'\" te
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.\" Copyright 1989 AT&T
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.TH UFS 7FS "Jun 18, 2009"
.SH NAME
ufs \- UFS file system
.SH SYNOPSIS
.LP
.nf
\fB#include <sys/param.h>\fR
.fi

.LP
.nf
\fB#include <sys/types.h>\fR
.fi

.LP
.nf
\fB#include <sys/fs/ufs_fs.h>\fR
.fi

.LP
.nf
\fB#include <sys/fs/ufs_inode.h>\fR
.fi

.SH DESCRIPTION
.sp
.LP
\fBUFS\fR is the default disk-based file system for the Solaris environment.
The UFS file system is hierarchical, starting with its root directory (\fB/\fR)
and continuing downward through a number of directories. The root of a UFS file
system is \fBinode 2\fR. A UFS file system's root contents replace the contents
of the directory upon which it is mounted.
.sp
.LP
Subsequent sections of this manpage provide details of the UFS file systems.
.SS "State Flags (\fBfs_state\fR and \fBfs_clean\fR)"
.sp
.LP
UFS uses state flags to identify the state of the file system. \fBfs_state\fR
is \fBFSOKAY\fR - \fBfs_time\fR.  \fBfs_time\fR is the timestamp that indicates
when the last system write occurred. \fBfs_state\fR is updated whenever
\fBfs_clean\fR changes. Some \fBfs_clean\fR values are:
.sp
.ne 2
.na
\fB\fBFSCLEAN\fR\fR
.ad
.RS 12n
Indicates an undamaged, cleanly unmounted file system.
.RE

.sp
.ne 2
.na
\fB\fBFSACTIVE\fR\fR
.ad
.RS 12n
Indicates a mounted file system that has modified data in memory. A mounted
file system with this state flag indicates that user data or metadata would be
lost if power to the system is interrupted.
.RE

.sp
.ne 2
.na
\fB\fBFSSTABLE\fR\fR
.ad
.RS 12n
Indicates an idle mounted file system. A mounted file system with this state
flag indicates that neither user data nor metadata would be lost if power to
the system is interrupted.
.RE

.sp
.ne 2
.na
\fB\fBFSBAD\fR\fR
.ad
.RS 12n
Indicates that this file system contains inconsistent file system data.
.RE

.sp
.ne 2
.na
\fBFSLOG\fR
.ad
.RS 12n
Indicates that the file system has logging enabled. A file system with this
flag set is either mounted or unmounted. If a file system has logging enabled,
the only flags that it can have are \fBFSLOG\fR or \fBFSBAD\fR. A non-logging
file system can have \fBFSACTIVE\fR, \fBFSSTABLE\fR, or \fBFSCLEAN\fR.
.RE

