# fsck

## NAME



           fsck - check and repair a Linux filesystem
    


## SYNOPSIS



           **fsck**[**-lsAVRTMNP**] [**-r**[_fd_]] [**-C**[_fd_]] [**-t** _fstype_] [_filesystem_...]
           [**--**] [_fs-specific-options_]
    


## DESCRIPTION



           **fsck** is used to check and optionally repair one or more Linux
           filesystems. _filesystem_ can be a device name (e.g., _/dev/hdc1_ ,
           _/dev/sdb2_), a mount point (e.g., _/_ , _/usr_ , _/home_), or a filesystem
           label or UUID specifier (e.g.,
           UUID=8868abf6-88c5-4a83-98b8-bfc24057f7bd or LABEL=root).
           Normally, the **fsck** program will try to handle filesystems on
           different physical disk drives in parallel to reduce the total
           amount of time needed to check all of them.
    
           If no filesystems are specified on the command line, and the **-A**
           option is not specified, **fsck** will default to checking filesystems
           in _/etc/fstab_ serially. This is equivalent to the **-As** options.
    
           The exit status returned by **fsck** is the sum of the following
           conditions:
    
           **0**
               No errors
    
           **1**
               Filesystem errors corrected
    
           **2**
               System should be rebooted
    
           **4**
               Filesystem errors left uncorrected
    
           **8**
               Operational error
    
           **16**
               Usage or syntax error
    
           **32**
               Checking canceled by user request
    
           **128**
               Shared-library error
    
           The exit status returned when multiple filesystems are checked is
           the bit-wise OR of the exit statuses for each filesystem that is
           checked.
    
           In actuality, **fsck** is simply a front-end for the various
           filesystem checkers (**fsck**._fstype_) available under Linux. The
           filesystem-specific checker is searched for in the **PATH**
           environment variable. If the **PATH** is undefined then fallback to
           _/sbin_.
    
           Please see the filesystem-specific checker manual pages for
           further details.
    


## OPTIONS



           **-l**
               Create an exclusive flock(2) lock file
               (_/run/fsck/ <diskname>.lock_) for whole-disk device. This option
               can be used with one device only (this means that **-A** and **-l**
               are mutually exclusive). This option is recommended when more
               **fsck** instances are executed in the same time. The option is
               ignored when used for multiple devices or for non-rotating
               disks. **fsck** does not lock underlying devices when executed to
               check stacked devices (e.g. MD or DM) - this feature is not
               implemented yet.
    
           **-r**[_fd_]
               Report certain statistics for each fsck when it completes.
               These statistics include the exit status, the maximum run set
               size (in kilobytes), the elapsed all-clock time and the user
               and system CPU time used by the fsck run. For example:
    
               **/dev/sda1: status 0, rss 92828, real 4.002804, user 2.677592,**
               **sys 0.86186**
    
               GUI front-ends may specify a file descriptor _fd_ , in which case
               the progress bar information will be sent to that file
               descriptor in a machine parsable format. For example:
    
               **/dev/sda1 0 92828 4.002804 2.677592 0.86186**
    
           **-s**
               Serialize **fsck** operations. This is a good idea if you are
               checking multiple filesystems and the checkers are in an
               interactive mode. (Note: e2fsck(8) runs in an interactive mode
               by default. To make e2fsck(8) run in a non-interactive mode,
               you must either specify the **-p** or **-a** option, if you wish for
               errors to be corrected automatically, or the **-n** option if you
               do not.)
    
           **-t** _fslist_
               Specifies the type(s) of filesystem to be checked. When the **-A**
               flag is specified, only filesystems that match _fslist_ are
               checked. The _fslist_ parameter is a comma-separated list of
               filesystems and options specifiers. All of the filesystems in
               this comma-separated list may be prefixed by a negation
               operator '**no** ' or '**!** ', which requests that only those
               filesystems not listed in _fslist_ will be checked. If none of
               the filesystems in _fslist_ is prefixed by a negation operator,
               then only those listed filesystems will be checked.
    
