FSCK(8)FSCK(8)NAMEfsck - file system consistency check and interactive repair
SYNOPSISfsck-p [ -m mode ]
fsck [ -b block# ] [ -c ] [ -y ] [ -n ] [ -m mode ] [ filesystem ] ...
DESCRIPTION
The first form of fsck preens a standard set of filesystems or the
specified file systems. It is normally used in the script /etc/rc dur‐
ing automatic reboot. Here fsck reads the table /etc/fstab to deter‐
mine which file systems to check. Only partitions in fstab that are
mounted ``rw,'' ``rq'' or ``ro'' and that have non-zero pass number are
checked. Filesystems with pass number 1 (normally just the root
filesystem) are checked one at a time. When pass 1 completes, all
remaining filesystems are checked, running one process per disk drive.
The disk drive containing each filesystem is inferred from the longest
prefix of the device name that ends in a digit; the remaining charac‐
ters are assumed to be the partition designator.
The system takes care that only a restricted class of innocuous incon‐
sistencies 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 with the -p option will
correct; if it encounters other inconsistencies, it exits with an
abnormal return status and an automatic reboot will then fail. For
each corrected inconsistency one or more lines will be printed identi‐
fying the file system on which the correction will take place, and the
nature of the correction. After successfully correcting a file system,
fsck will print the number of files on that file system, the number of
used and free blocks, and the percentage of fragmentation.
If sent a QUIT signal, fsck will finish the file system checks, then
exit with an abnormal return status that causes an automatic reboot to
fail. This is useful when to finish the file system checks during an
automatic reboot, but do not want the machine to come up multiuser
after the checks complete.
Without the -p option, fsck audits and interactively repairs inconsis‐
tent 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 -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 correc‐
tion is to wait for the operator to respond yes or no. If the operator
does not have write permission on the file system fsck will default to
a -n action.
Fsck has more consistency checks than its predecessors check, dcheck,
fcheck, and icheck combined.
The following flags are interpreted by fsck.
-b Use the block specified immediately after the flag as the super
block for the file system. Block 32 is usually an alternate
super block.
-l Limit the number of parallel checks to the number specified in
the following argument. By default, the limit is the number of
disks, running one process per disk. If a smaller limit is
given, the disks are checked round-robin, one filesystem at a
time.
-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.
-y Assume a yes response to all questions asked by fsck; this should
be used with great caution as this is a free license to continue
after essentially unlimited trouble has been encountered.
-n Assume a no response to all questions asked by fsck except for
``CONTINUE?'', which is assumed to be affirmative; do not open
the file system for writing.
-c If the file system is in the old (static table) format, convert
it to the new (dynamic table) format. If the file system is in
the new format, convert it to the old format provided the old
format can support the filesystem configuration. In interactive
mode, fsck will list the direction the conversion is to be made
and ask whether the conversion should be done. If a negative
answer is given, no further operations are done on the filesys‐
tem. In preen mode, the direction of the conversion is listed
and done if possible without user interaction. Conversion in
preen mode is best used when all the file systems are being con‐
verted at once. The format of a file system can be determined
from the first line of output from dumpfs(8).
If no filesystems are given to fsck then a default list of file systems
is read from the file /etc/fstab.
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 file system.
3. Incorrect link counts.
4. Size checks:
Directory size not of proper format.
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 file system.
9. Bad free block map format.
10. 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 insuf‐
ficient space its size is increased.
Because of inconsistencies between the block device and the buffer
cache, the raw device should always be used.
FILES
/etc/fstab contains default list of file systems to check.
DIAGNOSTICS
The diagnostics produced by fsck are fully enumerated and explained in
Appendix A of ``Fsck - The UNIX File System Check Program'' (SMM:5).
SEE ALSOfstab(5), fs(5), fsdb(8), newfs(8), mkfs(8), reboot(8)4th Berkeley Distribution February 1, 1990 FSCK(8)
