mkfs(1M-ufs) mkfs(1M-ufs)
NAME
mkfs (ufs) - construct a ufs file system
SYNOPSIS
mkfs [-F ufs] [genericoptions] [-o specificoptions] special size
DESCRIPTION
NOTE: Since the mkfs command is awkward to use, it is suggested that
the newfs(1M) command be used to create ufs file systems. The
newfs command determines the mkfs parameters by obtaining the
information directly from the disk drive specified via special.
See the newfs(1M) manual page for more information.
mkfs constructs a file system by writing to the special file special
unless the -o N flag has been specified. special must be a character
special device file (for example, /dev/ios0/rsdisk000s1). The numeric
size size (maximum <= partition size) specifies the number of sectors
in the file system. mkfs builds a file system with a root directory
and a lost+found directory [see fsck(1M)]. The number of inodes is
calculated as a function of the file system size.
If additional arguments are given, then they are identical to the
values specified via the -o option described below. If no other argu-
ments are given, mkfs will use a set of internal defaults to create a
file system. This is not recommended, since the internal defaults will
undoubtedly be incorrect for the supplied disks.
OPTIONS
-F ufs Specifies the ufs-FSType.
genericoptions Options supported by the generic mkfs command.
-o Specifies the ufs specific suboptions. The following
suboptions are available:
N The file system is not written to the
special file. This suboption gives all
the information as if the file system
was created, but it does not create it.
nsect=n The number of sectors per track on the
disk. The default is 18.
ntrack=n The number of tracks per cylinder on the
disk. The default is 9.
bsize=n The primary block size for files on the
file system. It must be a power of two,
currently selected from 4096, 8192 or
16384. The default is 16384.
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mkfs(1M-ufs) mkfs(1M-ufs)
fragsize=n The fragment size for files on the file
system. The fragsize represents the
smallest amount of disk space that will
be allocated to a file. It must be a
power of two currently selected from the
range 512 to 16384. The default is 2048.
It must be possible to generate a block
number for every fragment. The maximum
block number is 2147483647. A maximum of
8 fragments (in fragsize) can be created
for each block (in bsize).
cgsize=n The number of disk cylinders per
cylinder group. This number must be in
the range 1 to 32. The default is 16.
Further requirements result due to the
concrete physical disk.
minfree=n The minimum percentage of free disk
space allowed. Once the file system
capacity reaches this threshold, only a
privileged user is allowed to allocate
disk blocks. The default value is 10%.
NOTE:
A cylinder group must contain an exact
integer number of file system blocks,
which is directly related to the rota-
tional layout of the physical disk.
rps=n The rotational speed of the disk, in
revolutions per second. The default is
60.
nbpi=n The number of bytes for which one inode
block is allocated. This parameter is
currently set at one inode block for
every 2048 bytes.
NOTE:
If you increase the number of inodes in
the file system, you may also need to
adjust the cgsize and/or bsize parame-
ters since mkfs only administers 2048
inodes per cylinder group. If this is
the case, mkfs outputs an appropriate
message.
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mkfs(1M-ufs) mkfs(1M-ufs)
opt=c Space or time optimization preference; s
specifies optimization for space, t
specifies optimization for time. The
default is t.
apc=n The number of alternates per cylinder.
The default is 0.
gap=n The expected time (in milliseconds) to
service a transfer completion interrupt
and initiate a new transfer on the same
disk. It is used to decide how much
rotational spacing to place between suc-
cessive blocks in a file. (Also known as
rotational delay.) By default, mkfs cal-
culates the best delay based on the disk
type. If the disk type cannot be deter-
mined, then the absolute default is 8.
NOTES
The value of the nbpi operand in the output of mkfs -m is always 2048,
even if the file system was created with some other value.
Some disks may not support a value for nsect less than 2048 bytes.
Some disks may not support the apc parameter.
SEE ALSO
fsck(1M), generic mkfs(1M), newfs(1M), dir(4-ufs), fs(4-ufs).
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