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download PDF document: ffs.7.pdf

FFS(7) FreeBSD Miscellaneous Information Manual FFS(7)
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 fs
fs 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 fs
Soft 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:

This 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 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 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 /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.journal mount -o async /dev/da0.journal /mnt
async option is not mandatory but recommended for better performance because the journaling guarantees the consistency of an async 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 da0 tunefs -J enable /dev/da0.journal mount -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.
FreeBSD 14.0-RELEASE-p11 May 3, 2020 FreeBSD 14.0-RELEASE-p11