newfs, mount_mfs - construct a new file system
newfs [-NO] [-S sector-size] [-a maxcontig] [-b block-size]
[-c cylinders] [-d rotdelay] [-e maxbpg] [-f
frag-size]
[-g avgfilesize] [-h avgfpdir] [-i bytes] [-k skew]
[-l interleave]
[-m free space] [-n nrpos] [-o optimization] [-p
sectors] [-q]
[-r revolutions] [-s size] [-t fstype] [-u sectors]
[-x sectors]
[-z tracks] special
mount_mfs [-P file] [-a maxcontig] [-b block-size] [-c
cylinders]
[-d rotdelay] [-e maxbpg] [-f frag-size] [-i bytes]
[-m free space]
[-o options] [-s size] special node
Before running newfs or mount_mfs, the disk must be labeled
using
disklabel(8). newfs builds a file system on the specified
special device,
basing its defaults on the information in the disk label. Typically
the defaults are reasonable, although newfs has numerous
options to
allow the defaults to be selectively overridden.
mount_mfs is used to build a file system in virtual memory
and then mount
it on a specified node. mount_mfs exits and the contents of
the file
system are lost when the file system is unmounted. If
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
mount_mfs are the same as those to 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 ``swap'' is used instead of
a special
file name, default configuration parameters will be used.
(This option
is useful when trying to use mount_mfs on a machine without
any disks.)
Both newfs and mount_mfs now have the functionality of fsirand(8) builtin
so it is not necessary to run fsirand(8) manually unless
you wish to
re-randomize the file system (or list the inode generation
numbers).
The following options define the general layout policies:
-N Causes the file system parameters to be printed
out without
really creating the file system.
-O Creates a 4.3BSD format file system. This option is primarily
used to build root file systems that can be
understood by
older boot ROMs.
-q Operate in quiet mode. With this option, newfs
will not
print extraneous information like superblock
backups.
-a maxcontig
This specifies the maximum number of contiguous
blocks that
will be laid out before forcing a rotational delay (see the
-d option). The default value depends on the
block size (4
for 16KB blocks, 8 for 8KB blocks, and 16 for
4KB blocks).
See tunefs(8) for more details on how to set
this option.
-b block-size
The block size of the file system, in bytes.
The default is
16KB.
-c #cylinders/group
The number of cylinders per cylinder group in a
file system.
The default is to use as many as fit with the
other parameters
given.
-d 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
tunefs(8) for more details on how to set this
option.
-e 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 tunefs(8) for more details on how to
set this option.
-f frag-size
The fragment size of the file system in bytes.
The default
is 2048.
-g avgfilesize
The expected average file size for the file system in bytes.
-h avgfpdir
The expected average number of files per directory on the
file system.
-i 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.
-m free space %
The percentage of space reserved from normal
users; the minimum
free space threshold. The default value
used is 5%. See
tunefs(8) for more details on how to set this
option.
-n number of rotational positions
The number of distinct rotational positions.
The default is
1.
-o optimization preference
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.
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 tunefs(8)
for more details
on how to set this option.
-s size The size of the file system in sectors. The
maximum size of
a file system is 2,147,483,647 (2^31 - 1) sectors, which is
slightly less than 1TB.
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 newfs 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 fsck(8) to find the alternate superblocks if the
standard superblock
is lost.
-S sector-size
The size of a sector in bytes (almost never anything but
512).
-k 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.
-l 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:
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.
-p 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 (-u) since
they are not
available to the file system for data allocation.
-r revolutions/minute
The speed of the disk in revolutions per minute.
-z #tracks/cylinder
The number of tracks/cylinder available for data
allocation
by the file system.
-t fstype Set the file system type of which file system
you wish to
create. newfs will be smart enough to run the
alternate
newfs_XXX program instead.
-u 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
-p option).
-x 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
(-u) of the
last track of each cylinder since they are not
available to
the file system for data allocation.
The options to the mount_mfs command are as described for
the newfs command,
except for the -P option and the -o option.
These options are as follows:
-P file
If file is a directory, populate the created mfs
file system with
the contents of the directory. If file is a block
device, populate
the created mfs file system with the contents
of the FFS
file system contained on the device.
-o Options are specified with a -o flag followed by a
comma separated
string of options. See the mount(8) man page for
possible options
and their meanings.
If the -P 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.
TMPDIR Directory in which to create temporary mount points
for use by
mount_mfs -P instead of /tmp.
disktab(5), fs(5), disklabel(8), dumpfs(8), fsck(8), fsirand(8),
growfs(8), mount(8), tunefs(8)
M. McKusick, W. Joy, S. Leffler, and R. Fabry, "A Fast File
System for
UNIX", ACM Transactions on Computer Systems 2, 3, pp
181-197, August
1984, (reprinted in the BSD System Manager's Manual).
The newfs command appeared in 4.2BSD.
Certain combinations of block and fragment sizes may not
produce a valid
file system. If a non-default block or fragment size is
specified,
fsck(8) should be run on the newly created filesystem before
use.
OpenBSD 3.6 March 27, 1994
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