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FSCK_FFS(8)                 System Manager's Manual                FSCK_FFS(8)

     fsck_ffs - Fast File System consistency check and interactive repair

     fsck_ffs [-adFfPpqUXz] [-B byteorder] [-b block] [-c level] [-m mode]
              [-x snap-backup] [-y | -n] filesystem ...

     fsck_ffs performs interactive file system consistency checks and repair
     for each of the file systems specified on the command line.  It is
     normally invoked from fsck(8).

     The kernel takes care that only a restricted class of innocuous file
     system inconsistencies can happen unless hardware or software failures
     intervene.  These are limited to the following:

           Unreferenced inodes
           Link counts in inodes too large
           Missing blocks in the free map
           Blocks in the free map also in files
           Counts in the super-block wrong

     These are the only inconsistencies that fsck_ffs in "preen" mode (with
     the -p option) will correct; if it encounters other inconsistencies, it
     exits with an abnormal return status.  For each corrected inconsistency
     one or more lines will be printed identifying the file system on which
     the correction will take place, and the nature of the correction.  After
     successfully correcting a file system, fsck_ffs will print the number of
     files on that file system, the number of used and free blocks, and the
     percentage of fragmentation.

     If sent a QUIT signal, fsck_ffs will finish the file system checks, then
     exit with an abnormal return status.

     If fsck_ffs receives a SIGINFO signal (see the status argument for
     stty(1)), a line will be written to the standard error output indicating
     the name of the device currently being checked, the current phase number
     and phase-specific progress information.

     Without the -p option, fsck_ffs audits and interactively repairs
     inconsistent conditions for file systems.  If the file system is
     inconsistent the operator is prompted for concurrence before each
     correction is attempted.  It should be noted that some of the corrective
     actions which are not correctable under the -p option will result in some
     loss of data.  The amount and severity of data lost may be determined
     from the diagnostic output.  The default action for each consistency
     correction is to wait for the operator to respond yes or no.  If the
     operator does not have write permission on the file system fsck_ffs will
     default to a -n action.

     fsck_ffs has more consistency checks than its predecessors check, dcheck,
     fcheck, and icheck combined.

     The following flags are interpreted by fsck_ffs.

           -a              Interpret the filesystem as an Apple UFS
                           filesystem, even if there is no Apple UFS volume
                           label present.

           -B byteorder    Convert the file system metadata to byteorder byte
                           order if needed.  Valid byte orders are "be" and
                           "le".  If fsck_ffs is interrupted while swapping
                           the metadata byte order, the file system cannot be
                           recovered.  fsck_ffs will print a message in
                           interactive mode if the file system is not in host
                           byte order.

           -b block        Use the block number block as the super block for
                           the file system.  Block 32 is usually an
                           alternative super block.  The -b option of the
                           scan_ffs(8) utility can also be used to find the
                           offset of other super block backups in a file

           -c level        Convert the FFSv1 file system to the level level.
                           Note that the level of a file system can only be
                           raised.  There are currently five levels defined:

                                 0    The file system is in the old (static
                                      table) format.

                                 1    The file system is in the new (dynamic
                                      table) format.  Such file systems are
                                      made by using the -O 0 option to

                                 2    The file system supports 32-bit UIDs and
                                      GIDs, short symbolic links are stored in
                                      the inode, and directories have an added
                                      field showing the file type.  This
                                      format was introduced in 4.4BSD.

                                 3    If maxcontig is greater than one, build
                                      the free segment maps to aid in finding
                                      contiguous sets of blocks.  If maxcontig
                                      is equal to one, delete any existing
                                      segment maps.  This was the default
                                      before NetBSD 2.0.

                                 4    Rearrange the super block to the same
                                      layout as FFSv2; disable the rotational
                                      layout tables and per cylinder group
                                      block totals.  Such file systems are
                                      made by using the -O 1 option to

                           Note that FFSv2 file systems always have the
                           features of FFSv1 level 4.

                           FFSv2 file systems have separate conversion

                                 ea   Convert the file system to the format
                                      which supports extended attributes (and
                                      access control lists).  After this
                                      conversion is performed, the file system
                                      will no longer be recognized at all by
                                      releases prior to NetBSD 10.0.

