Commands for Creating a Customized File System

/usr/sbin/newfs [-Nv] [mkfs_options] raw_device

-N

Displays the file system parameters that would be used in creating the file system without actually creating it. This option does not display the parameters that were used to create an existing file system. 

-T

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 use the -f or -i options to specify a fragsize or nbpi that is incompatible with this option, the user-supplied value of fragsize or nbpi is ignored.

-v

Displays the parameters that are passed to the mkfs command.

mkfs-options

Use the options in this table, from -s size to -C maxcontig, to set the mkfs parameters. The options are listed in the order they are passed to the mkfs command. Separate the options with spaces.

-s size

The size of the file system in sectors. The default is to use the entire partition. 

-t ntrack

The number of tracks per cylinder on the disk. The default is determined from the disk label. 

-b bsize

The logical block size of the file system, which is either 4096 or 8192 bytes. The default is 8192 bytes. The sun4u architecture does not support the 4096 block size. 

-f fragsize

The smallest amount of disk space in bytes that is allocated to a file. When 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 for fragsize 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 -T option, fragsize is forced to match block size (bsize).

-c cgsize

The number of disk cylinders per cylinder group, which ranges from 16 to 256. The default value is calculated by dividing the number of sectors in the file system by the number of sectors in 1 Gbyte, and then multiplying the result by 32. The default value is always between 16 to 256. 

Use the mkfs command to override the default value.

This option is not applicable for disks with EFI labels and is ignored. 

-m free

The minimum percentage of free disk space to maintain in the file system (between 1% and 99%, inclusively). This space is off limits to regular 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 modified after the file system is created by using the tunefs command.

-r rpm

The speed of the disk, in revolutions per minute. This setting is driver- or device-specific. 

This parameter is converted to revolutions per second before it is passed to the mkfs command.

This option is not applicable for disks with EFI labels and is ignored. 

-i nbpi

The number of bytes per inode to use in computing how many inodes to create for the file system. For the default values, see Number of Inodes (Files).

-o opt

Optimization type to use for allocating disk blocks to files: space or time. The default is time.

-a apc

The number of alternate sectors per disk cylinder to reserve for bad block placement for SCSI devices only. The default is 0. 

This option is not applicable for disks with EFI labels and is ignored. 

-d gap

Rotational delay. The expected minimum number of milliseconds it takes the CPU to complete a data transfer and initiate a new data transfer on the same disk cylinder. The default is 0.  

-n nrpos

The number of different rotation 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. 

-C maxcontig

The maximum number of blocks, belonging to one file, that will be allocated contiguously before inserting a rotational delay. The default varies from drive to drive. Drives without internal (track) buffers (or drives or controllers that don't advertise the existence of an internal buffer) default to 1. Drives with buffers default to 7. 

This parameter is limited in the following way: 

blocksize x maxcontig must be <= maxphys

maxphys is a read-only kernel variable that specifies the maximum block transfer size (in bytes) that the I/O subsystem is capable of satisfying. This limit is enforced by the mount command, not by newfs or mkfs command.

This parameter also controls clustering. Regardless of the value of rotdelay, clustering is enabled only when maxcontig is greater than 1. Clustering allows higher I/O rates for sequential I/O and is described in tunefs(1M).

raw_device

The special character (raw) device file name of the partition that will contain the file system. This argument is required. 

# newfs -N /dev/rdsk/c0t0d0s0
/dev/rdsk/c0t0d0s0:  37260 sectors in 115 cylinders of 9 tracks, 36 sectors
        19.1MB in 8 cyl groups (16 c/g, 2.65MB/g, 1216 i/g)
superblock backups (for fsck -b #) at:
 32, 5264, 10496, 15728, 20960, 26192, 31424, 36656,
#