fsck_ext2fs - Second Extended File System consistency check
fsck_ext2fs [-b block#] [-d] [-f] [-m mode] [-p] [-y] [-n]
fsck_ext2fs performs interactive filesystem consistency
checks and repair
for each of the filesystems specified on the command line.
It is normally
invoked from fsck(8).
The kernel takes care that only a restricted class of innocuous filesystem
inconsistencies can happen unless hardware or software
These are limited to the following:
Link counts in inodes too large
Missing blocks in the free map
Blocks in the free map also in files
Counts in the super-block wrong
These are the only inconsistencies that fsck_ext2fs in
(with the -p option) will correct; if it encounters other
it exits with an abnormal return status. For each
one or more lines will be printed identifying the
which the correction will take place, and the nature of the
After successfully correcting a filesystem, fsck_ext2fs will
number of files on that filesystem and the number of used
If sent a QUIT signal, fsck_ext2fs will finish the filesystem checks,
then exit with an abnormal return status.
Without the -p option, fsck_ext2fs audits and interactively
conditions for filesystems. If the filesystem is
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 -p option will result in some
loss of data.
The amount and severity of data lost may be determined from
output. The default action for each consistency correction is to
wait for the operator to respond ``yes'' or ``no''. If the
not have write permission on the filesystem, fsck_ext2fs
will default to
a -n action.
The following flags are interpreted by fsck_ext2fs:
Use the block specified immediately after the flag
as the super
block for the filesystem. Block 8193 is usually an
-d Print debugging output.
-f Force checking of file systems. Normally, if a file
cleanly unmounted, the kernel will set a ``clean
flag'' in the
file system superblock and fsck_ext2fs will not
check the file
system. This option forces fsck_ext2fs to check the
regardless of the state of the clean flag.
Use the mode specified in octal as the permission
bits to use
when creating the lost+found directory rather than
1777. In particular, systems that do not wish to
have lost files
accessible by all users on the system should use a
set of permissions such as 700.
-n Assume a ``no'' response to all questions asked by
except for ``CONTINUE?'', which is assumed to be affirmative; do
not open the filesystem for writing.
-p Specify ``preen'' mode, described above.
-y Assume a ``yes'' response to all questions asked by
this should be used with great caution as this is a
to continue after essentially unlimited trouble has
Inconsistencies checked are as follows:
1. Blocks claimed by more than one inode or the free map.
2. Blocks claimed by an inode outside the range of the
3. Incorrect link counts.
4. Size checks:
Directory size not a multiple of filesystem block size.
Partially truncated file.
5. Bad inode format.
6. Blocks not accounted for anywhere.
7. Directory checks:
File pointing to unallocated inode.
Inode number out of range.
Dot or dot-dot not the first two entries of a directory
the wrong inode number.
8. Super Block checks:
More blocks for inodes than there are in the filesystem.
Bad free block map format.
Total free block and/or free inode count incorrect.
Orphaned files and directories (allocated but unreferenced)
are, with the
operator's concurrence, reconnected by placing them in the
The name assigned is the inode number. If the
does not exist, it is created. If there is insufficient space
its size is increased.
Because of inconsistencies between the block device and the
the raw device should always be used.
The diagnostics produced by fsck_ext2fs are fully enumerated
in Appendix A of Fsck - The UNIX File System Check
fs(5), fstab(5), fsck(8), fsdb(8), newfs(8), reboot(8)
OpenBSD 3.6 June 13, 1997
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