MKFS(8) System Manager's Manual MKFS(8)NAME
mkfs - construct a file system
/sbin/mkfs [ -i bytes ] [ -s size ] [ -m gap ] [ -n modulus ] special
N.B.: file systems are normally created with the newfs(8) command.
Mkfs constructs a file system by writing on the special file special. The size of the filesystem in logical blocks is specified by the -s
size option. Logical blocks are 1K (2 sectors) under 2.11BSD.
NOTE: The newfs(8) program's -s option is in units of sectors. Newfs(8) converts this to filesystem (logical) blocks for mkfs(8).
The number of inodes is calculated based on the argument bytes to the -i option. The default is 4096. If more inodes are desired in a
filesystem (there is an absolute maximum of 65500) then a lower value for bytes should be used, perhaps 3072 or even 2048.
The flags -m gap and -n modulus determine the block interleaving of the freelist that will be constructed, where gap is the distance
between successive 1024-byte blocks, and modulus is the number of blocks before the pattern repeats, typically one cylinder. The optimal
values for these parameters vary with the speed and geometry of the disk, as well as the speed of the processor. Newfs(8) will calculate
the correct values in almost all cases from the disklabel.
SEE ALSO fs(5), dir(5), disklabel(8), fsck(8), mkproto(8)newfs(8)BUGS
The lost+found directory is created but the boot block is left uninitialized (see disklabel(8).)
3rd Berkeley Distribution November 16, 1996 MKFS(8)
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NEWFS(8) BSD System Manager's Manual NEWFS(8)NAME
newfs -- construct a new file system
newfs [-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
Newfs replaces the more obtuse mkfs(8) program. Before running newfs the disk must be labeled using disklabel(8). Newfs builds a file sys-
tem 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 selectively overridden.
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 filesystem. This options is primarily used to build root filesystems that can be understood by older
-T Uses information for the specified disk from /etc/disktab instead of trying to get the information from a disklabel.
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 one. See tunefs(8) for more details on how to set this option.
The block size of the file system, in bytes.
The number of cylinders per cylinder group in a file system. The default value is 16.
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 4 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.
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 2048 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 10%. 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 instructed 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 10%, the default is to opti-
mize for space; if the value of minfree is greater than or equal to 10%, 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 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 to find the alternate superblocks if the standard superblock is lost.
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
-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.
The speed of the disk in revolutions per minute.
The number of tracks/cylinder available for data allocation by the file system.
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.
SEE ALSO fs(5), dumpfs(8), fdisk(8), fsck(8), mount(8), pdisk(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.
4.2 Berkeley Distribution May 3, 1995 4.2 Berkeley Distribution