NAME
ffs
—
Berkeley fast file system
SYNOPSIS
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
options UFS_GJOURNAL
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 FreeBSD
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 create a new file system with the soft updates enabled, use newfs(8) command:
newfs
-U
fsfs can be either a mount point listed in fstab(5) (e.g., /usr), or a disk device (e.g., /dev/da0a).
It is possible to enable soft updates on an unmounted file system by using tunefs(8) command:
tunefs
-n
enable
fsSoft updates can also add journaling that reduces the time spent by fsck_ffs(8) cleaning up a filesystem after a crash from several minutes to a few seconds. The journal is placed in an inode named .sujournal, and is kept as a circular log of segments containing records that describe metadata operations.
To create a new file system with both the soft updates and soft updates journaling enabled, use the following command:
newfs
-j
fsThis runs tunefs(8) command after newfs(8) command with
-U
flag enabled. It is possible to enable soft updates journaling on an unmounted file system by using tunefs(8) command:tunefs
-j
enable
fsThis flag automatically enables the soft updates feature when it is not enabled. Note that this tunefs(8) command will fail if a file .sujournal already exists before enabling the soft updates journaling.
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 thatUFS_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
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,
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.
GEOM-based Journaling
options UFS_GJOURNAL
- Implements a block level journaling of a UFS file system, which is for
both data and metadata. To enable this, create a
gjournal(8) GEOM provider for a block device by using the
following command:
gjournal label
da0In this example, /dev/da0 is used as the target block device, and /dev/da0.journal is created. Then create a new file system by using newfs(8) with the block level journaling flag and mount it:
newfs
-J
/dev/da0.journalmount
-o
async
/dev/da0.journal /mntasync
option is not mandatory but recommended for better performance because the journaling guarantees the consistency of anasync
mount.It is also possible to enable the block level journaling on an existing file system. To do so, use gjournal(8) utility to label the underlying block device and tunefs(8) utility to enable the block level journaling flag:
gjournal label
da0tunefs
-J
enable
/dev/da0.journalmount
-o
async
/dev/da0.journal /mnt
sysctl(8) MIBs
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).
HISTORY
The ffs
manual page first appeared in
FreeBSD 4.5.
SEE ALSO
quota(1), acl(3), extattr(3), edquota(8), extattrctl(8), fsck_ffs(8), sysctl(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, 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.
M. McKusick and J. Roberson, Journaled Soft-updates, BSD Canada Conference 2010 (BSDCan), May 2010.