cat /proc/mdstat
mdadm -E /dev/sda2
mdadm --detail --scan
mdadm --detail /dev/md0
mdadm --add /dev/md0 /dev/sda2
To switch a raid array from read-only mode:
mdadm --readwrite /dev/md0
Some geek stuff, some not so geek stuff.
cat /proc/mdstat
mdadm -E /dev/sda2
mdadm --detail --scan
mdadm --detail /dev/md0
mdadm --add /dev/md0 /dev/sda2
To switch a raid array from read-only mode:
mdadm --readwrite /dev/md0