NAME
fsck —
filesystem consistency check and
interactive repair
SYNOPSIS
fsck |
-p [-f] |
fsck |
[-l maxparallel]
[-q] [-y]
[-n] [-d] |
DESCRIPTION
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 cleanly.
-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
fsckexcept 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.
SEE ALSO
fs(5), fsck_hfs(8), fsck_apfs(8), fsck_msdos(8), getfsent(3), fstab(5,) reboot(8)