FSCK_EXT2FS(8) BSD System Manager's Manual FSCK_EXT2FS(8)
fsck_ext2fs - Second Extended Filesystem consistency check and interac-
tive repair
fsck_ext2fs [-dfnpy] [-b block#] [-m mode] filesystem ...
fsck_ext2fs performs interactive filesystem consistency checks and
repairs for each of the filesystems specified. It is normally invoked
from fsck(8).
The kernel takes care that only a restricted class of innocuous filesys-
tem inconsistencies can happen unless hardware or software failures in-
tervene. These are limited to the following:
Unreferenced inodes
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 "preen" mode (with
the -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 filesystem on which the
correction will take place, and the nature of the correction. After suc-
cessfully correcting a filesystem, fsck_ext2fs will print the number of
files on that filesystem and the number of used and free blocks.
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 repairs in-
consistent conditions for filesystems. If the filesystem is inconsistent,
the operator is prompted for concurrence before each correction is at-
tempted. 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 the diagnostic
output. The default action for each consistency correction is to wait for
the operator to respond "yes" or "no". If the operator does not have
write permission on the filesystem, fsck_ext2fs will default to a -n ac-
tion.
The following flags are interpreted by fsck_ext2fs:
-b block#
Use the block specified immediately after the flag as the super
block for the filesystem. Block 8193 is usually an alternate
super block.
-d Print debugging output.
-f Force checking of filesystems. Normally, if a filesystem is
cleanly unmounted, the kernel will set a "clean flag" in the
filesystem superblock and fsck_ext2fs will not check the filesys-
tem. This option forces fsck_ext2fs to check the filesystem, re-
gardless of the state of the clean flag.
-m mode
Use the mode specified in octal as the permission bits to use
when creating the 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 restric-
tive set of permissions such as 700.
-n Assume a "no" response to all questions asked by fsck_ext2fs ex-
cept for "CONTINUE?", which is assumed to be affirmative.
Filesystems will not be opened for writing. This is the default
for filesystems to be checked that are concurrently mounted writ-
able.
-p Specify "preen" mode, described above.
-y Assume a "yes" response to all questions asked by fsck_ext2fs;
this should be used with great caution as this is a free license
to continue after essentially unlimited trouble has been encoun-
tered.
Inconsistencies checked are as follows:
1. Blocks claimed more than once by inodes or the free map.
2. Blocks claimed by an inode outside the range of the filesystem.
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 or
having 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 lost+found
directory. The name assigned is the inode number. If the lost+found
directory does not exist, it is created. If there is insufficient space
its size is increased.
Because of inconsistencies between the block device and the buffer cache,
the raw device should always be used.
The diagnostics produced by fsck_ext2fs are fully enumerated and ex-
plained in Appendix A of fsck_ffs - The UNIX(R) Filesystem Check Program.
fs(5), fstab(5), fsck(8), mount_ext2fs(8), rc(8)
Marshall Kirk McKusick, fsck_ffs - The UNIX(R) Filesystem Check Program,
03.fsck_ffs(SMM).
MirBSD #10-current June 13, 1997 1