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MKFS(8)                     System Manager's Manual                    MKFS(8)



NAME
       mkfs - construct a file system

SYNOPSIS
       /usr/etc/mkfs [ -N ] special size [ nsect ] [ ntrack ]
            [ blksize ] [ fragsize ] [ ncpg ] [ minfree ]
            [ rps ] [ nbpi ] [ opt ] [ apc ] [ rot ] [ nrpos ] [ maxcontig ]

DESCRIPTION
       Note: file systems are normally created with the newfs(8) command.

       mkfs  constructs  a  file system by writing on the special file special
       unless the -N flag has been specified.  special must be specified as  a
       raw device and disk partition.  For example, to create a file system on
       sd0, specify /dev/rsd0[a-h], where a-h is the disk partition.

       The numeric size specifies the number of sectors in  the  file  system.
       mkfs builds a file system with a root directory and a lost+found direc-
       tory (see fsck(8)).  The number of inodes is calculated as  a  function
       of  the  file system size.  No boot program is initialized by mkfs (see
       newfs(8)).

       You must be super-user to use this command.

OPTIONS
       -N     Print out the file system parameters without  actually  creating
              the file system.

       The  following arguments allow fine tune control over the parameters of
       the file system.

       nsect  The number of sectors per track on the disk.  The default is 32.

       ntrack The number of tracks per cylinder on the disk.  The  default  is
              16.

       blksize
              The primary block size for files on the file system.  It must be
              a power of two,  currently  selected  from  4096  or  8192  (the
              default).

       fragsize
              The  fragment  size  for files on the file system.  The fragsize
              represents the smallest amount of disk space that will be  allo-
              cated  to  a file.  It must be a power of two currently selected
              from the range 512 to 8192.  The default is 1024.

       ncpg   The number of disk cylinders per cylinder group.  The default is
              16.

       minfree
              The  minimum  percentage  of  free disk space allowed.  Once the
              file system capacity reaches this threshold, only the super-user
              is allowed to allocate disk blocks.  The default value is 10%.

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

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

       opt    Space or time optimization preference; s specifies  optimization
              for space, t specifies optimization for time.  The default is t.

       apc    The  number of alternates per cylinder (SCSI devices only).  The
              default is 0.

       rot    The expected time (in milliseconds) to service a  transfer  com-
              pletion  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 1.

              Note:  in  earlier  releases  mkfs tried to guess what the right
              value for this parameter by querying the controller type.  Since
              mkfs  is  a  more primitive interface, this query has been moved
              into newfs.  mkfs now does exactly what you tell it to do.

       nrpos  The number of distinguished rotational positions.   The  default
              is 8.

       maxcontig
              The maximum number of blocks that will be allocated contiguously
              before inserting a rotational delay.  The default is 1.

              Note: 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(8).

       Users  with  special demands for their file systems are referred to the
       paper cited below for a discussion of the tradeoffs in using  different
       configurations.

SEE ALSO
       dir(5), fs(5), fsck(8), newfs(8), tunefs(8)

       McKusick, Joy, Leffler; A Fast File System for UNIX

NOTES
       newfs(8) is preferred for most routine uses.



                                  5 July 1990                          MKFS(8)