                                      Convert the file system to the format
                                      which does not support extended
                                      attributes (or access control lists).
                                      This will remove any existing extended
                                      attributes, and the file system will
                                      become recognizable to releases prior to
                                      NetBSD 10.0.

                           In interactive mode, fsck_ffs will list the
                           conversion to be made and ask whether the
                           conversion should be done.  If a negative answer is
                           given, no further operations are done on the file
                           system.  In preen mode, the conversion is listed
                           and done if possible without user interaction.
                           Conversion in preen mode is best used when all the
                           file systems are being converted at once.

                           The output of dumpfs(8) can be examined to
                           determine the format of the file system ("format"
                           in the second line) and the file system level
                           ("fslevel" in the sixth line).

           -d              Print debugging output.

           -F              Indicates that filesystem is a file system image,
                           rather than a raw character device.  filesystem
                           will be accessed `as-is', and no attempts will be
                           made to read a disklabel.

           -f              Force checking of file systems.  Normally, if a
                           file system is cleanly unmounted, the kernel will
                           set a "clean flag" in the file system super block,
                           and fsck_ffs will not check the file system.  This
                           option forces fsck_ffs to check the file system,
                           regardless of the state of the clean flag.

           -m mode         Use the octal value mode as the permission bits to
                           use when creating the lost+found directory rather
                           than the default 1700.  In particular, systems that
                           do not wish to have lost files accessible by all
                           users on the system should use a more restrictive
                           set of permissions such as 700.

           -n              Assume a no response to all questions asked by
                           fsck_ffs except for `CONTINUE?', which is assumed
                           to be affirmative; do not open the file system for

           -P              Display a progress meter for the file system check.
                           A new meter is displayed for each of the 5 file
                           system check passes, unless -p is specified, in
                           which case only one meter for overall progress is
                           displayed.  Progress meters are disabled if the -d
                           option is specified.

           -p              Specify "preen" mode, described above.

           -q              Quiet mode, do not output any messages for clean

           -U              Resolve user ids to usernames.

           -X              Similar to -x but uses a file system internal
                           snapshot on the file system to be checked.

           -x snap-backup  Use a snapshot with snap-backup as backup to check
                           a read-write mounted filesystem.  Must be used with
                           -n.  See fss(4) for more details.  The point is to
                           check an internally-consistent version of the
                           filesystem to find out if it is damaged; on failure
                           one should unmount the filesystem and repair it.

           -y              Assume a yes response to all questions asked by
                           fsck_ffs; this should be used with great caution as
                           this is a free license to continue after
                           essentially unlimited trouble has been encountered.

           -z              Clear unused directory space.  The cleared space
                           includes deleted file names and name padding.

     Inconsistencies checked are as follows:
           1.   Blocks claimed by more than one inode or the free map.
           2.   Blocks claimed by an inode outside the range of the file
           3.   Incorrect link counts.
           4.   Size checks:
                      Directory size not a multiple of DIRBLKSIZ.
                      Partially truncated file.
           5.   Bad inode format.
           6.   Blocks not accounted for anywhere.
           7.   Directory checks:
                      File pointing to unallocated inode.
                      Inode number out of range.
                      Dot or dot-dot not the first two entries of a directory
                      or having the wrong inode number.
           8.   Super Block checks:
                      More blocks for inodes than there are in the file
                      Bad free block map format.
                      Total free block and/or free inode count incorrect.

     Orphaned files and directories (allocated but unreferenced) are, with the
     operator's concurrence, reconnected by placing them in the lost+found
     directory.  The name assigned is the inode number.  If the lost+found
     directory does not exist, it is created.  If there is insufficient space
     its size is increased.

     Because of inconsistencies between the block device and the buffer cache,
     the raw device should always be used.

     The diagnostics produced by fsck_ffs are fully enumerated and explained
     in Appendix A of Fsck - The UNIX File System Check Program.

     fss(4), fs(5), fstab(5), dumpfs(8), fsck(8), fsdb(8), newfs(8),
     reboot(8), scan_ffs(8)

     A fsck utility appeared in 4.0BSD.  It was renamed to fsck_ffs in
     NetBSD 1.3 with the introduction of a filesystem independent wrapper as

NetBSD 10.99                      May 4, 2018                     NetBSD 10.99