mkfs_ufs(1M)

Synopsis

mkfs [-F ufs] [generic_options] [-o specific_options] special size

Description

mkfs constructs a file system by writing on the special file special unless the `-o N' flag has been specified. The numeric size specifies the number of logical 512 byte sectors in the file system. mkfs builds a file system with a root directory and a lost+found directory (see fsck(1M)).

The options are:

-F ufs

Specifies the ufs-FSType.

-o

Specify ufs file system-specific options. These options can be specified in any order, but must be separated by commas. The following options are available:

N

Do not write the file system to the special file. This suboption gives all the information needed to create a file system but 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 (the default) or 8192.

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 8192. The default is 1024.

cgsize=n

The number of disk cylinders per cylinder group. n must be in the range 1 to 32. cgsize has different defaults, depending on the size of the cylinder group. If the cylinder group is less than 3/4 MB, cgsize defaults to 16. If the cylinder group is between 3/4 and 1.5 MB, cgsize defaults to 12. If the cylinder group is greater than 1.5 MB, cgsize defaults to 8.

nbpi=n

The number of bytes for which one inode block is allocated. The default currently set at one inode block for every 2048 bytes.

free=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%. It is inadvisable to reduce the allocation of free space below the default level because this may adversely affect performance. free also determines when a filesystem will automatically switch between time optimization and space optimization.

rps=n

The rotational speed of the disk, in revolutions per second. The default is 60.

opt=s|t

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 (SCSI devices only). 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 successive blocks in a file. The default is 4.

C

Some applications that pre-date SVR4 do not work on file systems with more than 64K inodes. Therefore, when the number of inodes for the file system being built exceeds the 64K limit, mkfs prompts the user to confirm that he or she indeed wants the large number of inodes. The -o C option silences this mkfs prompt and limits the number of inodes to a maximum of 64K, ensuring perfect binary compatibility with the pre-Release 4 UNIX System.

L

When the number of inodes for the file system being built exceeds the 64K limit, mkfs prompts the user to confirm that he or she indeed wants the large number of inodes. The -o L option silences this prompt and allows the user to create a file system with more than 64K inodes.

special

mkfs constructs a file system by writing on the special file.

size

Specify the number of logical 512 byte sectors in the file system. The largest file system size is a maximum of 4,194,304 512-byte sectors (2 gigabytes).

Notices

You should keep a note of spare superblock copies in the ufs file system, so that in the event of superblock corruption, you will know which blocks contain spare entries.

References