NetBSD/sbin/newfs/newfs.8

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.\"     @(#)newfs.8	8.6 (Berkeley) 5/3/95
.\"
.Dd May 6, 1998
.Dt NEWFS 8
.Os
.Sh NAME
.Nm newfs ,
.Nm mount_mfs
.Nd construct a new file system
.Sh SYNOPSIS
.Nm ""
.Op Fl B Ar byte order
.Op Fl NO
.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 cylinders
.Op Fl d Ar rotdelay
.Op Fl e Ar maxbpg
.Op Fl f Ar frag-size
.Op Fl i Ar bytes
.Op Fl k Ar skew
.Op Fl l Ar interleave
.Op Fl m Ar free space
.Op Fl n Ar rotational positions
.Op Fl o Ar optimization
.Op Fl p Ar sectors
.Op Fl r Ar revolutions
.Op Fl s Ar size
.Op Fl t Ar tracks
.Op Fl u Ar sectors
.Op Fl x Ar sectors
.Ar special
.Nm mount_mfs
.Op Fl N
.Op Fl T Ar disktype
.Op Fl a Ar maxcontig
.Op Fl b Ar block-size
.Op Fl c Ar cylinders
.Op Fl d Ar rotdelay
.Op Fl e Ar maxbpg
.Op Fl f Ar frag-size
.Op Fl i Ar bytes
.Op Fl m Ar free space
.Op Fl n Ar rotational positions
.Op Fl o Ar options
.Op Fl s Ar size
.Ar special node
.Sh DESCRIPTION
.Nm
replaces the more obtuse
mkfs
program.
Before running
.Nm
or
.Nm mount_mfs ,
the disk must be labeled using
.Xr disklabel 8 .
.Nm
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
.Nm
has numerous options to allow the defaults to be selectively overridden.
.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 "" .
If the
.Fl T
flag is specified (see below), the special file is unused.
Otherwise, it 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 ``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
The following options define the general layout policies.
.Bl -tag -width Fl
.It Fl B
Specify the metadata byte order of the filesystem to be created.
Valid byte orders are `be' and `le'.
If no byte order is specified, the filesystem is created in host
byte order.
.It Fl N
Causes the file system parameters to be printed out
without really creating the file system.
.It Fl O
Creates a
.Bx 4.3
format filesystem.
This options is primarily used to build root filesystems
that can be understood by older boot ROMs.
.It Fl T
Uses information for the specified disk from
.Pa /etc/disktab
instead of trying to get the information from a disklabel.
.It Fl a Ar maxcontig
This specifies the maximum number of contiguous blocks that will be
laid out before forcing a rotational delay (see the
.Fl d
option).
The default value is 8.
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 Fl c Ar #cylinders/group
The number of cylinders per cylinder group in a file system.
The default value is 16.
.It Fl d Ar 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 0 milliseconds.
See
.Xr tunefs 8
for more details on how to set this option.
.ne 1i
.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.
.It Fl i Ar number of bytes per inode
This specifies the density of inodes in the file system.
The default is to create an inode for each 4096 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 Ar rotational\ positions
Determines how many rotational time slots there are in
one revolution of the disk.
.It Fl o Ar optimization\ preference
.Pq ``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 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 s Ar size
The size of the file system in sectors.  For
.Nm mount_mfs
an
.Sq m
suffix will be interpreted as a number of megabytes.
.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_ffs 8
to find the alternative superblocks if the standard superblock is lost.
.Bl -tag -width Fl
.It Fl S Ar sector-size
The size of a sector in bytes (almost never anything but 512).
.It Fl k Ar sector \&0 skew , per track
Used to describe perturbations in the media format to compensate for
a slow controller.
Track skew is the offset of sector 0 on track N relative to sector 0
on track N-1 on the same cylinder.
.It Fl l Ar hardware sector interleave
Used to describe perturbations in the media format to compensate for
a slow controller.
Interleave is physical sector interleave on each track,
specified as the denominator of the ratio:
.Dl 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.
.It Fl p Ar 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
.Pq Fl u
since they are not available to the file system for data allocation.
.It Fl r Ar revolutions/minute
The speed of the disk in revolutions per minute.
.ne 1i
.It Fl t Ar #tracks/cylinder
The number of tracks/cylinder available for data allocation by the file
system.
.It Fl u Ar sectors/track
The number of sectors per 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 the
.Fl p
option).
.It Fl x Ar spare sectors per cylinder
Spare sectors (bad sector replacements) are physical sectors that occupy
space at the end of the last track in the cylinder.
They are deducted from the sectors/track
.Pq Fl u
of the last track of each cylinder since they are not available to the file
system for data allocation.
.El
.Pp
The options to the
.Nm mount_mfs
command are as described for the
.Nm
command, except for the
.Fl o
option.
.Pp
That option is as follows:
.Bl -tag -width indent
.It Fl o
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.
.El
.Sh NOTES
If the file system will be exported over NFS, the
.Xr fsirand 8
utility should be run after
.Nm
to improve security.
.Pp
The owner and group ids of the root node of the new filesystem
are set to the effective uid and gid of the user initializing
the filesystem.
.Pp
For the
.Nm
command to succeed,
the disklabel should first be updated such that the fstype field for the
partition is set to
.Bx 4.2 .
.Sh SEE ALSO
.Xr disktab 5 ,
.Xr fs 5 ,
.Xr dumpfs 8 ,
.Xr disklabel 8 ,
.Xr diskpart 8 ,
.\" .Xr format 8 ,
.Xr fsck_ffs 8 ,
.Xr fsirand 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
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.2 .