The Berkeley fast file system
provides facilities to store file system data onto a disk device.
has been optimized over the years
for speed and reliability
and is the default
Fx 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
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:
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
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
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
Sx Extended Attributes
for more details.
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
options UFS_DIRHASH
Implements a hash-based lookup scheme for directories
in order to speed up accesses to very large directories.
Extended Attributes
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).
options UFS_EXTATTR_AUTOSTART
If this option is defined,
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
:
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.)
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
