In the rare situation where you have multiple partitions
defined for one disk and have the 10th partition mounted,
(eg, /dev/sda10), and want to build a raid partition on
the 1st partition (eg, /dev/sda1) "mkraid" will claim that
the partition is mounted (eg "/dev/sda1 mounted!").  This
is due to an incorrect pattern match while reading
/etc/mtab.  ('/dev/sda1' matches '/dev/sda10' incorrectly.)

This can be worked around by temporarily editing out the
10th partition entry in /etc/mtab while mkraid is running
its initial verifications.

Once the raid is actually created, everything is fine.