-.SH FILES
-/etc/disktab for disk geometry and file system partition information
-.br
-/etc/mkfs to actually build the file system
-.br
-/usr/mdec for boot strapping programs
-.SH "SEE ALSO"
-disktab(5),
-fs(5),
-diskpart(8),
-fsck(8),
-format(8),
-mkfs(8),
-tunefs(8)
-.PP
-M. McKusick, W. Joy, S. Leffler, R. Fabry,
-``A Fast File System for UNIX'',
-\fIACM Transactions on Computer Systems 2\fP, 3.
-pp 181-197, August 1984.
-(reprinted in the System Manager's Manual, SMM:14)
-.SH BUGS
-Should figure out the type of the disk without the user's help.
+.It Fl c Ar #cylinders/group
+The number of cylinders per cylinder group in a file system.
+The default value used is 16.
+.It Fl s Ar size
+The size of the file system in sectors.
+.Pp
+The following options override the standard sizes for the disk geometry.
+Their default values are taken from the disk label.
+Changing these defaults is useful only when using
+.Nm newfs
+to build a file system whose raw image will eventually be used
+on a different type of disk than the one on which it is initially
+created (for example on a write-once disk).
+Note that changing any of these values from their
+defaults will make it impossible for
+.Xr fsck
+to find the alternate superblocks if the standard super block is lost.
+.It Fl r Ar revolutions/minute
+The speed of the disk in revolutions per minute.
+.It Fl S Ar sector-size
+The size of a sector in bytes (almost never anything but 512).
+.It Fl u Ar sectors/track
+The number of sectors per track available for data
+allocation by the file system. This does not
+include sectors reserved at the end of each track
+for bad block replacement (see
+.Fl p
+below).
+.It Fl t Ar #tracks/cylinder
+The number of tracks/cylinder available for data
+allocation by the file system.
+.It Fl p Ar spare sectors per track
+Spare sectors (bad sector replacements) are physical sectors
+that occupy space at the end of each track.
+They are not counted as part of the sectors/track
+.Pq Fl u
+since they are not available to the file system for data allocation.
+.It Fl x Ar spare sectors per cylinder
+Spare sectors (bad sector replacements) are physical sectors
+that occupy space at the end of the last track in the cylinder.
+They are deducted from the sectors/track
+.Pq Fl u
+of the last track of each cylinder
+since they are not available to the file system for data allocation.
+.It Fl l Ar hardware sector interleave
+Used to describe perturbations in the media format to
+compensate for a slow controller.
+Interleave is physical sector interleave on each track,
+specified as the denominator of the ratio:
+.Dl sectors read/sectors passed over
+Thus an interleave of 1/1 implies contiguous layout, while 1/2
+implies logical sector 0 is separated by one sector from logical
+sector 1.
+.It Fl k Ar sector \&0 skew , per track
+Used to describe perturbations in the media format to
+compensate for a slow controller.
+Track skew is the offset of sector 0 on track N
+relative to sector 0 on track N-1 on the same cylinder.
+.Pp
+.El
+The following option applies only to
+.Nm mfs .
+.Bl -tag -width Fl
+.It Fl F Ar mount flags
+Used to pass in a decimal numeric value to be passed
+as mount flags when running as a memory based file system.
+This option is primarily intended for use when
+.Nm mfs
+is started by the
+.Xr mount 8
+command.
+.El
+.Sh SEE ALSO
+.Xr disktab 5 ,
+.Xr fs 5 ,
+.Xr disklabel 8 ,
+.Xr diskpart 8 ,
+.Xr fsck 8 ,
+.Xr format 8 ,
+.Xr tunefs 8
+.Rs
+.%A M. McKusick
+.%A W. Joy
+.%A S. Leffler
+.%A R. Fabry
+.%T A Fast File System for UNIX ,
+.%J ACM Transactions on Computer Systems 2
+.%V 3
+.%P pp 181-197
+.%D August 1984
+.%O (reprinted in the BSD System Manager's Manual)
+.Re
+.Sh HISTORY
+The
+.Nm
+command appeared in
+.Bx 4.2 .