               Options specifiers may be included in the comma-separated
               _fslist_. They must have the format **opts=**_fs-option_. If an
               options specifier is present, then only filesystems which
               contain _fs-option_ in their mount options field of _/etc/fstab_
               will be checked. If the options specifier is prefixed by a
               negation operator, then only those filesystems that do not
               have _fs-option_ in their mount options field of _/etc/fstab_ will
               be checked.
    
               For example, if **opts=ro** appears in _fslist_ , then only
               filesystems listed in _/etc/fstab_ with the **ro** option will be
               checked.
    
               For compatibility with Mandrake distributions whose boot
               scripts depend upon an unauthorized UI change to the **fsck**
               program, if a filesystem type of **loop** is found in _fslist_ , it
               is treated as if **opts=loop** were specified as an argument to
               the **-t** option.
    
               Normally, the filesystem type is deduced by searching for
               _filesys_ in the _/etc/fstab_ file and using the corresponding
               entry. If the type cannot be deduced, and there is only a
               single filesystem given as an argument to the **-t** option, **fsck**
               will use the specified filesystem type. If this type is not
               available, then the default filesystem type (currently ext2)
               is used.
    
           **-A**
               Walk through the _/etc/fstab_ file and try to check all
               filesystems in one run. This option is typically used from the
               _/etc/rc_ system initialization file, instead of multiple
               commands for checking a single filesystem.
    
               The root filesystem will be checked first unless the **-P** option
               is specified (see below). After that, filesystems will be
               checked in the order specified by the _fs_passno_ (the sixth)
               field in the _/etc/fstab_ file. Filesystems with a _fs_passno_
               value of 0 are skipped and are not checked at all. Filesystems
               with a _fs_passno_ value of greater than zero will be checked in
               order, with filesystems with the lowest _fs_passno_ number being
               checked first. If there are multiple filesystems with the same
               pass number, **fsck** will attempt to check them in parallel,
               although it will avoid running multiple filesystem checks on
               the same physical disk.
    
               **fsck** does not check stacked devices (RAIDs, dm-crypt, ...) in
               parallel with any other device. See below for
               **FSCK_FORCE_ALL_PARALLEL** setting. The _/sys_ filesystem is used
               to determine dependencies between devices.
    
               Hence, a very common configuration in _/etc/fstab_ files is to
               set the root filesystem to have a _fs_passno_ value of 1 and to
               set all other filesystems to have a _fs_passno_ value of 2. This
               will allow **fsck** to automatically run filesystem checkers in
               parallel if it is advantageous to do so. System administrators
               might choose not to use this configuration if they need to
               avoid multiple filesystem checks running in parallel for some
               reason - for example, if the machine in question is short on
               memory so that excessive paging is a concern.
    
               **fsck** normally does not check whether the device actually
               exists before calling a filesystem specific checker. Therefore
               non-existing devices may cause the system to enter filesystem
               repair mode during boot if the filesystem specific checker
               returns a fatal error. The _/etc/fstab_ mount option **nofail** may
               be used to have **fsck** skip non-existing devices. **fsck** also
               skips non-existing devices that have the special filesystem
               type **auto**.
    
           **-C**[_fd_]
               Display completion/progress bars for those filesystem checkers
               (currently only for ext[234]) which support them. **fsck** will
               manage the filesystem checkers so that only one of them will
               display a progress bar at a time. GUI front-ends may specify a
               file descriptor _fd_ , in which case the progress bar information
               will be sent to that file descriptor.
    
           **-M**
               Do not check mounted filesystems and return an exit status of
               0 for mounted filesystems.
    
           **-N**
               Don’t execute, just show what would be done.
    
           **-P**
               When the **-A** flag is set, check the root filesystem in parallel
               with the other filesystems. This is not the safest thing in
               the world to do, since if the root filesystem is in doubt
               things like the e2fsck(8) executable might be corrupted! This
               option is mainly provided for those sysadmins who don’t want
               to repartition the root filesystem to be small and compact
               (which is really the right solution).
    
