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ufs(7FS)							      ufs(7FS)

NAME
       ufs - UFS file system

SYNOPSIS
       #include	<sys/param.h>

       #include	<sys/types.h>

       #include	<sys/fs/ufs_fs.h>

       #include	<sys/fs/ufs_inode.h>

       UFS  is the default disk-based file system for the Solaris environment.
       The UFS file system is hierarchical, starting with its  root  directory
       (/)  and	 continuing downward through a number of directories. The root
       of a UFS	file system is inode 2.	A UFS file system's root contents  re-
       place the contents of the directory upon	which it is mounted.

       Subsequent  sections  of	 this  manpage provide details of the UFS file
       systems.

   State Flags (fs_state and fs_clean)
       UFS uses	state flags to identify	the state of the file system. fs_state
       is  FSOKAY - fs_time.  fs_time is the timestamp that indicates when the
       last system write  occurred.  fs_state  is  updated  whenever  fs_clean
       changes.	Some fs_clean values are:

       FSCLEAN		       Indicates  an undamaged,	cleanly	unmounted file
			       system.

       FSACTIVE		       Indicates a mounted file	system that has	 modi-
			       fied 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.

       FSSTABLE		       Indicates  an  idle  mounted  file  system.   A
			       mounted	file system with this state flag indi-
			       cates that neither user data nor	metadata would
			       be lost if power	to the system is interrupted.

       FSBAD		       Indicates that this file	system contains	incon-
			       sistent file system data.

       FSLOG		       Indicates that the file system has logging  en-
			       abled.  A file system with this flag set	is ei-
			       ther mounted or unmounted. If a file system has
			       logging	enabled,  the  only  flags that	it can
			       have are	FSLOG or FSBAD.	  A  non-logging  file
			       system can have FSACTIVE, FSSTABLE, or FSCLEAN.

       It  is  not necessary to	run the	fsck command on	unmounted file systems
       with a state of FSCLEAN,	FSSTABLE, or FSLOG. mount(2) returns ENOSPC if
       an  attempt is made to mount a UFS file system with a state of FSACTIVE
       for read/write access.

       As an additional	safeguard, fs_clean should be trusted only if fs_state
       contains	 a value equal to FSOKAY - fs_time, where FSOKAY is a constant
       integer defined in the /usr/include/sys/fs/ufs_fs.h  file.   Otherwise,
       fs_clean	is treated as though it	contains the value of FSACTIVE.

   Extended Fundamental	Types  (EFT)
       Extended	Fundamental Types (EFT)	provide	32-bit user ID (UID), group ID
       (GID), and device numbers.

       If a UID	 or  GID  contains  an	extended  value,  the  short  variable
       (ic_suid,  ic_sgid)  contains the value 65535 and the corresponding UID
       or GID is in ic_uid or ic_gid. Because numbers for block	and  character
       devices	are  stored  in	 the  first  direct block pointer of the inode
       (ic_db[0]) and the disk block addresses are already 32 bit  values,  no
       special encoding	exists for device numbers (unlike UID or GID fields).

   Multiterabyte File System
       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 ter-
       abyte. 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.

       On-disk format changes for a multiterabyte UFS file system include:

	 o  The	magic number  in  the  superblock  changes  from  FS_MAGIC  to
	    MTB_UFS_MAGIC.    For   more   information,	  see	the   /usr/in-
	    clude/sys/fs/ufs_fs	file.

	 o  The	fs_logbno unit is a sector for UFS that	is less	 than  1  ter-
	    abyte in size and fragments	for a multiterabyte UFS	file system.

   UFS Logging
       UFS  logging bundles the	multiple metadata changes that comprise	a com-
       plete UFS operation  into  a  transaction.  Sets	 of  transactions  are
       recorded	 in an on-disk log and are applied to the actual UFS file sys-
       tem's metadata.

       UFS logging provides two	advantages:

       1.  A file system that is consistent with the  transaction  log	elimi-
	   nates the need to run fsck after a system crash or an unclean shut-
	   down.

       2.  UFS logging often provides a	significant  performance  improvement.
	   This	 is because a file system with logging enabled converts	multi-
	   ple updates to the same data	into single updates, thereby  reducing
	   the number of overhead disk operations.

       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	a max-
       imum  of	 64 Mbytes. 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 lockfs	command.

   Mounting UFS	File Systems
       You can mount a UFS file	system in various ways using syntax similar to
       the following:

       1.  Use mount from the command line:

	   # mount -F ufs /dev/dsk/c0t0d0s7 /export/home

       2.  Include an entry in the /etc/vfstab file to mount the  file	system
	   at boot time:

	   /dev/dsk/c0t0d0s7 /dev/rdsk/c0t0d0s7	/export/home  ufs   2	yes  -

       For more	information on mounting	UFS file systems, see mount_ufs(1M).

       See attributes(5) for a description of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE	TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Unstable			   |
       +-----------------------------+-----------------------------+

       df(1M),	fsck(1M),  fsck_ufs(1M),  fstyp(1M),  mkfs_ufs(1M), newfs(1M),
       ufsdump(1M), ufsrestore(1M), tunefs(1M),	mount(2), attributes(5)

NOTES
       For information	about  internal	 UFS  structures,  see	newfs(1M)  and
       mkfs_ufs(1M).  For  information	about  the ufsdump and ufsrestore com-
       mands,  see  ufsdump(1M),   ufsrestore(1M),   and   /usr/include/proto-
       cols/dumprestore.h.

       If you experience difficulty in allocating space	on the ufs filesystem,
       if may be due to	framentation. Fragmentation can	occur when you do  not
       have  sufficient	 free  blocks  to  satisfy  an allocation request even
       though df(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  fstyp(1M)
       utility with the	-v option. In the fstyp	output,	 look  at  the	nbfree
       (number	of  blocks  free)  and	 nffree	 (number  of  fragments	 free)
       fields. On unmounted filesystems, you can use fsck(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 ufsdump(1M)	and ufsrestore(1M) on the ufs filesystem.

				  25 Jun 2003			      ufs(7FS)

NAME | SYNOPSIS | NOTES

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