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 direc-
       tory (/) and continuing downward through a number of directories. The root of a UFS file system is inode 2. A UFS file system's  root  con-
       tents replace 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 modified data in memory. A mounted file system with this state flag  indi-
                               cates 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 indicates that neither user data
                               nor metadata would be lost if power to the system is interrupted.

       FSBAD                   Indicates that this file system contains inconsistent file system data.

       FSLOG                   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 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 con-
       stant integer defined in the /usr/include/sys/fs/ufs_fs.h file.  Otherwise, fs_clean is treated as though it contains the  value  of  FSAC-
       TIVE.

   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 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.

       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/include/sys/fs/ufs_fs
            file.

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

   UFS Logging
       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.

       UFS logging provides two advantages:

       1.  A file system that is consistent with the transaction log eliminates the need to run fsck after a system crash or an unclean shutdown.

       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.

       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
       maximum 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 commands,
       see ufsdump(1M), ufsrestore(1M), and /usr/include/protocols/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  frag-
       ments 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)