.\"	$OpenBSD: fsck_ext2fs.8,v 1.16 2010/01/10 10:53:33 jmc Exp $
.\"	$NetBSD: fsck_ext2fs.8,v 1.1 1997/06/11 11:21:48 bouyer Exp $
.\"
.\" Copyright (c) 1997 Manuel Bouyer.
.\" Copyright (c) 1980, 1989, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\"
.\"	@(#)fsck.8	8.3 (Berkeley) 11/29/94
.\"
.Dd $Mdocdate: January 10 2010 $
.Dt FSCK_EXT2FS 8
.Os
.Sh NAME
.Nm fsck_ext2fs
.Nd Second Extended File System consistency check and interactive repair
.Sh SYNOPSIS
.Nm fsck_ext2fs
.Op Fl dfnpy
.Op Fl b Ar block#
.Op Fl m Ar mode
.Ar filesystem ...
.Sh DESCRIPTION
.Nm
performs interactive file system consistency checks and repairs for each of
the file systems 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
in
.Dq 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
and the number of used and free blocks.
.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
.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
The following flags are interpreted by
.Nm fsck_ext2fs :
.Bl -tag -width indent
.It Fl b Ar block#
Use the block specified immediately after the flag as
the super block for the file system.
Block 8193 is usually an alternate super block.
.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 the
.Ar mode
specified in octal as the
permission bits to use when creating the
.Pa lost+found
directory rather than the default 1777.
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
.Dq no
response to all questions asked by
.Nm
except for
.Dq CONTINUE? ,
which is assumed to be affirmative.
File systems will not be opened for writing.
This is the default for file systems to be checked that are
concurrently mounted writable.
.It Fl p
Specify
.Dq preen
mode, described above.
.It Fl y
Assume a
.Dq yes
response to all questions asked by
.Nm fsck_ext2fs ;
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:
.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 file system block size.
.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 mount_ext2fs 8 ,
.Xr rc 8