Imagine you’re repartitioning a disk and when you quit fdisk writing the new partition table automount tries to mount new partitions. So instead of refreshed disk ready for newfs you get this warning:
WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table.
The new table will be used at the next boot.
So you can forget about newfs for awhile. What do you do? Just reboot? What if you need to repartition more then one disk? Here is the solution …