FFS(5)

NAME
ffs, ufs - Berkeley fast file system

SYNOPSIS
In the kernel configuration file:
options FFS
options QUOTA
options SOFTUPDATES
options SUIDDIR
options UFS_DIRHASH

In fstab(5):
    /dev/disk0a	/mnt ufs rw 1 1

DESCRIPTION
The Berkeley fast file system provides facilities to store file system data onto a disk device. ffs has been optimized over the years for speed and reliability and is the default DragonFly file system for /boot.

  Quotas

options QUOTA
    This option allows system administrators to set limits on disk usage on a per-user basis. Quotas can be used only on file systems mounted with the quota option; see quota(1) and edquota(8).

  Soft Updates

options SOFTUPDATES
    The soft updates feature tracks writes to the disk and enforces metadata update dependencies (e.g., updating free block maps) to ensure that the file system remains consistent.

    To enable soft updates on an unmounted file system, use the following command:

        tunefs -n enable fs

    fs can be either a mount point listed in fstab(5) (e.g., /usr), or a disk device (e.g., /dev/da0s0a).

  File Ownership Inheritance

options SUIDDIR
    For use in file sharing environments on networks including Microsoft Windows and Apple Macintosh computers, this option allows files on file systems mounted with the suiddir option to inherit the ownership of its directory, i.e., “if it's my directory, it must be my file.”

  Directory Hashing

options UFS_DIRHASH
    Implements a hash-based lookup scheme for directories in order to speed up accesses to very large directories.

SYSCTL VARIABLES
The following sysctl(8) MIBs are defined for use with ffs:

vfs.ffs.doasyncfree
    Asynchronously write out modified i-node and indirect blocks upon reallocating file system blocks to be contiguous. (Default: 1.)

vfs.ffs.doreallocblks
    Enable support for the rearrangement of blocks to be contiguous. (Default: 1.)

vfs.ufs.dirhash_docheck
    Enable extra sanity tests. (Default: 0.)

vfs.ufs.dirhash_mem
    Current dirhash memory usage.

vfs.ufs.dirhash_maxmem
    Maximum allowed dirhash memory usage.

vfs.ufs.dirhash_minsize
    Minimum directory size in bytes for which to use hashed lookup.

SEE ALSO
quota(1), edquota(8), sysctl(8) M. McKusick, W. Joy, S. Leffler, R. Fabry, August 1984, A Fast File System for UNIX, ACM Transactions on Computer Systems, 2, 3, 181-197. M. McKusick, June 2000, Soft Updates: A Technique for Eliminating Most Synchronous Writes in the Fast Filesystem, Proceedings of the Freenix Track at the 1999 Usenix Annual Technical Conference, 71-84.