NEWFS(8)                OpenBSD System Manager's Manual               NEWFS(8)

NAME
     newfs, mount_mfs - construct a new file system

SYNOPSIS
     newfs [-NO] [-S sector-size] [-a maxcontig] [-b block-size] [-c
           cylinders] [-d rotdelay] [-e maxbpg] [-f frag-size] [-i bytes] [-k
           skew] [-l interleave] [-m free space] [-n nrpos] [-o optimization]
           [-p sectors] [-q] [-r revolutions] [-s size] [-t fstype] [-u
           sectors] [-x sectors] [-z tracks] special

     mount_mfs [-N] [-a maxcontig] [-b block-size] [-c cylinders] [-d
           rotdelay] [-e maxbpg] [-f frag-size] [-i bytes] [-m free space] [-o
           options] [-s size] special node

DESCRIPTION
     Before running newfs or mount_mfs, the disk must be labeled using
     disklabel(8). newfs builds a file system on the specified special device,
     basing its defaults on the information in the disk label.  Typically the
     defaults are reasonable, although newfs has numerous options to allow the
     defaults to be selectively overridden.

     mount_mfs is used to build a file system in virtual memory and then mount
     it on a specified node.  mount_mfs exits and the contents of the file
     system are lost when the file system is unmounted.  If mount_mfs is sent
     a signal while running, for example during system shutdown, it will at-
     tempt to unmount its corresponding file system.  The parameters to
     mount_mfs are the same as those to newfs. The special file is only used
     to read the disk label which provides a set of configuration parameters
     for the memory based file system.  The special file is typically that of
     the primary swap area, since that is where the file system will be backed
     up when free memory gets low and the memory supporting the file system
     has to be paged.  If the keyword ``swap'' is used instead of a special
     file name, default configuration parameters will be used.  (This option
     is useful when trying to use mount_mfs on a machine without any disks.)

     Both newfs and mount_mfs now have the functionality of fsirand(8) built-
     in so it is not necessary to run fsirand(8) manually unless you wish to
     re-randomize the filesystem (or list the inode generation numbers).

     The following options define the general layout policies:

     -N          Causes the file system parameters to be printed out without
                 really creating the file system.

     -O          Creates a 4.3BSD format filesystem.  This options is primari-
                 ly used to build root filesystems that can be understood by
                 older boot ROMs.

     -q          Operate in quiet mode.  With this option, newfs will not
                 print extraneous information like superblock backups.

     -a maxcontig
                 This specifies the maximum number of contiguous blocks that
                 will be laid out before forcing a rotational delay (see the
                 -d option).  The default value is 8.  See tunefs(8) for more
                 details on how to set this option.

     -b block-size
                 The block size of the file system, in bytes.

     -c #cylinders/group
                 The number of cylinders per cylinder group in a file system.

                 The default value is 16.

     -d rotdelay
                 This specifies the expected time (in milliseconds) to service
                 a transfer completion interrupt and initiate a new transfer
                 on the same disk.  The default is 0 milliseconds.  See
                 tunefs(8) for more details on how to set this option.

     -e maxbpg   This indicates the maximum number of blocks any single file
                 can allocate out of a cylinder group before it is forced to
                 begin allocating blocks from another cylinder group.  The de-
                 fault is about one quarter of the total blocks in a cylinder
                 group.  See tunefs(8) for more details on how to set this op-
                 tion.

     -f frag-size
                 The fragment size of the file system in bytes.

     -i number of bytes per inode
                 This specifies the density of inodes in the file system.  The
                 default is to create an inode for each 4096 bytes of data
                 space.  If fewer inodes are desired, a larger number should
                 be used; to create more inodes a smaller number should be
                 given.

     -m free space %
                 The percentage of space reserved from normal users; the mini-
                 mum free space threshold.  The default value used is 5%.  See
                 tunefs(8) for more details on how to set this option.

     -n number of rotational positions
                 The number of distinct rotational positions.  The default is
                 1.

     -o optimization preference
                 space or time. 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.  Unless an
                 optimization has been specified, if the value of minfree (see
                 above) is less than 5%, the default is to optimize for space;
                 if the value of minfree is greater than or equal to 5%, the
                 default is to optimize for time.  See tunefs(8) for more de-
                 tails on how to set this option.

     -s size     The size of the file system in sectors.

     The following options override the standard sizes for the disk geometry.
     Their default values are taken from the disk label.  Changing these de-
     faults is useful only when using newfs to build a file system whose raw
     image will eventually be used on a different type of disk than the one on
     which it is initially created (for example on a write-once disk).  Note
     that changing any of these values from their defaults will make it impos-
     sible for fsck(8) to find the alternate superblocks if the standard su-
     perblock is lost.

     -S sector-size
                 The size of a sector in bytes (almost never anything but
                 512).

     -k sector 0 skew, per track
                 Used to describe perturbations in the media format to compen-
                 sate for a slow controller.  Track skew is the offset of sec-
                 tor 0 on track N relative to sector 0 on track N-1 on the
                 same cylinder.

     -l hardware sector interleave
                 Used to describe perturbations in the media format to compen-
                 sate for a slow controller.  Interleave is physical sector
                 interleave on each track, specified as the denominator of the
                 ratio:
                       sectors read/sectors passed over
                 Thus an interleave of 1/1 implies contiguous layout, while
                 1/2 implies logical sector 0 is separated by one sector from
                 logical sector 1.

     -p spare sectors per track
                 Spare sectors (bad sector replacements) are physical sectors
                 that occupy space at the end of each track.  They are not
                 counted as part of the sectors/track (-u) since they are not
                 available to the file system for data allocation.

     -r revolutions/minute
                 The speed of the disk in revolutions per minute.

     -z #tracks/cylinder
                 The number of tracks/cylinder available for data allocation
                 by the file system.

     -t fstype   Set the filesystem type of which filesystem you wish to cre-
                 ate.  newfs will be smart enough to run the alternate
                 newfs_XXX program instead.

     -u sectors/track
                 The number of sectors per track available for data allocation
                 by the file system.  This does not include sectors reserved
                 at the end of each track for bad block replacement (see the
                 -p option).

     -x spare sectors per cylinder
                 Spare sectors (bad sector replacements) are physical sectors
                 that occupy space at the end of the last track in the cylin-
                 der.  They are deducted from the sectors/track (-u) of the
                 last track of each cylinder since they are not available to
                 the file system for data allocation.

     The options to the mount_mfs command are as described for the newfs com-
     mand, except for the -o option.

     That option is as follows:

     -o      Options are specified with a -o flag followed by a comma separat-
             ed string of options.  See the mount(8) man page for possible op-
             tions and their meanings.

SEE ALSO
     disktab(5), fs(5), disklabel(8), dumpfs(8), fsck(8), fsirand(8),
     mount(8), tunefs(8)

     M. McKusick, W. Joy, S. Leffler, and R. Fabry, "A Fast File System for
     UNIX,", ACM Transactions on Computer Systems 2, 3, pp 181-197, August
     1984, (reprinted in the BSD System Manager's Manual).

HISTORY
     The newfs command appeared in 4.2BSD.

OpenBSD 2.9                     March 27, 1994                               3
