NAME
newfs
, mount_mfs
— construct a new file
system
SYNOPSIS
newfs |
[-Nq ]
[-b block-size]
[-c fragments-per-cylinder-group]
[-e maxbpg]
[-f frag-size]
[-g avgfilesize]
[-h avgfpdir]
[-i bytes]
[-m free-space]
[-O filesystem-format]
[-o optimization]
[-S sector-size]
[-s size]
[-T disktype]
[-t fstype] special |
mount_mfs |
[-b block-size]
[-c fragments-per-cylinder-group]
[-e maxbpg]
[-f frag-size]
[-i bytes]
[-m free-space]
[-o options]
[-P file]
[-s size] special
node |
DESCRIPTION
Before running newfs
, 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.
The special file should be a raw device, for example /dev/rsd0a; if a relative path like sd0a is specified, the corresponding raw device is used.
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) built in, 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 options to newfs
are as follows:
-b
block-size- The block size of the file system, in bytes. If a disklabel is available, the default is read from it. Otherwise the default is 16 KB or eight times the fragment size, whichever is smaller.
-c
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.
-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. If a disklabel is available, the default is read from it. Otherwise 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
bytes- This specifies the density of inodes in the file system. The default is to create an inode for every 4 fragments, for 4k disks one inode for every 2 fragments. 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 file system parameters to be printed out without really creating the file system.
-O
filesystem-format- Select the filesystem format:
- 0
- 4.3BSD format file system. This option is primarily used to build root file systems that can be understood by older boot ROMs.
- 1
- Fast File System (FFS).
- 2
- Enhanced Fast File System (FFS2), the default.
-o
optimization- 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.
-q
- Operate in quiet mode. With this option,
newfs
will not print extraneous information like superblock backups. -S
sector-size- The size of a sector in bytes (almost always 512). Alternatively
sector-size may instead use a multiplier, as
documented in
scan_scaled(3). sector-size should be
512 or a multiple of it because the kernel operates 512-byte blocks
internally. A sector is the smallest addressable unit on the physical
device. Changing this 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 this from its default will make it impossible for fsck(8) to find the alternate superblocks automatically if the standard superblock is lost. -s
size- The size of the file system in sectors (see
-S
). Alternatively size may instead use a multiplier, as documented in scan_scaled(3), to specify size in bytes; in this case size is rounded up to the next sector boundary. The maximum size of an FFS file system is 2,147,483,647 (2^31 - 1) of 512-byte blocks, slightly less than 1 TB. FFS2 file systems can be as large as 64 PB. Note however that formount_mfs
the practical limit is based on datasize in login.conf(5), and ultimately depends on the per-archMAXDSIZ
limit. -T
disktype- Uses information for the specified disk from disktab(5) instead of trying to get the information from the disklabel(5).
-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.
The options to mount_mfs
are as described
for newfs
, except for the -o
and -P
options.
Those options are as follows:
-o
options- 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. -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.
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.
ENVIRONMENT
COLUMNS
- If set to a positive integer, output is formatted to the given width in
columns. Otherwise,
newfs
defaults to the terminal width, or 80 columns if the output is not a terminal.
SEE ALSO
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).
M. McKusick, M. Karels, and K. Bostic, A Pageable Memory Based Filesystem, USENIX Summer Conference Proceedings, 1990.
HISTORY
The newfs
command appeared in
4.2BSD.