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FSCK_EXT2FS(8) System Manager's Manual FSCK_EXT2FS(8)
NAME
fsck_ext2fs - ext2 File System consistency check and interactive repair
SYNOPSIS
fsck_ext2fs [-dfnpUy] [-b block#] [-m mode] filesystem ...
DESCRIPTION
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
failures intervene. 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
successfully 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
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 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 action.
The following flags are interpreted by fsck_ext2fs.
-b 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 file systems. Normally, if a file system is
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 file system,
regardless of the state of the clean flag.
-m Use the mode specified in octal immediately after the flag 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 restrictive set of permissions such as 700.
-n Assume a no response to all questions asked by fsck_ext2fs except
for `CONTINUE?', which is assumed to be affirmative; do not open
the filesystem for writing.
-p Specify "preen" mode, described above.
-U Resolve numeric userids to usernames.
-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
encountered.
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
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.
DIAGNOSTICS
The diagnostics produced by fsck_ext2fs are fully enumerated and
explained in Appendix A of Fsck - The UNIX File System Check Program.
SEE ALSO
fs(5), fstab(5), fsck(8), fsdb(8), newfs(8), reboot(8)
HISTORY
A fsck_ext2fs utility appeared in NetBSD 1.3.
AUTHORS
fsck_ext2fs was written by Manuel Bouyer <bouyer@NetBSD.org>.
NetBSD 10.99 August 27, 2018 NetBSD 10.99