.sp
.LP
It is not necessary to run the \fBfsck\fR command on unmounted file systems
with a state of \fBFSCLEAN\fR, \fBFSSTABLE\fR, or \fBFSLOG\fR. \fBmount\fR(2)
returns \fBENOSPC\fR if an attempt is made to mount a \fBUFS\fR file system
with a state of \fBFSACTIVE\fR for read/write access.
.sp
.LP
As an additional safeguard, \fBfs_clean\fR should be trusted only if
\fBfs_state\fR contains a value equal to \fBFSOKAY\fR - \fBfs_time\fR, where
\fBFSOKAY\fR is a constant integer defined in the
\fB/usr/include/sys/fs/ufs_fs.h\fR file.  Otherwise, \fBfs_clean\fR is treated
as though it contains the value of \fBFSACTIVE\fR.
.SS "Extended Fundamental Types  (\fBEFT\fR)"
.sp
.LP
Extended Fundamental Types (EFT) provide 32-bit user ID (UID), group ID (GID),
and device numbers.
.sp
.LP
If a UID or GID contains an extended value, the short variable (\fBic_suid\fR,
\fBic_sgid\fR) contains the value 65535 and the corresponding UID or GID is in
\fBic_uid\fR or \fBic_gid\fR. Because numbers for block and character devices
are stored in the first direct block pointer of the inode (\fBic_db[0]\fR) and
the disk block addresses are already 32 bit values, no special encoding exists
for device numbers (unlike UID or GID fields).
.SS "Multiterabyte File System"
.sp
.LP
A multiterabyte file system enables creation of a UFS file system up to
approximately 16 terabytes of usable space, minus approximately one percent
overhead. A sparse file can have a logical size of one terabyte. However, the
actual amount of data that can be stored in a file is approximately one percent
less than one terabyte because of file system overhead.
.sp
.LP
On-disk format changes for a multiterabyte UFS file system include:
.RS +4
.TP
.ie t \(bu
.el o
The magic number in the superblock changes from \fBFS_MAGIC\fR to
\fBMTB_UFS_MAGIC\fR. For more information, see the
\fB/usr/include/sys/fs/ufs_fs\fR file.
.RE
.RS +4
.TP
.ie t \(bu
.el o
The \fBfs_logbno\fR unit is a sector for UFS that is less than 1 terabyte in
size and fragments for a multiterabyte UFS file system.
.RE
.SS "UFS Logging"
.sp
.LP
UFS logging bundles the multiple metadata changes that comprise a complete UFS
operation into a transaction. Sets of transactions are recorded in an on-disk
log and are applied to the actual UFS file system's metadata.
.sp
.LP
UFS logging provides two advantages:
.RS +4
.TP
1.
A file system that is consistent with the transaction log eliminates the
need to run \fBfsck\fR after a system crash or an unclean shutdown.
.RE
.RS +4
.TP
2.
UFS logging often provides a significant performance improvement. This is
because a file system with logging enabled converts multiple updates to the
same data into single updates, thereby reducing the number of overhead disk
operations.
.RE
.sp
.LP
The UFS log is allocated from free blocks on the file system and is sized at
approximately 1 Mbyte per 1 Gbyte of file system, up to 256 Mbytes. The log
size may be larger (up to a maximum of 512 Mbytes), depending upon the number
of cylinder groups present in the file system. The log is continually flushed
as it fills up. The log is also flushed when the file system is unmounted or as
a result of a \fBlockfs\fR(1M) command.
.SS "Mounting UFS File Systems"
.sp
.LP
You can mount a UFS file system in various ways using syntax similar to the
following:
.RS +4
.TP
1.
Use \fBmount\fR from the command line:
.sp
.in +2
.nf
# mount -F ufs /dev/dsk/c0t0d0s7 /export/home
.fi
.in -2
.sp

.RE
.RS +4
.TP
2.
Include an entry in the \fB/etc/vfstab\fR file to mount the file system at
boot time:
.sp
.in +2
.nf
/dev/dsk/c0t0d0s7 /dev/rdsk/c0t0d0s7 /export/home  ufs   2   yes  -
.fi
.in -2
.sp

.RE
.sp
.LP
For more information on mounting UFS file systems, see \fBmount_ufs\fR(1M).
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for a description of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Uncommitted
.TE

.SH SEE ALSO
.sp
.LP
\fBdf\fR(1M), \fBfsck\fR(1M), \fBfsck_ufs\fR(1M), \fBfstyp\fR(1M),
\fBlockfs\fR(1M), \fBmkfs_ufs\fR(1M), \fBnewfs\fR(1M), \fBufsdump\fR(1M),
\fBufsrestore\fR(1M), \fBtunefs\fR(1M), \fBmount\fR(2), \fBattributes\fR(5)
.sp
.LP
\fIWriting Device Drivers\fR
.SH NOTES
.sp
.LP
For information about internal UFS structures, see \fBnewfs\fR(1M) and
\fBmkfs_ufs\fR(1M). For information about the \fBufsdump\fR and
\fBufsrestore\fR commands, see \fBufsdump\fR(1M), \fBufsrestore\fR(1M), and
\fB/usr/include/protocols/dumprestore.h\fR.
.sp
.LP
If you experience difficulty in allocating space on the ufs filesystem, it may
be due to framentation. Fragmentation can occur when you do not have sufficient
free blocks to satisfy an allocation request even though \fBdf\fR(1M) indicates
that enough free space is available. (This may occur because df only uses the
available fragment count to calculate available space, but the file system
requires contiguous sets of fragments for most allocations). If you suspect
that you have exhausted contiguous  fragments on  your file system, you can use
the \fBfstyp\fR(1M) utility with the -v option. In the \fBfstyp\fR output,
look at the  \fInbfree\fR (number  of  blocks  free) and \fInffree\fR (number
of fragments free) fields. On unmounted filesystems, you can use \fBfsck\fR(1M)
and observe  the  last line of output, which reports, among other items, the
number of fragments and the degree of fragmentation. To correct a fragmentation
problem, run \fBufsdump\fR(1M) and \fBufsrestore\fR(1M) on the ufs filesystem.