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.
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
quotaoption; 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-nenablefsfs 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
suiddiroption 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, and R. Fabry, A Fast File System for UNIX, ACM Transactions on Computer Systems, 2, 3, 181-197, August 1984.
M. McKusick, 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, June 2000.