freebsd-nq/sbin/newfs/newfs.8

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.\"     @(#)newfs.8	8.6 (Berkeley) 5/3/95
.\" $FreeBSD$
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.Dd May 18, 2002
.Dt NEWFS 8
.Os
.Sh NAME
.Nm newfs ,
.Nd construct a new filesystem
.Sh SYNOPSIS
.Nm
.Op Fl NU
.Op Fl O Ar filesystem-type
.Op Fl S Ar sector-size
.Op Fl T Ar disktype
.Op Fl a Ar maxcontig
.Op Fl b Ar block-size
.Op Fl c Ar blocks-per-cylinder-group
.Op Fl d Ar max-extent-size
.Op Fl e Ar maxbpg
.Op Fl f Ar frag-size
.Op Fl g Ar avgfilesize
.Op Fl h Ar avfpdir
.Op Fl i Ar bytes
.Op Fl m Ar free space
.Op Fl o Ar optimization
.Op Fl s Ar size
.Ar special
.Sh DESCRIPTION
.Nm Newfs
is used to initialize and clear filesystems before first use.
Before running
.Nm
the disk must be labeled using
.Xr disklabel 8 .
.Nm Newfs
builds a filesystem on the specified special file.
(We often refer to the
.Dq special file
as the
.Dq 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
.Nm
has numerous options to allow the defaults to be selectively overridden.
.Pp
The following options define the general layout policies:
.Bl -tag -width indent
.It Fl T Ar disktype
For backward compatibility.
.It Fl N
Cause the filesystem parameters to be printed out
without really creating the filesystem.
.It Fl O
Use 1 to specify that a UFS1 format filesystem be built;
use 2 to specify that a UFS2 format filesystem be built.
The default is UFS1 format, but will eventually be changed to UFS2.
.It Fl U
Enables soft updates on the new filesystem.
.It Fl a Ar maxcontig
Specify the maximum number of contiguous blocks that will be
laid out before forcing a rotational delay.
The default value is 16.
See
.Xr tunefs 8
for more details on how to set this option.
.It Fl b Ar block-size
The block size of the filesystem, in bytes.  It must be a power of 2.  The
default size is 16384 bytes, and the smallest allowable size is 4096 bytes.
The optimal block:fragment ratio is 8:1.
Other ratios are possible, but are not recommended,
and may produce poor results.
.It Fl c Ar number of blocks per cylinders group
The number of blocks per cylinder group in a filesystem.  The default
is to compute the maximum allowed by the other parameters.  This value is
dependent on a number of other parameters, in particular the block size
and the number of bytes per inode.
.It Fl d Ar max extent size
The filesystem may choose to store large files using extents.
This parameter specifies the largest extent size that may be used.
It is presently limited to its default value which is 16 times
the filesystem blocksize.
.It Fl e Ar maxbpg
Indicate 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 cylinder group.
See
.Xr tunefs 8
for more details on how to set this option.
.It Fl f Ar frag-size
The fragment size of the filesystem in bytes.  It must be a power of two
ranging in value between
.Ar blocksize Ns /8
and
.Ar blocksize .
The default is 2048 bytes.
.It Fl g Ar avgfilesize
The expected average file size for the filesystem.
.It Fl h Ar avgfpdir
The expected average number of files per directory on the filesystem.
.It Fl i Ar number of bytes per inode
Specify the density of inodes in the filesystem.
The default is to create an inode for every
.Pq 4 * Ar 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 filesystem.
.It Fl m Ar free space \&%
The percentage of space reserved from normal users; the minimum free
space threshold.
The default value used is
defined by
.Dv MINFREE
from
.Aq Pa ufs/ffs/fs.h ,
currently 8%.
See
.Xr tunefs 8
for more details on how to set this option.
.It Fl o Ar optimization\ preference
.Pq Ar space No or Ar time .
The filesystem 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 8%,
the default is to optimize for
.Ar space ;
if the value of minfree is greater than or equal to 8%,
the default is to optimize for
.Ar time .
See
.Xr tunefs 8
for more details on how to set this option.
.It Fl s Ar size
The size of the filesystem in sectors.  This value defaults to the size of the
raw partition specified in
.Ar special
(in other words,
.Nm
will use the entire partition for the filesystem).
.El
.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
to build a filesystem 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 8
to find the alternate superblocks if the standard superblock is lost.
.Bl -tag -width indent
.It Fl S Ar sector-size
The size of a sector in bytes (almost never anything but 512).
.El
.Sh EXAMPLES
.Dl newfs /dev/ad3s1a
.Pp
Creates a new ufs filesystem on
.Pa ad3s1a .
.Nm
will use a block size of 16384 bytes, a fragment size of 2048 bytes
and the largest possible number of blocks per cylinders group.
These values tend to produce better performance for most applications
than the historical defaults
(8192 byte block size and 1024 byte fragment size).
This large fragment size may lead to much wasted space
on filesystems that contain many small files.
.Sh SEE ALSO
.Xr fdformat 1 ,
.Xr disktab 5 ,
.Xr fs 5 ,
.Xr camcontrol 8 ,
.Xr disklabel 8 ,
.Xr diskpart 8 ,
.Xr dumpfs 8 ,
.Xr fsck 8 ,
.Xr mount 8 ,
.Xr tunefs 8 ,
.Xr vinum 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 .