FSCK(8) Maintenance Commands and Procedures FSCK(8)


fsck - check and repair file systems


fsck [-F FSType] [-m] [-V] [-v] [special]...

fsck [-F FSType] [-n | N | y | Y] [-V] [-v]
[-o FSType-specific-options] [special]...


fsck audits and interactively repairs inconsistent file system
conditions. If the file system is inconsistent the default action for
each correction is to wait for the user to respond yes or no. If the user
does not have write permission fsck defaults to a no action. Some
corrective actions will result in loss of data. The amount and severity
of data loss can be determined from the diagnostic output.

FSType-specific-options are options specified in a comma-separated (with
no intervening spaces) list of options or keyword-attribute pairs for
interpretation by the FSType-specific module of the command.

special represents the character special device on which the file system
resides, for example, /dev/rdsk/c1t0d0s7. Note: the character special
device, not the block special device, should be used. fsck will not work
if the block device is mounted.

If no special device is specified fsck checks the file systems listed in
/etc/vfstab. Those entries in /etc/vfstab which have a character special
device entry in the fsckdev field and have a non-zero numeric entry in
the fsckpass field will be checked. Specifying -F FSType limits the file
systems to be checked to those of the type indicated.

If special is specified, but -F is not, the file system type will be
determined by looking for a matching entry in /etc/vfstab. If no entry is
found, the default local file system type specified in /etc/default/fs
will be used.

If a file system type supports parallel checking, for example, ufs, some
file systems eligible for checking may be checked in parallel. Consult
the file system-specific man page (for example, fsck_ufs(8)) for more


The following generic options are supported:

-F FSType

Specify the file system type on which to operate.


Check but do not repair. This option checks that the file system is
suitable for mounting, returning the appropriate exit status. If the
file system is ready for mounting, fsck displays a message such as:

ufs fsck: sanity check: /dev/rdsk/c0t3d0s1 okay

-n | -N

Assume a no response to all questions asked by fsck; do not open the
file system for writing.


Echo the expanded command line but do not execute the command. This
option may be used to verify and to validate the command line.


Enables verbose output. Might not be supported by all filesystem-
specific fsck implementations.

-y | Y

Assume a yes response to all questions asked by fsck.

-o specific-options

These specific-options can be any combination of the following
separated by commas (with no intervening spaces).


Use block n as the super block for the file system. Block 32 is
always one of the alternate super blocks. Determine the location
of other super blocks by running newfs(8) with the -Nv options


If the file system is in the old (static table) format, convert
it to the new (dynamic table) format. If the file system is in
the new format, convert it to the old format provided the old
format can support the file system configuration. In interactive
mode, fsck will list the direction the conversion is to be made
and ask whether the conversion should be done. If a negative
answer is given, no further operations are done on the file
system. In preen mode, the direction of the conversion is listed
and done if possible without user interaction. Conversion in
preen mode is best used when all the file systems are being
converted at once. The format of a file system can be determined
from the first line of output from fstyp(8). Note: the c option
is seldom used and is included only for compatibility with
pre-4.1 releases. There is no guarantee that this option will be
included in future releases.


Force checking of file systems regardless of the state of their
super block clean flag.


Check and fix the file system non-interactively ("preen"). Exit
immediately if there is a problem requiring intervention. This
option is required to enable parallel file system checking.


Check writable file systems only.



file system is unmounted and OK


erroneous parameters are specified


file system is unmounted and needs checking (fsck -m only)


file system is already mounted


cannot stat device


a filesystem that is mounted read/write was modified - reboot


uncorrectable errors detected - terminate normally


a signal was caught during processing


uncorrectable errors detected - terminate immediately


file system is mounted read-only and is OK


The fsck command is large file aware for UFS file systems, per the
largefile(7) man page.



default local file system type. Default values can be set for the
following flags in /etc/default/fs. For example: LOCAL=ufs.


The default partition for a command if no FSType is specified.


list of default parameters for each file system


See attributes(7) for descriptions of the following attributes:

|Interface Stability | Committed |


ufs(4FS), vfstab(5), attributes(7), largefile(7), clri(8), fsck_ufs(8),
fsdb_ufs(8), fsirand(8), fstyp(8), mkfs(8), mkfs_ufs(8), mountall(8),
newfs(8), reboot(8)


The operating system buffers file system data. Running fsck on a mounted
file system can cause the operating system's buffers to become out of
date with respect to the disk. For this reason, the file system should be
unmounted when fsck is used. If this is not possible, care should be
taken that the system is quiescent and that it is rebooted immediately
after fsck is run. Quite often, however, this will not be sufficient. A
panic will probably occur if running fsck on a file system modifies the
file system.


This command may not be supported for all FSTypes.

Starting with Solaris 9, fsck manages extended attribute data on the
disk. (See fsattr(7) for a description of extended file attributes.) A
file system with extended attributes can be mounted on versions of
Solaris that are not attribute-aware (versions prior to Solaris 9), but
the attributes will not be accessible and fsck will strip them from the
files and place them in lost+found. Once the attributes have been
stripped, the file system is completely stable on versions of Solaris
that are not attribute-aware, but would be considered corrupted on
attribute-aware versions. In the latter circumstance, run the attribute-
aware fsck to stabilize the file system before using it in an attribute-
aware environment.

September 8, 2015 FSCK(8)