NEWFS(8) BSD System Manager's Manual NEWFS(8)
newfs, mount_mfs - construct a new filesystem
newfs [-NOq] [-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] [-r revolutions] [-S sector-size]
[-s size] [-t fstype] [-u sectors] [-x sectors] [-z tracks] special
mount_mfs [-a maxcontig] [-b block-size] [-c cylinders] [-d rotdelay]
[-e maxbpg] [-f frag-size] [-i bytes] [-m free space] [-o options]
[-P file] [-s size] special node
Before running newfs or mount_mfs, the disk must be labeled using
disklabel(8). newfs builds a filesystem 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 filesystem in virtual memory and then mount
it on a specified node. mount_mfs exits and the contents of the filesys-
tem are lost when the filesystem is unmounted. If mount_mfs is sent a
signal while running, for example during system shutdown, it will attempt
to unmount its corresponding filesystem. 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 filesystem. The special file is typically that of the pri-
mary swap area, since that is where the filesystem will be backed up when
free memory gets low and the memory supporting the filesystem has to be
paged. If the keyword "swap" is used instead of a special file name, de-
fault 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) built
in, so it is not necessary to run fsirand(8) manually unless you wish to
re-randomize the filesystem (or list the inode generation numbers).
The following options define the general layout policies:
-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 filesystem, in bytes. The default is
16KB.
-c cylinders
The number of cylinders per cylinder group in a filesystem.
The default is to use as many as fit with the other parame-
ters 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 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 filesystem in bytes. The default is
2048.
-g avgfilesize
The expected average file size for the filesystem in bytes.
-h avgfpdir
The expected average number of files per directory on the
filesystem.
-i bytes This specifies the density of inodes in the filesystem. 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.
-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 Causes the filesystem parameters to be printed out without
really creating the filesystem.
-n nrpos The number of distinct rotational positions. The default is
1.
-O Creates a 4.3BSD format filesystem. This option is primarily
used to build root filesystems that can be understood by old-
er boot ROMs.
-o optimization
space or time. The filesystem 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 op-
timization 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 de-
tails on how to set this option.
-q Operate in quiet mode. With this option, newfs will not print
extraneous information like superblock backups.
-s size The size of the filesystem in sectors. The maximum size of a
filesystem 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 de-
faults is useful only when using newfs to build a filesystem 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(8) to find the alternate superblocks if the standard su-
perblock is lost.
-k skew 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 interleave
Used to describe perturbations in the media format to compen-
sate for a slow controller. Interleave is physical sector in-
terleave 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 sectors 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 filesystem for data allocation.
-r revolutions
The speed of the disk in revolutions per minute.
-S sector-size
The size of a sector in bytes (almost never anything but
512).
-t fstype Set the filesystem type of which filesystem you wish to
create. newfs will be smart enough to run the alternate
newfs_XXX program instead.
-u sectors 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 sectors 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.
-z tracks The number of tracks/cylinder available for data allocation
by the file system.
The options to the mount_mfs command are as described for the newfs com-
mand, except for the -o and -P options.
These options are as follows:
-o options
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.
-P file
If file is a directory, populate the created mfs filesystem with
the contents of the directory. If file is a block device, popu-
late the created mfs filesystem with the contents of the FFS
filesystem contained on the device.
If the -P file option is not used, the owner and mode of the created mfs
filesystem 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 Filesystem 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.
MirBSD #10-current March 27, 1994 3