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NEWFS(8)		  BSD System Manager's Manual		      NEWFS(8)

NAME
     newfs, mount_mfs — construct a new file system

SYNOPSIS
     newfs [-NO] [-S sector-size] [-T disktype] [-a maxcontig] [-b block-size]
	   [-c cylinders] [-d rotdelay] [-e maxbpg] [-f frag-size] [-i bytes]
	   [-k skew] [-l interleave] [-m free space] [-n rotational positions]
	   [-o optimization] [-p sectors] [-r revolutions] [-s size]
	   [-t tracks] [-u sectors] [-x sectors] special
     mount_mfs [-N] [-T disktype] [-a maxcontig] [-b block-size]
	   [-c cylinders] [-d rotdelay] [-e maxbpg] [-f frag-size] [-i bytes]
	   [-m free space] [-n rotational positions] [-o options] [-s size]
	   special node

DESCRIPTION
     Newfs replaces the more obtuse mkfs(8) program.  Before running newfs or
     mount_mfs, the disk must be labeled using disklabel(8).  Newfs builds a
     file system on the specified special device basing its defaults on the
     information in the disk label.  Typically the defaults are reasonable,
     however newfs has numerous options to allow the defaults to be selec‐
     tively overridden.

     Mount_mfs is used to build a file system in virtual memory and then mount
     it on a specified node.  Mount_mfs exits and the contents of the file
     system are lost when the file system is unmounted.	 If mount_mfs is sent
     a signal while running, for example during system shutdown, it will
     attempt to unmount its corresponding file system.	The parameters to
     mount_mfs are the same as those to newfs.	If the -T flag is specified
     (see below), the special file is unused.  Otherwise, it is only used to
     read the disk label which provides a set of configuration parameters for
     the memory based file system.  The special file is typically that of the
     primary swap area, since that is where the file system will be backed up
     when free memory gets low and the memory supporting the file system has
     to be paged.

     The following options define the general layout policies.

     -N		 Causes the file system parameters to be printed out without
		 really creating the file system.

     -O		 Creates a 4.3BSD format filesystem.  This options is primar‐
		 ily used to build root filesystems that can be understood by
		 older boot ROMs.

     -T		 Uses information for the specified disk from /etc/disktab
		 instead of trying to get the information from a disklabel.

     -a maxcontig
		 This specifies the maximum number of contiguous blocks that
		 will be laid out before forcing a rotational delay (see the
		 -d option).  The default value is one.	 See tunefs(8) for
		 more details on how to set this option.

     -b block-size
		 The block size of the file system, in bytes.

     -c #cylinders/group
		 The number of cylinders per cylinder group in a file system.
		 The default value is 16.

     -d rotdelay
		 This specifies the expected time (in milliseconds) to service
		 a transfer completion interrupt and initiate a new transfer
		 on the same disk.  The default is 4 milliseconds.  See
		 tunefs(8) for more details on how to set this option.

     -e maxbpg	 This indicates the maximum number of blocks any single file
		 can allocate out of a cylinder group before it is forced to
		 begin allocating blocks from another cylinder group.  The
		 default is about one quarter of the total blocks in a cylin‐
		 der group.  See tunefs(8) for more details on how to set this
		 option.

     -f frag-size
		 The fragment size of the file system in bytes.

     -i number of bytes per inode
		 This specifies the density of inodes in the file system.  The
		 default is to create an inode for each 2048 bytes of data
		 space.	 If fewer inodes are desired, a larger number should
		 be used; to create more inodes a smaller number should be
		 given.

     -m free space %
		 The percentage of space reserved from normal users; the mini‐
		 mum free space threshold.  The default value used is 10%.
		 See tunefs(8) for more details on how to set this option.

     -n rotational positions
		 Determines how many rotational time slots there are in one
		 revolution of the disk.

     -o optimization preference
		 (``space'' or ``time'') The file system can either be
		 instructed to try to minimize the time spent allocating
		 blocks, or to try to minimize the space fragmentation on the
		 disk.	If the value of minfree (see above) is less than 10%,
		 the default is to optimize for space; if the value of minfree
		 is greater than or equal to 10%, the default is to optimize
		 for time.  See tunefs(8) for more details on how to set this
		 option.

     -s size	 The size of the file system in sectors.

     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 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 impos‐
     sible for fsck to find the alternate superblocks if the standard
     superblock is lost.

     -S sector-size
		 The size of a sector in bytes (almost never anything but
		 512).

     -k sector 0 skew, per track
		 Used to describe perturbations in the media format to compen‐
		 sate for a slow controller.  Track skew is the offset of sec‐
		 tor 0 on track N relative to sector 0 on track N-1 on the
		 same cylinder.

     -l hardware sector interleave
		 Used to describe perturbations in the media format to compen‐
		 sate for a slow controller.  Interleave is physical sector
		 interleave on each track, specified as the denominator of the
		 ratio:
		       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.

     -p 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 (-u) since they are not
		 available to the file system for data allocation.

     -r revolutions/minute
		 The speed of the disk in revolutions per minute.

     -t #tracks/cylinder
		 The number of tracks/cylinder available for data allocation
		 by the file system.

     -u 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 the
		 -p option.)

     -x spare sectors per cylinder
		 Spare sectors (bad sector replacements) are physical sectors
		 that occupy space at the end of the last track in the cylin‐
		 der.  They are deducted from the sectors/track (-u) of the
		 last track of each cylinder since they are not available to
		 the file system for data allocation.

     The options to the mount_mfs command are as described for the newfs com‐
     mand, except for the -o option.

     That option is as follows:

     -o	     Options are specified with a -o flag followed by a comma sepa‐
	     rated string of options.  See the mount(8) man page for possible
	     options and their meanings.

SEE ALSO
     disktab(5), fs(5), dumpfs(8), disklabel(8), diskpart(8), fsck(8),
     format(8), mount(8), tunefs(8)

     M. McKusick, W. Joy, S. Leffler, and R. Fabry, "A Fast File System for
     UNIX,", ACM Transactions on Computer Systems 2, 3, pp 181-197, August
     1984, (reprinted in the BSD System Manager's Manual).

HISTORY
     The newfs command appeared in 4.2BSD.

4.2 Berkeley Distribution	  May 3, 1995	     4.2 Berkeley Distribution
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