Added extra paragraph to document the 'rebuild' feature.

Reviewed by:	msmith

usr.sbin/mlxcontrol/mlxcontrol.8

@@ -72,7 +72,7 @@ Drive names are of the form "mlxdN"
 where N is the unit number of the drive.
 Do not specify the path to a device node.
 .Pp
-.Bl -tag -width status
+.Bl -tag -width rebuild
 .It status
 Print the status of controllers and system drives.
 If one or more drives are specified,
@@ -111,6 +111,21 @@ This command returns immediately;
 use the
 .Ar status
 command to monitor the progress of the check.
+.It rebuild
+Requires two arguments, 
+.Ar controller
+and
+.Ar physdrive
+as specified in the
+output of the
+.Ar status 
+command. All system drives using space on the physical drive
+.Ar physdrive 
+are rebuilt, reconstructing all data on the drive.
+Note that each controller can only perform one rebuild at a time.  This 
+command returns immediately; use the
+.Ar status
+command to monitor the progress of the rebuild.
 .It config
 Print the current configuration from the nominated controller.
 This command will be updated
@@ -119,6 +134,7 @@ in a future release.
 .It help
 Print usage information for
 .Ar command .
+.El
 .Sh BUGS
 The
 .Ar config