# fstrim

## NAME



           fstrim - discard unused blocks on a mounted filesystem
    


## SYNOPSIS



           **fstrim**[**-v**] [**-o** _offset_] [**-l** _length_] [**-m** _minimum-size_]
           **-A** |**-a** |_mountpoint_
    


## DESCRIPTION



           **fstrim** is used on a mounted filesystem to discard (or "trim")
           blocks which are not in use by the filesystem. This is useful for
           solid-state drives (SSDs) and thinly-provisioned storage.
    
           By default, **fstrim** will discard all unused blocks in the
           filesystem. Options may be used to modify this behavior based on
           range or size, as explained below.
    
           The _mountpoint_ argument is the pathname of the directory where the
           filesystem is mounted and is required when _-A, -a, --fstab, or_
           _--all are unspecified._
    
           _Running_ **fstrim** _frequently, or even using_ **mount -o discard** _, might_
           _negatively affect the lifetime of poor-quality SSD devices. For_
           _most desktop and server systems a sufficient trimming frequency is_
           _once a week. Note that not all devices support a queued trim, so_
           _each trim command incurs a performance penalty on whatever else_
           _might be trying to use the disk at the time._
    


## OPTIONS



           The _offset_ , _length_ , and _minimum-size_ arguments may be followed by
           the multiplicative suffixes KiB (=1024), MiB (=1024*1024), and so
           on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is optional,
           e.g., "K" has the same meaning as "KiB") or the suffixes KB
           (=1000), MB (=1000*1000), and so on for GB, TB, PB, EB, ZB and YB.
    
           **-A, --fstab**
               Trim all mounted filesystems mentioned in _/etc/fstab_ on
               devices that support the discard operation. The root
               filesystem is determined from kernel command line if missing
               in the file. The other supplied options, like **--offset** ,
               **--length** and **--minimum** , are applied to all these devices.
               Errors from filesystems that do not support the discard
               operation, read-only devices, autofs and read-only filesystems
               are silently ignored. Filesystems with "X-fstrim.notrim" mount
               option are skipped.
    
           **-a, --all**
               Trim all mounted filesystems on devices that support the
               discard operation. The other supplied options, like **--offset** ,
               **--length** and **--minimum** , are applied to all these devices.
               Errors from filesystems that do not support the discard
               operation, read-only devices and read-only filesystems are
               silently ignored.
    
           **-n, --dry-run**
               This option does everything apart from actually call **FITRIM**
               ioctl.
    
           **-o, --offset** _offset_
               Byte offset in the filesystem from which to begin searching
               for free blocks to discard. The default value is zero,
               starting at the beginning of the filesystem.
    
           **-l, --length** _length_
               The number of bytes (after the starting point) to search for
               free blocks to discard. If the specified value extends past
               the end of the filesystem, **fstrim** will stop at the filesystem
               size boundary. The default value extends to the end of the
               filesystem.
    
           **-I, --listed-in** _list_
               Specifies a colon-separated list of files in fstab or kernel
               mountinfo format. All missing or empty files are silently
               ignored. The evaluation of the _list_ stops after first
               non-empty file. For example:
    
               **--listed-in /etc/fstab:/proc/self/mountinfo**.
    
               Filesystems with "X-fstrim.notrim" mount option in fstab are
               skipped.
    
           **-m, --minimum** _minimum-size_
               Minimum contiguous free range to discard, in bytes. (This
               value is internally rounded up to a multiple of the filesystem
               block size.) Free ranges smaller than this will be ignored and
               **fstrim** will adjust the minimum if it’s smaller than the
               device’s minimum, and report that (fstrim_range.minlen) back
               to userspace. By increasing this value, the **fstrim** operation
               will complete more quickly for filesystems with badly
               fragmented freespace, although not all blocks will be
               discarded. The default value is zero, discarding every free
               block.
    
           **-t** , **--types** _list_
               Specifies allowed or forbidden filesystem types when used with
               **--all** or **--fstab**. The _list_ is a comma-separated list of the
               filesystem names. The _list_ follows how **mount -t** evaluates type
               patterns. Only specified filesystem types are allowed. All
               specified types are forbidden if the list is prefixed by "no"
               or each filesystem prefixed by "no" is forbidden. If the
               option is not used, then all filesystems (except "autofs") are
               allowed.
    
           **-v, --verbose**
               Verbose execution. With this option **fstrim** will output the
               number of bytes passed from the filesystem down the block
               stack to the device for potential discard. This number is a
               maximum discard amount from the storage device’s perspective,
               because _FITRIM_ ioctl called repeated will keep sending the
               same sectors for discard repeatedly.
    
               **fstrim** will report the same potential discard bytes each time,
               but only sectors which had been written to between the
               discards would actually be discarded by the storage device.
               Further, the kernel block layer reserves the right to adjust
               the discard ranges to fit raid stripe geometry, non-trim
               capable devices in a LVM setup, etc. These reductions would
               not be reflected in fstrim_range.len (the **--length** option).
    
           **--quiet-unsupported**
               Suppress error messages if trim operation (ioctl) is
               unsupported. This option is meant to be used in **systemd**
               service file or in cron(8) scripts to hide warnings that are
               result of known problems, such as NTFS driver reporting _Bad_
               _file descriptor_ when device is mounted read-only, or lack of
               file system support for ioctl _FITRIM_ call. This option also
               cleans exit status when unsupported filesystem specified on
               **fstrim** command line.
    
           **-h** , **--help**
               Display help text and exit.
    
           **-V** , **--version**
               Display version and exit.
    


## EXIT STATUS



           0
               success
    
           1
               failure
    
           32
               all failed
    
           64
               some filesystem discards have succeeded, some failed
    
           The command **fstrim --all** returns 0 (all succeeded), 32 (all
           failed) or 64 (some failed, some succeeded).
    


## AVAILABILITY



           The **fstrim** 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  2025-01-16                      _FSTRIM_(8)
    


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