path: root/share/man/man7/ffs.7

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.Dd December 26, 2001
.Dt FFS 7
.Sh NAME
.Nm ffs
.Nd Berkeley fast filesystem
.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
.Xr fstab 5 :
.Bd -literal -compact
/dev/disk0a	/mnt ufs rw 1 1
.Ed
.Sh DESCRIPTION
The Berkeley fast filesystem
provides facilities to store filesystem data onto a disk device.
.Nm
has been optimized over the years
for speed and reliability
and is the default
.Fx
filesystem.
.Ss VFS I/O optimization
.Bl -tag -width 2n
.It Cd "options ENABLE_VFS_IOOPT"
This option enables the I/O optimization through the VM system,
using VM operations instead of copying operations when possible.
This option adds a
.Xr sysctl 8
MIB,
.Va vfs.ioopt .
The following are values and effects for
.Va vfs.ioopt :
.Pp
.Bl -tag -width ".Em 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
Aggressive 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 filesystems
mounted with the
.Cm 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 dependencies
(e.g., updating free block maps)
to ensure that the filesystem remains consistent.
.Pp
To enable soft updates on an
.Em unmounted
filesystem, use the following command:
.Pp
.D1 Nm tunefs Fl n Cm enable Ar fs
.Pp
.Ar fs
can be either a mount point listed in
.Xr fstab 5
(e.g.,
.Pa /usr ) ,
or a disk device
(e.g.,
.Pa /dev/da0a ) .
.El
.Ss File Ownership Inheritance
.Bl -tag -width 2n
.It Cd "options SUIDDIR"
For use in file sharing environments
on networks including
.Tn "Microsoft Windows"
and
.Tn "Apple Macintosh"
computers,
this option allows files on filesystems
mounted with the
.Cm 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 discretionary 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 filesystem.
.El
.Pp
In order to enable support for ACLs,
two extended attributes must be available in the
.Dv EXTATTR_NAMESPACE_SYSTEM
namespace:
.Pa posix1e.acl_access ,
which holds the access ACL,
and
.Pa posix1e.acl_default ,
which holds the default ACL for directories.
If you are using filesystem 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 filesystem.
In these examples, the root filesystem is used;
see
.Sx "Extended Attributes"
for more details.
.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 filesystem,
the attributes will be automatically started
(if
.Dv 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
will search for a
.Pa .attribute
subdirectory of the filesystem root during the mount operation.
If found, extended attribute support will be
automatically started for that filesystem.
.El
.Pp
The following
.Xr sysctl 8
MIBs are defined for use with
.Nm :
.Bl -hang -width ".Va vfs.ffs.doreallocblk"
.It Va vfs.ffs.doasyncfree
Asynchronously write out modified i-node and indirect blocks
upon reallocating filesystem blocks to be contiguous.
(Default: 1.)
.It Va 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