newfs
NEWFS(8) OpenBSD System Manager's Manual NEWFS(8)
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 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.
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. 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), the default for file
systems smaller than 1 TB.
2 Enhanced Fast File System (FFS2), the default for
file systems larger than 1 TB.
-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 for
mount_mfs the practical limit is based on datasize in
login.conf(5), and ultimately depends on the per-arch MAXDSIZ
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
TMPDIR Directory in which to create temporary mount points for use by
mount_mfs -P instead of /tmp.
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.
OpenBSD 5.1 May 23, 2011 OpenBSD 5.1
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