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.\"	@(#)fsck.8	8.3 (Berkeley) 11/29/94
.\"
.Dd March 17, 1999
.Dt FSCK_LFS 8
.Os NetBSD
.Sh NAME
.Nm fsck_lfs
.Nd Log-structured File System consistency check and interactive repair
.Sh SYNOPSIS
.Nm fsck_lfs
.Op Fl b Ar block#
.Op Fl d
.\" .Op Fl m
.\" .Op Fl f
.Op Fl p
.Op Fl y
.Op Fl n
.Ar filesystem
.Ar ...
.Sh DESCRIPTION
.Nm Fsck_lfs
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 Fsck_lfs
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 fsck_lfs
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 fsck_lfs
will finish the filesystem checks, then exit with an abnormal return status.
.Pp
Without the
.Fl p
option,
.Nm fsck_lfs
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 fsck_lfs
will default to a 
.Fl n
action.
.Pp
The following flags are interpreted by
.Nm fsck_lfs .
.Bl -tag -width indent
.It Fl b
Use the block specified immediately after the flag 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
.\" 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 fsck_lfs
except for
.Ql CONTINUE? ,
which is assumed to be affirmative;
do not open the filesystem for writing.
.It Fl p
Specify ``preen'' mode.  Currently, in this mode
.Nm fsck_lfs
simply checks validity of the newer checkpoint.
.It Fl y
Assume a yes response to all questions asked by 
.Nm fsck_lfs ;
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.
.It
Blocks claimed by an inode outside the range of the filesystem.
.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
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 filesystem.
.It
Segment block counts incorrect, or ``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 fsck_lfs
are fully enumerated and explained in Appendix A of
.Rs
.%T "Fsck \- The UNIX File System Check Program"
.Re
.Sh BUGS
.Nm Fsck_lfs
cannot currently perform a full roll-forward, or correct all of the
errors that it can detect.
.Sh HISTORY
The
.Nm
program was first made available in
.Nx 1.4 .
.Sh AUTHOR
Most of the
.Nm
program was taken from
.Xr fsck_ffs 8 ;
what was not was written by Konrad Schroder <perseant@hhhh.org>.
.Sh SEE ALSO
.Xr fstab 5 ,
.Xr newlfs 8 ,
.Xr reboot 8 ,
.Xr fsck 8