newfs(8)
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NEWFS(8) NetBSD System Manager's Manual NEWFS(8)
NAME
newfs, mount_mfs - construct a new file system
SYNOPSIS
newfs [-B byte order] [-NO] [-S sector-size] [-T disktype] [-a maxcontig]
[-b block-size] [-c cylinders] [-d rotdelay] [-e maxbpg] [-f
frag-size] [-i bytes] [-k skew] [-l interleave] [-m free space] [-n
rotational positions] [-o optimization] [-p sectors] [-r
revolutions] [-s size] [-t tracks] [-u sectors] [-x sectors]
special
mount_mfs [-N] [-T disktype] [-a maxcontig] [-b block-size] [-c
cylinders] [-d rotdelay] [-e maxbpg] [-f frag-size] [-i bytes] [-m
free space] [-n rotational positions] [-o options] [-s size]
special node
DESCRIPTION
newfs replaces the more obtuse mkfs program. 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,
however newfs has numerous options to allow the defaults to be selective-
ly 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 at-
tempt to unmount its corresponding file system. The parameters to
mount_mfs are the same as those to newfs. If the -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 mount_mfs on a machine without any disks).
The following options define the general layout policies.
-B specify the metadata byte order of the filesystem to be cre-
ated. Valid byte orders are `be' and `le'. If no byte order
is specified, the filesystem is created in host byte order.
-N Causes the file system parameters to be printed out without
really creating the file system.
-O Creates a 4.3BSD format filesystem. This options is primari-
ly used to build root filesystems that can be understood by
older boot ROMs.
-T Uses information for the specified disk from /etc/disktab in-
stead of trying to get the information from a disklabel.
-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 is 8. See tunefs(8) for more
details on how to set this option.
-b block-size
The block size of the file system, in bytes.
-c #cylinders/group
The number of cylinders per cylinder group in a file system.
The default value is 16.
-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 de-
fault is about one quarter of the total blocks in a cylinder
group. See tunefs(8) for more details on how to set this op-
tion.
-f frag-size
The fragment size of the file system in bytes.
-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 mini-
mum free space threshold. The default value used is 5%. See
tunefs(8) for more details on how to set this option.
-n rotational positions
Determines how many rotational time slots there are in one
revolution of the disk.
-o optimization preference
(``space'' or ``time'') The file system can either be in-
structed 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 de-
fault 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 op-
tion.
-s size The size of the file system in sectors.
The following options override the standard sizes for the disk geometry.
Their default values are taken from the disk label. Changing these de-
faults 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 impos-
sible for fsck_ffs(8) to find the alternative 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 compen-
sate for a slow controller. Track skew is the offset of sec-
tor 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 compen-
sate 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.
-t #tracks/cylinder
The number of tracks/cylinder available for data allocation
by the file system.
-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 cylin-
der. 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 com-
mand, except for the -o option.
That option is as follows:
-o Options are specified with a -o flag followed by a comma separat-
ed string of options. See the mount(8) man page for possible op-
tions and their meanings.
NOTES
If the file system will be exported over NFS, the fsirand(8) utility
should be run after newfs to improve security.
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.
For the newfs command to succeed, the disklabel should first be updated
such that the fstype field for the partition is set to 4.2BSD.
SEE ALSO
disktab(5), fs(5), dumpfs(8), disklabel(8), diskpart(8), format(8),
fsck_ffs(8), fsirand(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).
HISTORY
The newfs command appeared in 4.2BSD.
4.2 Berkeley Distribution May 6, 1998 3
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