.\"	$NetBSD: newfs_lfs.8,v 1.23 2014/01/04 15:35:10 wiz Exp $
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.\" Copyright (c) 1993
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.\"     @(#)newlfs.8	8.1 (Berkeley) 6/19/93
.\"
.Dd July 12, 2001
.Dt NEWFS_LFS 8
.Os
.Sh NAME
.Nm newfs_lfs
.Nd construct a new LFS file system
.Sh SYNOPSIS
.Nm
.Op Ar newfs_lfs-options
.Ar special
.Sh DESCRIPTION
.Nm
builds a log-structured file system on the specified special
device basing its defaults on the information in the disk label.
Before running
.Nm
the disk must be labeled using
.Xr disklabel 8 ,
the proper fstype is 4.4LFS.
Reasonable values for the
.Li fsize ,
.Li bsize ,
and
.Li sgs
fields are 1024, 8192, and 7 respectively.
.Pp
The following options define the general layout policies.
.Bl -tag -width Fl
.It Fl A
Attempt to compute the appropriate segment size using the formula
.Em 4 * bandwidth * access time .
The disk is tested for twenty seconds
to discover its bandwidth and seek time.
.It Fl B Ar logical-segment-size
The logical segment size of the file system in bytes.
If not specified, the segment size is computed by left-shifting
the partition label's block size by the amount indicated in the
partition table's segshift.
If the disklabel indicates a zero block size or segment shift,
a compile-time default segment size of 1M is used.
.It Fl b Ar block-size
The block size of the file system in bytes.
If not specified, the block size is taken from the partition label,
or if the partition label indicates 0,
a compile-time default of 8K is used.
.It Fl F
Force creation of an LFS even on a partition labeled as another type.
.Nm
will use compile-time default values for block and fragment size, and segment
shift, unless these are overridden by command-line flags.
.It Fl f Ar fragment-size
The fragment size of the file system in bytes.
If not specified, the fragment size is taken from the partition label,
or if the partition label indicates 0,
a compile-time default of 1K is used.
.It Fl I Ar interleave
Specify the interleave between segments.
The default is zero.
.It Fl i
The size of an inode block, in bytes.
The default is to use the same size as a fragment,
or in a v1 filesystem, the same size as a data block.
.It Fl L
Create a log-structured file system (LFS).
This is the default, and this
option is provided for compatibility only.
.It Fl M Ar nsegs
Specify
.Em lfs_minfreeseg ,
the number of segments left out of the amount allocated to user data.
A higher number increases cleaner performance, while a lower number
gives more usable space.
The default is based on the size of the filesystem, either 5% of the
total number of segments or 20 segments, whichever is larger.
.It Fl m Ar free space \&%
The percentage of space reserved from normal users; the minimum
free space threshold.
The default value used is 10%.
.It Fl N
Do not actually create the filesystem.
.It Fl O Ar offset
Start the first segment this many sectors from the beginning of the
partition.
The default is zero.
.It Fl R Ar nsegs
Specify
.Em lfs_resvseg ,
the number of segments set aside for the exclusive use of the cleaner.
A larger figure reduces the likelihood of running out of clean segments,
but if
.Em lfs_resvseg
is too close to
.Em lfs_minfreeseg ,
the cleaner will run without ceasing when the filesystem becomes close to
full.
The default is the larger of 15 or the quantity
.Em lfs_minfreeseg
/ 2 + 1 .
.It Fl r Ar ident
For a v2 filesystem, specify the roll-forward identifier for the
filesystem.
This identifier, a 32-bit numeric quantity,
should be different from that of any LFS that may previously
have existed on the same disk.
By default the identifier is chosen at random.
.It Fl s Ar size
The size of the file system in sectors.
.It Fl v Ar version
Make a filesystem with the specified disk layout version.
Valid options are 1 or 2 (the default).
.Em Note ,
however, that LFS version 1 is deprecated.
.El
.Sh SEE ALSO
.Xr disktab 5 ,
.\" .Xr fs 5 ,
.Xr disklabel 8 ,
.Xr diskpart 8 ,
.Xr dumplfs 8
.\" .Xr tunefs 8
.Rs
.%A M. Seltzer
.%A K. Bostic
.%A M. McKusick
.%A C. Staelin
.%T "An Implementation of a Log-Structured File System for UNIX"
.%J "Proceedings of the Winter 1993 USENIX Conference"
.%D January 25-29, 1993
.%P pp. 315-331
.Re
.Rs
.%A J. Matthews
.%A D. Roselli
.%A A. Costello
.%A R. Wang
.%A T. Anderson
.%T "Improving the Performance of Log-Structured File Systems with Adaptive Methods"
.%J "Proceedings of the Sixteenth ACM SOSP"
.%D October 1997
.Re
.Sh HISTORY
A
.Ic newlfs
command appeared in
.Bx 4.4 ,
and was renamed to
.Nm
for
.Nx 1.4 .