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.\"	@(#)fsck.8	8.3 (Berkeley) 11/29/94
.\"
.Dd July 12, 2014
.Dt FSCK_LFS 8
.Os
.Sh NAME
.Nm fsck_lfs
.Nd Log-structured File System consistency check and interactive repair
.Sh SYNOPSIS
.Nm fsck_lfs
.Op Fl dfpqU
.Op Fl b Ar block
.Op Fl m Ar mode
.Op Fl y | n
.Ar filesystem
.Ar ...
.Sh DESCRIPTION
.Nm
performs interactive filesystem consistency checks and repair for
each of the filesystems specified on the command line.
It is normally invoked from
.Xr fsck 8 .
.Pp
The design of LFS takes care that no filesystem inconsistencies can
happen unless hardware or software failures intervene.
.Nm
will report and optionally correct any such inconsistencies.
.Pp
For each corrected inconsistency one or more lines will be printed
identifying the filesystem on which the correction will take place,
and the nature of the correction.
After successfully correcting a filesystem,
.Nm
will print the number of files on that filesystem,
the number of used and free blocks,
and the percentage of fragmentation.
.Pp
If sent a
.Dv QUIT
signal,
.Nm
will finish the filesystem checks, then exit with an abnormal return status.
.Pp
Without the
.Fl p
option,
.Nm
audits and interactively repairs inconsistent conditions for filesystems.
If the filesystem is inconsistent, the operator is prompted for concurrence
before each correction is attempted.
It should be noted that some of the corrective actions 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 filesystem
.Nm
will default to a
.Fl n
action.
.Pp
The following flags are interpreted by
.Nm :
.Bl -tag -width XbXblockXX
.It Fl b Ar block
Use
.Ar block
as the super block for the filesystem.
.It Fl d
Print debugging output.
.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 Ar mode
Use
.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 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 filesystem for writing.
.It Fl p
Specify
.Dq preen
mode.
Currently, in this mode
.Nm
does nothing.
.\" rolls forward from the older checkpoint, and performs no other action.
.It Fl q
Quiet mode, do not output any messages for clean filesystems.
.It Fl U
Resolve user ids to user names.
.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
Inconsistencies checked are as follows:
.Bl -enum -offset indent -compact
.It
Blocks claimed by more than one inode.
.It
Blocks claimed by an inode outside the range of the filesystem.
.It
Incorrect link counts.
.It
Size checks:
.Bl -item -offset indent -compact
.It
Directory size not a multiple of DIRBLKSIZ.
.It
Partially truncated file.
.El
.It
Bad inode format.
.It
Directory checks:
.Bl -item -offset 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 -offset indent -compact
.It
More blocks for inodes than there are in the filesystem.
.El
.It
Index File checks:
.Bl -item -offset indent -compact
.It
.Dq \&In use
inodes on free list, or free inodes not on free list.
.It
Segment block counts incorrect, or
.Dq clean
segments containing live data.
.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 fsck 8 ,
.Xr newfs_lfs 8 ,
.Xr reboot 8
.Sh HISTORY
The
.Nm
program was first made available in
.Nx 1.4 .
.Sh AUTHORS
Most of the
.Nm
program was taken from
.Xr fsck_ffs 8 ;
what was not was written by
.An Konrad Schroder Aq Mt perseant@NetBSD.org .