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

NAME
     newfs, mount_mfs -- construct a new file system

SYNOPSIS
     newfs [-NOU] [-S sector-size] [-T disktype] [-a maxcontig]
	   [-b block-size] [-c cylinders] [-d rotdelay]	[-e maxbpg]
	   [-f frag-size] [-g avgfilesize] [-h avfpdir]	[-i bytes] [-k skew]
	   [-l interleave] [-m free space] [-n rotational positions]
	   [-o optimization] [-p sectors] [-r revolutions] [-s size]
	   [-t tracks] [-u sectors] [-v] [-x sectors] special
     mount_mfs [-NU] [-F file] [-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 is used to initialize and clear filesystems before first use.
     Before running newfs or mount_mfs,	the disk must be labeled using
     disklabel(8).  Newfs builds a file	system on the specified	special	file.
     (We often refer to	the ``special file'' as	the ``disk'', although the
     special file need not be a	physical disk.	In fact, it need not even be
     special.)	Typically the defaults are reasonable, however newfs has
     numerous options to allow the defaults to be selectively 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:

     -T	disktype
	     For backward compatibility	and for	mount_mfs.

     -F	file
	     Mount_mfs will use	this file for the image	of the filesystem.
	     When mount_mfs exits, this	file will be left behind.

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

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

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

     -U	     Enables soft updates on the new filesystem.

     -a	maxcontig
	     Specify the maximum number	of contiguous blocks that will be laid
	     out before	forcing	a rotational delay (see	the -d option).	 The
	     default value is 1.  See tunefs(8)	for more details on how	to set
	     this option.

     -b	block-size
	     The block size of the file	system,	in bytes.  It must be a	power
	     of	2.  The	default	size is	16384 bytes, and the smallest allow-
	     able size is 4096 bytes.  The optimal block:fragment ratio	is
	     8:1.  Other ratios	are possible, but are not recommended, and may
	     produce unpredictable results.

     -c	#cylinders/group
	     The number	of cylinders per cylinder group	in a file system.  The
	     default is	to compute the maximum allowed by the other parame-
	     ters.  This value is dependent on a number	of other parameters,
	     in	particular the block size and the number of bytes per inode.

     -d	rotdelay
	     This parameter once specified the minimum time in milliseconds
	     required to initiate another disk transfer	on the same cylinder.
	     It	was used in determining	the rotationally optimal layout	for
	     disk blocks within	a file.	 Modern	disks with read/write-behind
	     achieve higher performance	with this feature disabled, so this
	     value should be left at the default value of 0 milliseconds.  See
	     tunefs(8) for more	details	on how to set this option.

     -e	maxbpg
	     Indicate the maximum number of blocks any single file can allo-
	     cate out of a cylinder group before it is forced to begin allo-
	     cating blocks from	another	cylinder group.	 The default is	about
	     one quarter of the	total blocks in	a cylinder 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.  It	must be	a
	     power of two ranging in value between blocksize/8 and blocksize.
	     The default is 2048 bytes.

     -g	avgfilesize
	     The expected average file size for	the file system.

     -h	avgfpdir
	     The expected average number of files per directory	on the file
	     system.

     -i	number of bytes	per inode
	     Specify the density of inodes in the file system.	The default is
	     to	create an inode	for every (4 * frag-size) 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.  One inode
	     is	required for each distinct file, so this value effectively
	     specifies the average file	size on	the file system.

     -m	free space %
	     The percentage of space reserved from normal users; the minimum
	     free space	threshold.  The	default	value used is defined by
	     MINFREE from <ufs/ffs/fs.h>, currently 8%.	 See tunefs(8) for
	     more details on how to set	this option.

     -n	number of distinguished	rotational positions
	     UFS has the ability to keep track of the availability of blocks
	     at	different rotational positions,	so that	it could lay out the
	     data to be	picked up with minimum rotational latency.  This
	     parameter specifies the default number of rotational positions to
	     distinguish.

	     Nowadays this value should	be set to 1 (which essentially dis-
	     ables the rotational position table) because modern drives	with
	     read-ahead	and write-behind do better without the rotational
	     position table.

     -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	mini-
	     mize the space fragmentation on the disk.	If the value of	min-
	     free (see above) is less than 8%, the default is to optimize for
	     space; if the value of minfree is greater than or equal to	8%,
	     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.  This value defaults to
	     the size of the raw partition specified in	special	(in other
	     words, newfs will use the entire partition	for the	file system).

     -v	     Specify that the disk does	not contain any	partitions, and	that
	     newfs should build	a file system on the whole disk.  This option
	     is	useful for synthetic disks such	as vinum.

     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(8) 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 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.
	     This option is of historical importance only; modern controllers
	     are always	fast enough to handle operations back-to-back.

     -l	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:
		   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.	This option is of historical importance	only; the
	     physical sector layout of modern disks is not visible from	out-
	     side.

     -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.  This	option is of histori-
	     cal importance only.  Modern disks	perform	their own bad sector
	     allocation.

     -r	revolutions/minute
	     The speed of the disk in revolutions per minute.  This value is
	     no	longer of interest, since all the parameters which depend on
	     it	are usually disabled.

     -t	#tracks/cylinder
	     The number	of tracks/cylinder available for data allocation by
	     the file system.  The default is 1.  If zero is specified,	the
	     value from	the disklabel will be used.

     -u	sectors/track
	     The number	of sectors per track available for data	allocation by
	     the file system.  The default is 4096.  If	zero is	specified, the
	     value from	the disklabel will be used.  This does not include
	     sectors reserved at the end of each track for bad block replace-
	     ment (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 cylinder.	 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.  This option is of historical importance only.
	     Modern disks perform their	own bad	sector 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.

EXAMPLES
	   newfs /dev/ad3s1a

     Creates a new ufs file system on ad3s1a.  newfs will use a	block size of
     16384 bytes, a fragment size of 2048 bytes	and the	largest	possible num-
     ber of cylinders per group.  These	values tend to produce better perfor-
     mance for most applications than the historical defaults (8192 byte block
     size and 1024 byte	fragment size).	 This large fragment size may lead to
     large amounts of wasted space on filesystems that contain a large number
     of	small files.

	   mount_mfs -s	131072 -o nosuid,nodev,nosymfollow /dev/da0s1b /tmp

     Mount a 64	MB large memory	file system on /tmp, with mount(8) options
     nosuid, nodev, and	nosymfollow.

SEE ALSO
     fdformat(1), disktab(5), fs(5), camcontrol(8), disklabel(8), diskpart(8),
     dumpfs(8),	fsck(8), mount(8), tunefs(8), vinum(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.

FreeBSD	9.3		       December	19, 2000		   FreeBSD 9.3

NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | SEE ALSO | HISTORY

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