mkfs_ufs(1M)
NAME
mkfs_ufs - construct a UFS file system
SYNOPSIS
mkfs -F ufs [generic_options] [-o FSType_specific_options]
raw_device_file [size]
DESCRIPTION
The UFS-specific module of mkfs builds a UFS file system
with a root directory and a lost+found directory (see
fsck(1M)).
The UFS-specific mkfs is rarely run directly. Use the
newfs(1M) command instead.
raw_device_file indicates the disk partition on which to
create the new file system. If the -o N, -V, or -m options
are specified, the raw_device_file is not actually modified.
size specifies the number of disk sectors in the file sys-
tem, where a disk sector is usually 512 bytes. This argument
must follow the raw_device_file argument and is required
(even with -o N), unless the -V or -m generic options are
specified.
generic_options are supported by the generic mkfs command.
See mkfs(1M) for a description of these options.
OPTIONS
The following generic options are supported:
-m Print the command line that was used to create the
existing file system.
-V Print the current mkfs command line.
OPTIONS
The following UFS-specific options are supported:
-o Use one or more of the following values separated by
commas (with no intervening spaces) to specify UFS-
specific options:
apc=n The number of alternate sectors per cylinder to
reserve for bad block replacement for SCSI devices
only. The default is 0.
This option is not applicable for disks with EFI
labels and is ignored.
bsize=n
The logical block size of the file system in bytes,
either 4096 or 8192. The default is 8192. The sun4u
architecture does not support the 4096 block size.
cgsize=n
The number of cylinders per cylinder group, ranging
from 16 to 256. The default is calculated by dividing
the number of sectors in the file system by the number
of sectors in a gigabyte. Then, the result is multi-
plied by 32. The default value is always between 16
and 256.
The per-cylinder-group meta data must fit in a space
no larger than what is available in one logical file
system block. If too large a cgsize is requested, it
is changed by the minimum amount necessary.
fragsize=n
The smallest amount of disk space in bytes that can be
allocated to a file. fragsize must be a power of 2
divisor of bsize, where:
bsize / fragsize is 1, 2, 4, or 8.
This means that if the logical block size is 4096,
legal values for fragsize are 512, 1024, 2048, and
4096. When the logical block size is 8192, legal
values are 1024, 2048, 4096, and 8192. The default
value is 1024.
For file systems greater than 1 terabyte or for file
systems created with the mtb=y option, fragsize is
forced to match block size (bsize).
free=n
The minimum percentage of free space to maintain in
the file system between 0% and 99%, inclusively. This
space is off-limits to users. Once the file system is
filled to this threshold, only the superuser can con-
tinue writing to the file system.
The default is ((64 Mbytes/partition size) * 100),
rounded down to the nearest integer and limited
between 1% and 10%, inclusively.
This parameter can be subsequently changed using the
tunefs(1M) command.
gap=n Rotational delay. This option is obsolete. The value
is always set to 0, regardless of the input value.
maxcontig=n
The maximum number of logical blocks, belonging to one
file, that are allocated contiguously. The default is
calculated as follows:
maxcontig = disk drive maximum transfer size / disk block size
If the disk drive's maximum transfer size cannot be
determined, the default value for maxcontig is calcu-
lated from kernel parameters as follows:
If maxphys is less than ufs_maxmaxphys, which is typi-
cally 1 Mbyte, then maxcontig is set to maxphys. Oth-
erwise, maxcontig is set to ufs_maxmaxphys.
You can set maxcontig to any positive integer value.
The actual value will be the lesser of what has been
specified and what the hardware supports.
You can subsequently change this parameter by using
tunefs(1M).
mtb=y Set the parameters of the file system to allow even-
tual growth to over a terabyte in total file system
size. This option sets fragsize to be the same as
bsize, and sets nbpi to 1 Mbyte, unless the -i option
is used to make it even larger. If you explicitly set
the fragsize or nbpi parameters to values that are
incompatible with this option, the user-supplied value
of fragsize or nbpi is ignored.
N Print out the file system parameters that would be
used to create the file system without actually creat-
ing the file system.
nbpi=n
The number of bytes per inode, which specifies the
density of inodes in the file system. The number is
divided into the total size of the file system to
determine the number of inodes to create.
This value should reflect the expected average size of
files in the file system. If fewer inodes are desired,
a larger number should be used. To create more inodes,
a smaller number should be given. The default is 2048.
The number of inodes can increase if the file system
is expanded with the growfs command.
nrpos=n
The number of different rotational positions in which
to divide a cylinder group. The default is 8.
This option is not applicable for disks with EFI
labels and is ignored.
nsect=n
The number of sectors per track on the disk. The
default is 32.
ntrack=n
The number of tracks per cylinder on the disk. The
default is 16.
This option is not applicable for disks with EFI
labels and is ignored.
opt=s|t
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. The
default is time.
This parameter can be subsequently changed with the
tunefs(1M) command.
rps=n The rotational speed of the disk, in revolutions per
second. The default is 60.
Note that you specify rps for mkfs and rpm for newfs.
This option is not applicable for disks with EFI
labels and is ignored.
Alternatively, parameters can be entered as a list of
space-separated values (without keywords) whose meaning is
positional. In this case, the -o option is omitted and the
list follows the size operand. This is the way newfs passes
the parameters to mkfs.
OPERANDS
The following operands are supported:
raw_device_file
The disk partition on which to write.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWcsu |
|_____________________________|_____________________________|
SEE ALSO
fsck(1M), mkfs(1M), newfs(1M), tunefs(1M), dir_ufs(4),
attributes(5), ufs(7FS)
DIAGNOSTICS
The following error message typically occurs with very high
density disks. On such disks, the file system structure can-
not encode the proper disk layout information. However, such
disks have enough onboard intelligence to make up for any
layout deficiencies, so there is no actual impact on perfor-
mance. The warning that performance might be impaired can
be safely ignored.
Warning: insufficient space in super block for
rotational layout tables with nsect sblock.fs_nsect
and ntrak sblock.fs_ntrak. (File system performance may be impaired.)
The following error message occurs when the disk geometry
results in a situation where the last truncated cylinder
group cannot contain the correct number of data blocks. Some
disk space is wasted.
Warning: inode blocks/cyl group (grp) >= data blocks (num) in last cylinder
The following error message occurs when the best calculated
file system layout is unable to include the last few sectors
in the last cylinder group. This is due to the interaction
between how much space is used for various pieces of meta
data and the total blocks available in a cylinder group.
Modifying nbpi and cpg might reduce this number, but it is
rarely worth the effort.
Warning: num sector(s) in last cylinder group unallocated
NOTES
You can use lofiadm to create a file that appears to the
mkfs command (for example, mkfs_pcfs or mkfs_ufs) as a raw
device. You can then use the mkfs command to create a file
system on that device. See lofiadm(1M) for examples of
creating a UFS and a PC (FAT) file system on a device
created by lofiadm.
Both the block and character devices, such as devices in
/dev/dsk and /dev/rdsk, must be available prior to running
the mkfs command.
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