Create raid1

mdadm --create --verbose --level=raid1 /dev/md0 --raid-devices=2 /dev/sda6 /dev/sdb1

# Do not run sync
mdadm --create --verbose --level=raid1 /dev/md0 --raid-devices=2 --assume-clean /dev/sda6 /dev/sdb1

Create raid5

mdadm --create --verbose --level=raid5 /dev/md0 --raid-devices=3 /dev/sda1 /dev/sdb1 /dev/sdc1

After unclean shutdown

/sbin/mdadm /dev/md0 --fail /dev/sda5 --remove /dev/sda5
/sbin/mdadm /dev/md0 --add /dev/sda5

Stop md device

mdadm --manage --stop /dev/md0