MKFS_UFS(8) Maintenance Commands and Procedures MKFS_UFS(8)

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(8)).


The UFS-specific mkfs is rarely run directly. Use the newfs(8)
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 system, 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(8) 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.


calcbinsb
Sends to stdout a binary (machine-readable)
version of the superblock that would be used to
create a file system with the specified
configuration parameters.


calcsb
Sends to stdout a human-readable version of the
superblock that would be used to create a file
system with the specified configuration
parameters.


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 multiplied 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 continue
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(8) command.


gap=n
Rotational delay. This option is obsolete in the
Solaris 10 release. 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 calculated from kernel parameters as follows:

If maxphys is less than ufs_maxmaxphys, which is
typically 1 Mbyte, then maxcontig is set to
maxphys. Otherwise, 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(8).


mtb=y
Set the parameters of the file system to allow
eventual 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 creating 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(8) 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.

SEE ALSO

ufs(4FS), dir_ufs(5), attributes(7), fsck(8), mkfs(8), newfs(8),
tunefs(8)

DIAGNOSTICS

The following error message typically occurs with very high density
disks. On such disks, the file system structure cannot 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 performance. 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


If there is only one cylinder group and if the above condition holds
true, mkfs fails with the following error:

File system creation failed. There is only one cylinder group and that is
not even big enough to hold the inodes.


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(8) 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.

March 8, 2006 MKFS_UFS(8)