The specified disk partitions and/or file systems are checked.
In "preen" or "check clean" mode the clean flag of each file system's
superblock is examined and only those file systems that are not marked clean
File systems are marked clean when they are unmounted,
when they have been mounted read-only, or when
runs on them successfully.
option is specified, the file systems
will be checked regardless of the state of their clean flag.
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:
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
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
identifying the file system on which the correction will take place,
and the nature of the correction.
After successfully correcting a file system,
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
will finish the file system checks, then exit with an abnormal
return status that causes an automatic reboot to fail.
This is useful when you want to finish the file system checks during an
but do not want the machine to come up multiuser after the checks complete.
signal, a line will be written to the standard output indicating
the name of the device currently being checked, the current phase
number and phase-specific progress information.
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
option will result in some loss of data.
The amount and severity of data lost may be determined from the diagnostic
The default action for each consistency correction
is to wait for the operator to respond
If the operator does not have write permission on the file system
will default to a
The following flags are interpreted by
Determine whether the file system needs to be cleaned immediately
in foreground, or if its cleaning can be deferred to background.
To be eligible for background cleaning it must have been running
with soft updates, not have been marked as needing a foreground check,
and be mounted and writable when the background check is to be done.
If these conditions are met, then
exits with a zero exit status.
Otherwise it exits with a non-zero exit status.
If the file system is clean,
it will exit with a non-zero exit status so that the clean status
of the file system can be verified and reported during the foreground
Note that when invoked with the
flag, no cleanups are done.
The only thing that
does is to determine whether a foreground or background
check is needed and exit with an appropriate status code.
A check is done on the specified and possibly active file system.
The set of corrections that can be done is limited to those done
when running in preen mode (see the
If unexpected errors are found,
the file system is marked as needing a foreground check and
exits without attempting any further cleaning.
Use the block specified immediately after the flag as
the super block for the file system.
An alternate super block is usually located at block 32 for UFS1,
and block 160 for UFS2.
Check if file system was dismouted cleanly.
If so, skip file system checks (like "preen").
However, if the file system was not cleanly dismounted, do full checks,
was invoked without
Convert the file system to the specified level.
Note that the level of a file system can only be raised.
There are currently four levels defined:
The file system is in the old (static table) format.
The file system is in the new (dynamic table) format.
The file system supports 32-bit uid's and gid's,
short symbolic links are stored in the inode,
and directories have an added field showing the file type.
If maxcontig is greater than one,
build the free segment maps to aid in finding contiguous sets of blocks.
If maxcontig is equal to one, delete any existing segment maps.
In interactive mode,
will list the conversion to be made
and ask whether the conversion should be done.
If a negative answer is given,
no further operations are done on the file system.
In preen mode,
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 converted at once.
The format of a file system can be determined from the
first line of output from
in 'damaged recovery' mode, which will enable certain aggressive
operations that can make
to survive with file systems that has very serious data damage, which
is an useful last resort when on disk data damage is very serious
to crash otherwise. Be
using this flag, it is dangerous if there are data transmission hazards
because a false positive cylinder group magic number mismatch could
irrevertible data loss!
This option implies the
file systems when preening.
Use the mode specified in octal immediately after the flag as the
permission bits to use when creating the
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.
Assume a no response to all questions asked by
which is assumed to be affirmative;
do not open the file system for writing.
Preen file systems (see above).
Assume a yes response to all questions asked by
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:
Blocks claimed by more than one inode or the free map.
Blocks claimed by an inode outside the range of the file system.
Incorrect link counts.
Directory size not a multiple of DIRBLKSIZ.
Partially truncated file.
Bad inode format.
Blocks not accounted for anywhere.
File pointing to unallocated inode.
Inode number out of range.
Directories with unallocated blocks (holes).
Dot or dot-dot not the first two entries of a directory
or having the wrong inode number.
Super Block checks:
More blocks for inodes than there are in the file system.
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.
directory does not exist, it is created.
If there is insufficient space its size is increased.
contains default list of file systems to check.
The diagnostics produced by
are fully enumerated and explained in Appendix A of