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Manual Pages  — FFS


ffs – Berkeley fast file system



In the kernel configuration file: options FFS options QUOTA options SOFTUPDATES options SUIDDIR options UFS_ACL options UFS_DIRHASH options UFS_EXTATTR options UFS_EXTATTR_AUTOSTART

In fstab(5):

/dev/disk0a     /mnt ufs rw 1 1


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 FreeBSD file system.


Cd 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

  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:

fs can be either a mount point listed in fstab(5) (e.g., /usr), or a disk device (e.g., /dev/da0a).

File Ownership Inheritance

Cd 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."

Access Control Lists

Cd options UFS_ACL
  Access control lists allow the association of fine-grained discretionary access control information with files and directories. This option requires the presence of the UFS_EXTATTR option, and it is recommended that UFS_EXTATTR_AUTOSTART is included as well, so that ACLs are enabled atomically upon mounting the file system.

In order to enable support for ACLs, two extended attributes must be available in the EXTATTR_NAMESPACE_SYSTEM namespace: posix1e.acl_access, which holds the access ACL, and posix1e.acl_default, which holds the default ACL for directories. If you are using file system extended attributes, the following commands may be used to allocate space for and create the necessary EA backing files for ACLs in the root of each file system. In these examples, the root file system is used; see Extended Attributes for more details.

mkdir -p /.attribute/system
cd /.attribute/system
extattrctl initattr -p / 388 posix1e.acl_access
extattrctl initattr -p / 388 posix1e.acl_default

On the next mount of the root file system, the attributes will be automatically started (if UFS_EXTATTR_AUTOSTART is included in the kernel configuration), and ACLs will be enabled.

Directory Hashing

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

Extended Attributes

Cd options UFS_EXTATTR
  Extended attributes allow the association of additional arbitrary metadata with files and directories, which can be assigned and retrieved from userland as well as from within the kernel; see extattrctl(8).
  If this option is defined, ffs will search for a .attribute subdirectory of the file system root during the mount operation. If found, extended attribute support will be automatically started for that file system.

The following sysctl(8) MIBs are defined for use with ffs:
  Asynchronously write out modified i-node and indirect blocks upon reallocating file system blocks to be contiguous. (Default: 1.)
  Enable support for the rearrangement of blocks to be contiguous. (Default: 1.)


quota(1), acl(3), extattr(3), edquota(8), extattrctl(8), sysctl(8)

M. McKusick, W. Joy, S. Leffler, R. Fabry, 2, ACM Transactions on Computer Systems, 181-197, A Fast File System for UNIX, 3, August 1984.

M. McKusick, Proceedings of the Freenix Track at the 1999 Usenix Annual Technical Conference, 71-84, Soft Updates: A Technique for Eliminating Most Synchronous Writes in the Fast Filesystem, June 2000.

FFS (7) December 26, 2001

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