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.\"	@(#)fsck.8	8.3 (Berkeley) 11/29/94
.\"
.Dd November 16, 2001
.Dt FSCK_FFS 8
.Os
.Sh NAME
.Nm fsck_ffs
.Nd Fast File System consistency check and interactive repair
.Sh SYNOPSIS
.Nm ""
.Op Fl B Ar byte order
.Op Fl b Ar block#
.Op Fl c Ar level
.Op Fl d
.Op Fl F
.Op Fl f
.Op Fl m Ar mode
.Op Fl p
.Op Fl y
.Op Fl n
.Ar filesystem ...
.Sh DESCRIPTION
.Nm
performs interactive file system consistency checks and repair for each of
the file systems specified on the command line. It is normally invoked from
.Xr fsck 8 .
.Pp
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:
.Pp
.Bl -item -compact
.It
Unreferenced inodes
.It
Link counts in inodes too large
.It
Missing blocks in the free map
.It
Blocks in the free map also in files
.It
Counts in the super-block wrong
.El
.Pp
These are the only inconsistencies that
.Nm
in ``preen''
mode (with the
.Fl 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,
.Nm
will print the number of files on that file system,
the number of used and free blocks,
and the percentage of fragmentation.
.Pp
If sent a
.Dv QUIT
signal,
.Nm
will finish the file system checks, then exit with an abnormal return status.
.Pp
Without the
.Fl p
option,
.Nm
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
.Fl 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
.Li yes
or
.Li no .
If the operator does not have write permission on the file system
.Nm
will default to a 
.Fl n
action.
.Pp
.Nm
has more consistency checks than
its predecessors
.Em check , dcheck , fcheck ,
and
.Em icheck
combined.
.Pp
The following flags are interpreted by
.Nm "" .
.Bl -tag -width indent
.It Fl B
Convert the file system metadata to the specified byte order if needed.
Valid byte order are `be' and `le'. If
.Nm ""
is interrupted while swapping the metadata byte order, the file system cannot
be recovered. 
.Nm "" 
will print a message in interactive mode if the file system is not in host
byte order.
.It Fl b
Use the block specified immediately after the flag as
the super block for the file system.  Block 32 is usually
an alternative super block.
.It Fl c
Convert the file system to the specified level.
Note that the level of a file system can only be raised.
.Bl -tag -width indent
There are currently four levels defined:
.It 0
The file system is in the old (static table) format.
.It 1
The file system is in the new (dynamic table) format.
.It 2
The file system supports 32-bit uid's and gid's,
short symbolic links are stored in the inode, 
and directories have an added field showing the file type.
.It 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.
.El
.Pp
In interactive mode,
.Nm
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 format of a file system can be determined from the
second line of output from 
.Xr dumpfs 8 .
.It Fl d
Print debugging output.
.It Fl F
Indicates that
.Ar filesystem
is a file system image, rather than a raw character device.
.Ar filesystem
will be accessed
.Sq as-is ,
and no attempts will be made to read a disklabel.
.It Fl f
Force checking of file systems.  Normally, if a file system is cleanly
unmounted, the kernel will set a
.Dq clean flag
in the file system superblock, and
.Nm
will not check the file system.  This option forces
.Nm
to check the file system, regardless of the state of the clean flag.
.It Fl m
Use the mode specified in octal immediately after the flag as the
permission bits to use when creating the
.Pa 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.
.It Fl n
Assume a no response to all questions asked by 
.Nm
except for
.Ql CONTINUE? ,
which is assumed to be affirmative;
do not open the file system for writing.
.It Fl p
Specify ``preen'' mode, described above.
.It Fl y
Assume a yes response to all questions asked by 
.Nm "" ;
this should be used with great caution as this is a free license
to continue after essentially unlimited trouble has been encountered.
.El
.Pp
.Bl -enum -indent indent -compact
Inconsistencies checked are as follows:
.It
Blocks claimed by more than one inode or the free map.
.It
Blocks claimed by an inode outside the range of the file system.
.It
Incorrect link counts.
.It
Size checks:
.Bl -item -indent indent -compact
.It 
Directory size not a multiple of DIRBLKSIZ.
.It
Partially truncated file.
.El
.It
Bad inode format.
.It
Blocks not accounted for anywhere.
.It
Directory checks:
.Bl -item -indent indent -compact
.It 
File pointing to unallocated inode.
.It
Inode number out of range.
.It
Dot or dot-dot not the first two entries of a directory
or having the wrong inode number.
.El
.It
Super Block checks:
.Bl -item -indent indent -compact
.It 
More blocks for inodes than there are in the file system.
.It
Bad free block map format.
.It
Total free block and/or free inode count incorrect.
.El
.El
.Pp
Orphaned files and directories (allocated but unreferenced) are,
with the operator's concurrence, reconnected by
placing them in the 
.Pa lost+found
directory.
The name assigned is the inode number.
If the
.Pa lost+found
directory does not exist, it is created.
If there is insufficient space its size is increased.
.Pp
Because of inconsistencies between the block device and the buffer cache,
the raw device should always be used.
.Sh DIAGNOSTICS
The diagnostics produced by 
.Nm
are fully enumerated and explained in Appendix A of
.Rs
.%T "Fsck \- The UNIX File System Check Program"
.Re
.Sh SEE ALSO
.Xr fstab 5 ,
.Xr fs 5 ,
.Xr fsdb 8 ,
.Xr newfs 8 ,
.Xr reboot 8 ,
.Xr fsck 8