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

NAME
     newfs, mount_mfs — construct a new UFS file system

SYNOPSIS
     newfs [-L volname] [-NCOU] [-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]
	   [-v] 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.

     mount_mfs creates the raw character device /dev/mfs<PID> to represent the
     backing store while the mount is active.  This device may be read but not
     written and allows swap-based MFS filesystems to be dumped if desired.

     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.

     -C	     Tell Mount_mfs to copy the underlying filesystem into the MFS
	     mount being created over it.

     -L volname
	     Add a volume label to the new file system.

     -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 geometry information from the storage device.

     -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(5) 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 posi‐
	     tions 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.  It may also be used
	     to allow newfs to operate on regular files.  When operating on a
	     regular file, newfs will synthesize a reasonable geometry for the
	     filesystem.

     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 device geometry 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 device geometry will be used.  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 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(5) file system on ad3s1a.  newfs will use a block size
     of 16384 bytes, a fragment size of 2048 bytes and the largest possible
     number of cylinders per group.  These values tend to produce better per‐
     formance 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), UFS(5), disktab(5), fs(5), camcontrol(8), disklabel(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.

BSD			       November 24, 2010			   BSD
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