           **-R**
               When checking all filesystems with the **-A** flag, skip the root
               filesystem. (This is useful in case the root filesystem has
               already been mounted read-write.)
    
           **-T**
               Don’t show the title on startup.
    
           **-V**
               Produce verbose output, including all filesystem-specific
               commands that are executed.
    
           **-?** , **--help**
               Display help text and exit.
    
           **--version**
               Display version and exit.
    


## FILESYSTEM SPECIFIC OPTIONS



           **Options which are not understood by fsck are passed to the**
           **filesystem-specific checker!**
    
           These options **must** not take arguments, as there is no way for **fsck**
           to be able to properly guess which options take arguments and
           which don’t.
    
           Options and arguments which follow the **--** are treated as
           filesystem-specific options to be passed to the
           filesystem-specific checker.
    
           Please note that **fsck** is not designed to pass arbitrarily
           complicated options to filesystem-specific checkers. If you’re
           doing something complicated, please just execute the
           filesystem-specific checker directly. If you pass **fsck** some
           horribly complicated options and arguments, and it doesn’t do what
           you expect, **don’t bother reporting it as a bug.** You’re almost
           certainly doing something that you shouldn’t be doing with **fsck**.
           Options to different filesystem-specific fsck’s are not
           standardized.
    


## ENVIRONMENT



           The **fsck** program’s behavior is affected by the following
           environment variables:
    
           **FSCK_FORCE_ALL_PARALLEL**
               If this environment variable is set, **fsck** will attempt to
               check all of the specified filesystems in parallel, regardless
               of whether the filesystems appear to be on the same device.
               (This is useful for RAID systems or high-end storage systems
               such as those sold by companies such as IBM or EMC.) Note that
               the _fs_passno_ value is still used.
    
           **FSCK_MAX_INST**
               This environment variable will limit the maximum number of
               filesystem checkers that can be running at one time. This
               allows configurations which have a large number of disks to
               avoid **fsck** starting too many filesystem checkers at once,
               which might overload CPU and memory resources available on the
               system. If this value is zero, then an unlimited number of
               processes can be spawned. This is currently the default, but
               future versions of **fsck** may attempt to automatically determine
               how many filesystem checks can be run based on gathering
               accounting data from the operating system.
    
           **PATH**
               The **PATH** environment variable is used to find filesystem
               checkers.
    
           **FSTAB_FILE**
               This environment variable allows the system administrator to
               override the standard location of the _/etc/fstab_ file. It is
               also useful for developers who are testing **fsck**.
    
           **LIBBLKID_DEBUG=all**
               enables libblkid debug output.
    
           **LIBMOUNT_DEBUG=all**
               enables libmount debug output.
    


## FILES



           _/etc/fstab_
    


## NOTES



           During boot, **systemd** does not invoke **fsck -A**. Instead, it
           schedules the activation of mounts individually, taking into
           account dependencies on backing devices, networking, and other
           factors. Consequently, **fsck** is called individually for each
           device.
    


## AVAILABILITY



           The **fsck** command is part of the util-linux package which can be
           downloaded from Linux Kernel Archive
           <https://www.kernel.org/pub/linux/utils/util-linux/>. This page is
           part of the _util-linux_ (a random collection of Linux utilities)
           project. Information about the project can be found at 
           ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a
           bug report for this manual page, send it to
           util-linux@vger.kernel.org. This page was obtained from the
           project's upstream Git repository
           ⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
           2025-08-11. (At that time, the date of the most recent commit that
           was found in the repository was 2025-08-05.) If you discover any
           rendering problems in this HTML version of the page, or you
           believe there is a better or more up-to-date source for the page,
           or you have corrections or improvements to the information in this
           COLOPHON (which is _not_ part of the original manual page), send a
           mail to man-pages@man7.org
    
    util-linux 2.42-start-521-ec46  2025-08-09                        _FSCK_(8)
    


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