Mac Developer Library Developer


This manual page is for Mac OS X version 10.9

If you are running a different version of Mac OS X, view the documentation locally:

  • In Terminal, using the man(1) command

Reading manual pages

Manual pages are intended as a quick reference for people who already understand a technology.

  • To learn how the manual is organized or to learn about command syntax, read the manual page for manpages(5).

  • For more information about this technology, look for other documentation in the Apple Developer Library.

  • For general information about writing shell scripts, read Shell Scripting Primer.

FSCK(8)                   BSD 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 nor-mally normally
     mally 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_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 cor-rected corrected
     rected inconsistency one or more lines will be printed identifying the filesystem on which the correc-tion correction
     tion 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.

     -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 cau-tion caution
                 tion as this is a free license to continue after essentially unlimited trouble has been

     -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_msdos(8), getfsent(3), reboot(8)

4th Berkeley Distribution        May 18, 2010        4th Berkeley Distribution

Reporting Problems

The way to report a problem with this manual page depends on the type of problem:

Content errors
Report errors in the content of this documentation with the feedback links below.
Bug reports
Report bugs in the functionality of the described tool or API through Bug Reporter.
Formatting problems
Report formatting mistakes in the online version of these pages with the feedback links below.