OpenBSD-4.6/sbin/newfs/newfs.8

.\"	$OpenBSD: newfs.8,v 1.65 2008/08/03 21:43:19 otto Exp $
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.\"     @(#)newfs.8	8.3 (Berkeley) 3/27/94
.\"
.Dd $Mdocdate: August 3 2008 $
.Dt NEWFS 8
.Os
.Sh NAME
.Nm newfs , mount_mfs
.Nd construct a new file system
.Sh SYNOPSIS
.Nm newfs
.Bk -words
.Op Fl Nq
.Op Fl b Ar block-size
.Op Fl c Ar fragments-per-cylinder-group
.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 filesystem-format
.Op Fl o Ar optimization
.Op Fl S Ar sector-size
.Op Fl s Ar size
.Op Fl T Ar disktype
.Op Fl t Ar fstype
.Ar special
.Ek
.Pp
.Nm mount_mfs
.Bk -words
.Op Fl b Ar block-size
.Op Fl c Ar fragments-per-cylinder-group
.Op Fl e Ar maxbpg
.Op Fl f Ar frag-size
.Op Fl i Ar bytes
.Op Fl m Ar free-space
.Op Fl o Ar options
.Op Fl P Ar file
.Op Fl s Ar size
.Ar special node
.Ek
.Sh DESCRIPTION
Before running
.Nm
or
.Nm mount_mfs ,
the disk must be labeled using
.Xr disklabel 8 .
.Nm
builds a file system on the specified
.Ar special
device,
basing its defaults on the information in the disk label.
Typically the defaults are reasonable, although
.Nm
has numerous options to allow the defaults to be selectively overridden.
.Pp
The
.Ar special
file should be a raw device,
for example
.Pa /dev/rsd0a ;
if a relative path like
.Pa sd0a
is specified,
the corresponding raw device is used.
.Pp
.Nm mount_mfs
is used to build a file system in virtual memory and then mount it
on a specified node.
.Nm mount_mfs
exits and the contents of the file system are lost
when the file system is unmounted.
If
.Nm 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
.Nm mount_mfs
are the same as those to
.Nm 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.
If the keyword
.Dq swap
is used instead of a special file name, default configuration parameters
will be used.
(This option is useful when trying to use
.Nm mount_mfs
on a machine without any disks.)
.Pp
Both
.Nm
and
.Nm mount_mfs
now have the functionality of
.Xr fsirand 8
built in, so it is not necessary to run
.Xr fsirand 8
manually unless you wish to re-randomize the
file system (or list the inode generation numbers).
.Pp
The options to
.Nm
are as follows:
.Bl -tag -width Fl
.It Fl b Ar block-size
The block size of the file system, in bytes.
The default is 16KB.
.It Fl c Ar fragments-per-cylinder-group
The number of fragments 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 e Ar 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 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.
The default is 2048.
.It Fl g Ar avgfilesize
The expected average file size for the file system in bytes.
.It Fl h Ar avgfpdir
The expected average number of files per directory on the file system.
.It Fl i Ar bytes
This specifies the density of inodes in the file system.
The default is to create an inode for each 8192 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.
.It Fl m Ar free-space
The percentage of space reserved from normal users; the minimum free
space threshold.
The default value used is 5%.
See
.Xr tunefs 8
for more details on how to set this option.
.It Fl N
Causes the file system parameters to be printed out
without really creating the file system.
.It Fl O Ar filesystem-format
Select the filesystem format:
.Pp
.Bl -tag -width 3n -offset indent -compact
.It 0
.Bx 4.3
format file system.
This option is primarily used to build root file systems that can
be understood by older boot ROMs.
.It 1
Fast File System (the default).
.It 2
Enhanced Fast File System (FFS2).
.El
.It Fl o Ar optimization
.Ar space
or
.Ar 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.
Unless an optimization has been specified,
if the value of minfree (see above) is less than 5%, the default
is to optimize for space; if the value of minfree is greater than
or equal to 5%, the default is to optimize for time.
See
.Xr tunefs 8
for more details on how to set this option.
.It Fl q
Operate in quiet mode.
With this option,
.Nm
will not print extraneous information like superblock backups.
.It Fl S Ar sector-size
The size of a sector in bytes (almost never anything but 512).
Changing this 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 this
from its default will make it impossible for
.Xr fsck 8
to find the alternate superblocks if the standard superblock is
lost.
.It Fl s Ar size
The size of the file system in sectors.
The maximum size of a Fast File
System is 2,147,483,647 (2^31 \- 1) sectors, which is slightly less
than 1TB, assuming a sector size of 512 bytes.
FFS2 file systems can be as large as the maximum partition size supported.
Note however that for
.Nm mount_mfs
the practical limit is based on
.Va datasize
in
.Xr login.conf 5 ,
and ultimately depends on the per-arch
.Dv MAXDSIZ
limit.
.It Fl T Ar disktype
Uses information for the specified disk from
.Xr disktab 5
instead of trying to get the information from the
.Xr disklabel 5 .
.It Fl t Ar fstype
Set the file system type of which file system you wish to create.
.Nm
will be smart enough to run the alternate newfs_XXX program instead.
.El
.Pp
The options to
.Nm mount_mfs
are as described for
.Nm ,
except for the
.Fl o
and
.Fl P
options.
.Pp
Those options are as follows:
.Bl -tag -width indent
.It Fl o Ar options
Options are specified with a
.Fl o
flag followed by a comma separated string of options.
See the
.Xr mount 8
man page for possible options and their meanings.
.It Fl P Ar file
If
.Ar file
is a directory, populate the created mfs file system with the
contents of the directory.
If
.Ar file
is a block device, populate the created mfs file system with the
contents of the FFS file system contained on the device.
.El
.Pp
If the
.Fl P Ar file
option is not used, the owner and mode of the created mfs file
system will be the same as the owner and mode of the mount point.
.Sh ENVIRONMENT
.Bl -tag -width TMPDIR
.It Ev TMPDIR
Directory in which to create temporary mount points for use by
.Nm mount_mfs Fl P
instead of
.Pa /tmp .
.El
.Sh SEE ALSO
.Xr disktab 5 ,
.Xr fs 5 ,
.Xr disklabel 8 ,
.Xr dumpfs 8 ,
.Xr fsck 8 ,
.Xr fsirand 8 ,
.Xr growfs 8 ,
.Xr mount 8 ,
.Xr tunefs 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
.Rs
.%A M. McKusick
.%A M. Karels
.%A K. Bostic
.%T "A Pageable Memory Based Filesystem"
.%J "USENIX Summer Conference Proceedings"
.%D 1990
.Re
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.2 .