NEWFS(8)NEWFS(8)NAME
newfs, mfs - construct a new file system
SYNOPSISnewfs [ -N ] [ newfs-options ] special
mfs [ -F mount_flags ] [ newfs-options ] special node
DESCRIPTION
Newfs replaces the more obtuse mkfs(8) program. Before running newfs
or 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. The -N option causes the file system parameters to
be printed out without really creating the file system.
Mfs is used to build a file system in virtual memory and then mount it
on a specified node. Mfs exits and the contents of the file system are
lost when the file system is unmounted. If mfs is sent a signal while
running, for example during system shutdown, it will attempt to unmount
its corresponding file system. The parameters to mfs are the same as
those to newfs. The special file 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.
-b block-size
The block size of the file system in bytes.
-f frag-size
The fragment size of the file system in bytes.
-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.
-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 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.
-a maxcontig
This specifies the maximum number of contiguous blocks that
will be laid out before forcing a rotational delay (see -d
below). The default value is one. See tunefs(8) for more
details on how to set this option.
-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.
-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.
-c #cylinders/group
The number of cylinders per cylinder group in a file system.
The default value used is 16.
-s size The size of the file system in sectors.
The following options override the standard sizes for the disk geome‐
try. 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 impossible for fsck to find the alternate superblocks if
the standard super block is lost.
-r revolutions/minute
The speed of the disk in revolutions per minute.
-S sector-size
The size of a sector in bytes (almost never anything but
512).
-u sectors/track
The number of sectors/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 -p
below).
-t #tracks/cylinder
The number of tracks/cylinder available for data allocation
by the file system.
-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.
-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.
-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.
-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.
The following option applies only to mfs.
-F 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 mfs is started by
the mount(8) command.
SEE ALSOdisktab(5), fs(5), disklabel(8), diskpart(8), fsck(8), format(8),
tunefs(8)
M. McKusick, W. Joy, S. Leffler, R. Fabry, ``A Fast File System for
UNIX'', ACM Transactions on Computer Systems 2, 3. pp 181-197, August
1984. (reprinted in the System Manager's Manual, SMM:14)
4.2 Berkeley Distribution June 24, 1990 NEWFS(8)
