FSCK(8) System Manager's Manual FSCK(8)
fsck – filesystem consistency check and interactive repair
fsck -p [-f]
fsck [-l maxparallel] [-q] [-y] [-n] [-d]
The first form of fsck preens a standard set of filesystems or the
specified filesystems. It is normally used in the script /etc/rc during
automatic reboot. Here fsck reads the filesystem descriptor table (using
getfsent(3)) to determine which filesystems to check. Only partitions that
have ``rw,'' ``rq'' or ``ro'' as options, 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 shortest prefix
of the device name that ends in one or more digits; the remaining
characters are assumed to be the partition designator. In preening mode,
filesystems that are marked clean are skipped. Filesystems are marked
clean when they are unmounted, when they have been mounted read-only, or
when fsck runs on them successfully.
It should be noted that fsck is now essentially a wrapper that invokes
other fsck_XXX utilities as needed. Currently, fsck can invoke fsck_hfs,
fsck_apfs, fsck_msdos, fsck_exfat, and fsck_udf. If this underlying
process that fsck invokes encounters serious inconsistencies or the
filesystem type is not one of the above, 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 filesystem
on which the correction will take place, and the nature of the correction.
If sent a QUIT signal, fsck 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.
Without the -p option, fsck audits and interactively repairs inconsistent
conditions for filesystems. 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. If the operator does not have write permission on
the filesystem fsck will default to a -n action.
The following flags are interpreted by fsck and passed along to the
underlying tool that it spawns.
-f Force fsck to check `clean' filesystems when preening.
-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.
-R Specify a particular passno number for which fsck is to check. You
may only specify 1 or 2. Only those filesystems matching that
particular passno entry (if using fstab) will be checked. For more
information on the passno field, see fstab(5).
-p "Preen" mode, described above.
-q Do a quick check to determine if the filesystem was unmounted
-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
filesystem for writing.
If no filesystems are given to fsck then a default list of filesystems is
read using getfsent(3).
Because of inconsistencies between the block device and the buffer cache,
the raw device should always be used.
fs(5), fsck_hfs(8), fsck_apfs(8), fsck_msdos(8), getfsent(3), fstab(5,)
BSD 4 May 18, 2010 BSD 4