FSCK_FFS(8) BSD System Manager's Manual FSCK_FFS(8)
fsck_ffs - Fast Filesystem consistency check and interactive repair
fsck_ffs [-fnpy] [-b block#] [-c level] [-m mode] filesystem ...
fsck_ffs performs interactive filesystem consistency checks and repairs
for each filesystem 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_ffs with the -p option will
correct; if it encounters other inconsistencies, it exits with an abnor-
mal return status and an automatic reboot will then fail. For each
corrected inconsistency, one or more lines will be printed identifying
the filesystem on which the correction will take place along with the na-
ture of the correction. After successfully correcting a filesystem,
fsck_ffs will print the number of files on that filesystem, the number of
used and free blocks, and the percentage of fragmentation.
If sent a QUIT signal, fsck_ffs will finish the filesystem checks, then
exit with an abnormal return status that causes an automatic reboot to
fail. This is useful when you want to finish the filesystem checks during
an automatic reboot, but do not want the machine to come up multiuser
after the checks complete.
If sent an INFO signal, fsck_ffs will print a line to standard error in-
dicating the name of the device currently being checked, the current
phase number, and phase-specific progress information.
Without the -p option, fsck_ffs audits and interactively repairs incon-
sistent 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_ffs 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_ffs:
-b block#
Use the block# specified as the super block for the filesystem.
Block 32 is usually an alternate super block.
-c level
Convert the filesystem to the specified level. Note that the lev-
el of a filesystem can only be raised. There are currently four
levels defined:
0 The filesystem is in the old (static table) format.
1 The filesystem is in the new (dynamic table) format.
2 The filesystem supports 32-bit UIDs and GIDs, short sym-
bolic links are stored in the inode, and directories have
an added field showing the file type.
3 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.
-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_ffs will not check the filesystem.
This option forces fsck_ffs to check the filesystem, regardless
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
1700. In particular, systems that wish to have lost files acces-
sible by all users on the system should use a less restrictive
set of permissions such as 755.
-n Assume a "no" response to all questions asked by fsck_ffs except
for "CONTINUE?", which is assumed to be affirmative. Filesystems
will not be opened for writing. This is the default for filesys-
tems to be checked that are concurrently mounted writable.
-y Assume a "yes" response to all questions asked by fsck_ffs; this
should be used with great caution as this is a free license to
continue after essentially unlimited trouble has been encoun-
tered.
In interactive mode, fsck_ffs 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 filesystem. In preen mode, the conver-
sion is listed and done if possible without user interaction. Conversion
in preen mode is best used when all the filesystems are being converted
at once. The format of a filesystem can be determined from the first line
of output from dumpfs(8).
If no filesystems are given to fsck_ffs then a default list of filesys-
tems is read from the file /etc/fstab.
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 DIRBLKSIZ.
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_ffs are fully enumerated and explained
in Appendix A of fsck_ffs - The UNIX(R) Filesystem Check Program.
fs(5), fstab(5), fsck(8), fsdb(8), growfs(8), mount_ffs(8), newfs(8),
rc(8)
Marshall Kirk McKusick, fsck_ffs - The UNIX(R) Filesystem Check Program,
03.fsck_ffs(SMM).
MirBSD #10-current November 29, 1994 2