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.\"	@(#)fsck.8	8.3 (Berkeley) 11/29/94
.\"
.Dd $Mdocdate: September 1 2016 $
.Dt FSCK_FFS 8
.Os
.Sh NAME
.Nm fsck_ffs
.Nd Fast File System consistency check and interactive repair
.Sh SYNOPSIS
.Nm fsck_ffs
.Op Fl fnpy
.Op Fl b Ar block#
.Op Fl c Ar level
.Op Fl m Ar mode
.Ar filesystem
.Sh DESCRIPTION
.Nm
performs interactive file system consistency checks and repairs the
file system specified.
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 -offset indent
.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
with the
.Fl p
option will correct; if it encounters other inconsistencies, it exits
with an abnormal return status and an automatic reboot will then fail.
For each corrected inconsistency, one or more lines will be printed
identifying the file system on which the correction will take place
along with 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 that causes an automatic reboot to fail.
This is useful when you want to finish the file system checks during an
automatic reboot,
but do not want the machine to come up multiuser after the checks complete.
.Pp
If sent an
.Dv INFO
signal,
.Nm
will print a line to standard error indicating the name of the device
currently being checked, the current phase number, and phase-specific
progress information.
.Pp
Without the
.Fl p
option,
.Nm
audits and interactively repairs inconsistent conditions for the filesystem.
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
.Dq yes
or
.Dq no .
If the operator does not have write permission on the file system,
.Nm
will default to a
.Fl n
action.
.Pp
.Nm fsck
has more consistency checks than
its predecessors
.Em check , dcheck , fcheck ,
and
.Em icheck
combined.
.Pp
The following flags are interpreted by
.Nm fsck_ffs :
.Bl -tag -width indent
.It Fl b Ar block#
Use the
.Ar block#
specified as
the super block for the file system.
If the primary superblock is corrupted
.Nm
tries to find a valid alternate superblock based on the
information in the disklabel.
If that fails, a number printed by
.Nm newfs
(using
.Fl N
combined with the original flags used to create the filesystem)
can be used as a value to this argument.
.It Fl c Ar level
Convert the file system to the specified
.Ar level .
Note that the level of a file system can only be raised.
There are currently four levels defined:
.Bl -tag -width indent
.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 UIDs and GIDs,
short symbolic links are stored in the inode,
and directories have an added field showing the file type.
.It 3
If
.Va maxcontig
is greater than one,
build the free segment maps to aid in finding contiguous sets of blocks.
If
.Va maxcontig
is equal to one, delete any existing segment maps.
.El
.It Fl f
Force checking of the filesystem.
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 Ar mode
Use the
.Ar mode
specified in octal as the
permission bits to use when creating the
.Pa lost+found
directory rather than the default 1700.
In particular, systems that wish to have lost files accessible
by all users on the system should use a less restrictive
set of permissions such as 755.
.It Fl n
Assume a
.Dq no
response to all questions asked by
.Nm
except for
.Dq CONTINUE? ,
which is assumed to be affirmative.
The filesystem will not be opened for writing.
This is the default for file systems to be checked that are
concurrently mounted writable.
.It Fl p
Enter preen mode:
.Nm
will check the filesystem on the
special (raw) device listed on the command line
and will make minor repairs without
human intervention.
Any major problems will cause
.Nm
to exit with a non-zero exit code,
so as to alert any invoking program or script
that human intervention is required.
.It Fl y
Assume a
.Dq yes
response to all questions asked by
.Nm fsck_ffs ;
this should be used with great caution as this is a free license
to continue after essentially unlimited trouble has been encountered.
.El
.Pp
If neither of the
.Fl y
or
.Fl n
options are specified, the user may force
.Nm
to assume an answer of
.Dq yes
to all the remaining questions by replying to a question with a value of
.Dq F .
.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
first line of output from
.Xr dumpfs 8 .
.Pp
Inconsistencies checked are as follows:
.Pp
.Bl -enum -compact
.It
Blocks claimed more than once by inodes 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 -compact -offset indent
.It
Directory size not a multiple of
.Dv DIRBLKSIZ .
.It
Partially truncated file.
.El
.It
Bad inode format.
.It
Blocks not accounted for anywhere.
.It
Directory checks:
.Bl -item -compact -offset indent
.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 -compact -offset indent
.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_ffs \- The UNIX File System Check Program"
.Re
.Sh SEE ALSO
.Xr fs 5 ,
.Xr fstab 5 ,
.Xr fsck 8 ,
.Xr fsdb 8 ,
.Xr growfs 8 ,
.Xr mount_ffs 8 ,
.Xr newfs 8 ,
.Xr rc 8 ,
.Xr scan_ffs 8