freebsd-dev/sbin/newfs/newfs.8

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.\"     @(#)newfs.8	8.6 (Berkeley) 5/3/95
.\" $FreeBSD$
.\"
.Dd March 21, 2008
.Dt NEWFS 8
.Os
.Sh NAME
.Nm newfs
.Nd construct a new UFS1/UFS2 file system
.Sh SYNOPSIS
.Nm
.Op Fl EJNUln
.Op Fl L Ar volname
.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 avgfpdir
.Op Fl i Ar bytes
.Op Fl m Ar free-space
.Op Fl o Ar optimization
.Op Fl p Ar partition
.Op Fl r Ar reserved
.Op Fl s Ar size
.Ar special
.Sh DESCRIPTION
The
.Nm
utility is used to initialize and clear file systems before first use.
The
.Nm
utility builds a file system 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 E
Erase the content of the disk before making the filesystem.
The reserved area in front of the superblock (for bootcode) will not be erased.

This is a relevant option for flash based storage devices that use
wear levelling algorithms.

NB: Erasing may take as long time as writing every sector on the disk.
.It Fl J
Enable journaling on the new file system via gjournal.
.It Fl L Ar volname
Add a volume label to the new file system.
.It Fl N
Cause the file system parameters to be printed out
without really creating the file system.
.It Fl O Ar filesystem-type
Use 1 to specify that a UFS1 format file system be built;
use 2 to specify that a UFS2 format file system be built.
The default format is UFS2.
.It Fl T Ar disktype
For backward compatibility.
.It Fl U
Enable soft updates on the new file system.
.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 file system, 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 blocks-per-cylinder-group
The number of blocks per cylinder group in a file system.
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 file system 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 file system 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 file system 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 file system.
.It Fl h Ar avgfpdir
The expected average number of files per directory on the file system.
.It Fl i Ar bytes
Specify the density of inodes in the file system.
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 file system.
.It Fl l
Enable multilabel MAC on the new file system.
.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
.In ufs/ffs/fs.h ,
currently 8%.
See
.Xr tunefs 8
for more details on how to set this option.
.It Fl n
Do not create a
.Pa .snap
directory on the new file system.
The resulting file system will not support snapshot generation, so
.Xr dump 8
in live mode and background
.Xr fsck 8
will not function properly.
The traditional
.Xr fsck 8
and offline
.Xr dump 8
will work on the file system.
This option is intended primarily for memory or vnode-backed file systems that
do not require
.Xr dump 8
or
.Xr fsck 8
support.
.It Fl o Ar optimization
.Cm ( space
or
.Cm 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 8%,
the default is to optimize for
.Cm space ;
if the value of minfree is greater than or equal to 8%,
the default is to optimize for
.Cm time .
See
.Xr tunefs 8
for more details on how to set this option.
.It Fl p Ar partition
The partition name (a..h) you want to use in case the underlying image
is a file, so you don't have access to individual partitions through the
filesystem.
Can also be used with a device, e.g.
.Nm
.Fl p Ar f
.Ar /dev/da1s3
is equivalent to
.Nm
.Ar /dev/da1s3f .
.It Fl r Ar reserved
The size, in sectors, of reserved space
at the end of the partition specified in
.Ar special .
This space will not be occupied by the file system;
it can be used by other consumers such as
.Xr geom 4 .
Defaults to 0.
.It Fl s Ar size
The size of the file system in sectors.
This value defaults to the size of the
raw partition specified in
.Ar special
less the
.Ar reserved
space at its end (see
.Fl r ) .
A
.Ar size
of 0 can also be used to choose the default value.
A valid
.Ar size
value cannot be larger than the default one,
which means that the file system cannot extend into the reserved space.
.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 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
.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 file system on
.Pa ad3s1a .
The
.Nm
utility 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 file systems that contain many small files.
.Sh SEE ALSO
.Xr fdformat 1 ,
.Xr geom 4 ,
.Xr disktab 5 ,
.Xr fs 5 ,
.Xr bsdlabel 8 ,
.Xr camcontrol 8 ,
.Xr dump 8 ,
.Xr dumpfs 8 ,
.Xr fsck 8 ,
.Xr mount 8 ,
.Xr tunefs 8 ,
.Xr gvinum 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
utility appeared in
.Bx 4.2 .