freebsd-nq/share/man/man7/ffs.7

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.\" This software was developed for the FreeBSD Project by Chris
.\" Costello at Safeport Network Services and NAI Labs, the Security
.\" Research Division of Network Associates, Inc. under DARPA/SPAWAR
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.\" $FreeBSD$
.Dd December 26, 2001
.Dt FFS 4
.Sh NAME
.Nm ffs
.Nd Berkeley fast file system
.Sh SYNOPSIS
In the kernel configuration file:
.Cd options ENABLE_VFS_IOOPT
.Cd options FFS
.Cd options QUOTA
.Cd options SOFTUPDATES
.Cd options SUIDDIR
.Cd options UFS_ACL
.Cd options UFS_DIRHASH
.Cd options UFS_EXTATTR
.Cd options UFS_EXTATTR_AUTOSTART
.Pp
In
.Pa /etc/fstab :
.Cd /dev/disk0s1a	/mnt ufs rw 1 1
.Sh DESCRIPTION
The Berkeley fast file system
provides facilities to store file system data onto a disk device.
.Nm ffs
has been optimized over the years
for speed and reliability
and is the default
.Fx
file system.
.Pp
.Ss VFS I/O optimization
.Bl -tag -width 2n
.It Cd options ENABLE_VFS_IOOPT
This option enables the IO optimization through the VM system,
using VM operations instead of copying operations when possible.
This option adds a sysctl MIB,
.Em vfs.ioopt .
The following are values and effects for
.Em vfs.ioopt :
.Pp
.Bl -tag -width "Value" -offset indent -compact
.It Em Value
.Em Effect
.It Li 0
No optimization
.It Li 1
VM operations if a request fits
.It Li 2
Aggresive optimization (VM used as much as possible)
.El
.El
.Ss Quotas
.Bl -tag -width 2n
.It 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
.Sq quota
option;
see
.Xr quota 1
and
.Xr edquota 8 .
.El
.Ss Soft Updates
.Bl -tag -width 2n
.It Cd options SOFTUPDATES
The soft updates feature tracks writes to the disk
and enforces metadata update dependancies
(e.g. updating free block maps)
to ensure that the file system remains consistent.
.Pp
To enable soft updates on an
.Em unmounted
file system, use the following command:
.Pp
.Dl Ic tunefs -n enable Sy /foo
.Pp
.Dq Sy foo
can be either a mount point listed in
.Pa /etc/fstab
(e.g.
.Pa /usr ) ,
or a disk device
(e.g.
.Pa /dev/da0s1a ) .
.El
.Ss File Ownership Inheritance
.Bl -tag -width 2n
.It 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
.Sq suiddir
option
to inherit the ownership of its directory,
i.e.
.Dq "If it's my directory, it must be my file."
.El
.Ss Access Control Lists
.Bl -tag -width 2n
.It Cd options UFS_ACL
Access control lists allow the association of
fine-grained descretionary access control information
with files and directories.
This option requires the presence of the
.Dv UFS_EXTATTR
option, and it is recommended that
.Dv UFS_EXTATTR_AUTOSTART
is included as well,
so that ACLs are enabled atomically upon mounting the file system.
.El
.Pp
In order to enable support for ACLs,
two extended attributes must be available in the
.Dv EXTATTR_NAMESPACE_SYSTEM
namespace:
.Dq Li posix1e.acl_access ,
which holds the access ACL,
and
.Dq Li 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.
.Pp
.Bd -literal -offset indent
mkdir -p /.attribute/system
cd /.attribute/system
extattrctl initattr -p / 388 posix1e.acl_access
extattrctl initattr -p / 388 posix1e.acl_default
.Ed
.Pp
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.
.Ss Directory Hashing
.Bl -tag -width 2n
.It Cd options UFS_DIRHASH
Implements a hash-based lookup scheme for directories
in order to speed up accesses to very large directories.
.El
.Ss Extended Attributes
.Bl -tag -width 2n
.It 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
.Xr extattrctl 8 .
.It Cd options UFS_EXTATTR_AUTOSTART
If this option is defined,
.Nm ffs
will search for a
.Dq Pa .attribute
subdirectory of the file system root during the mount operation.
If found, extended attribute support will be
automatically started for that file system.
.El
.Pp
The following
.Xr sysctl 8
MIBs are defined for use with
.Nm ffs :
.Bl -hang -width "vfs.ffs.doreallocblk" 
.It Em vfs.ffs.doasyncfree
Asynchronously write out modified inode and indirect blocks
upon reallocating file system blocks to be contiguous.
(Default: 1.)
.It Em vfs.ffs.doreallocblks
Enable support for the rearrangement of blocks
to be contiguous.
(Default: 1.)
.El
.Sh SEE ALSO
.Xr quota 1 ,
.Xr acl 3 ,
.Xr extattr 3 ,
.Xr edquota 8 ,
.Xr extattrctl 8 ,
.Xr sysctl 8 ,
.Rs
.%A M. McKusick
.%A W. Joy
.%A S. Lefler
.%A R. Fabry
.%D August 1984
.%T "A Fast File System for UNIX"
.%J "ACM Transactions on Computer Systems"
.%N 2
.%V 3
.%P 181-197
.Re
.Rs
.%A M. McKusick
.%D June 2000
.%T "Soft Updates: A Technique for Eliminating Most Synchronous Writes in the Fast Filesystem"
.%J "Proceedings of the Freenix Track at the 1999 Usenix Annual Technical Conference"
.%P 71-84
.Re