat. Normal until after the first write to the device (can be forced).
/etc/mdadm/mdadm.conf defines no arrays
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