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Mdadm Helpers
How do I replace a disk marked as removed from a linux md raid-5 array
First identify removed drive:
lsblk
the, if drive is just remved:
mdadm --zero-superblock /dev/sdXn mdadm /dev/md0 --add /dev/sdXn
If replacing damaged drive, then only:
mdadm /dev/md0 --add /dev/sdXn