FSTRIM(8) - phpMan

FSTRIM(8) System Administration FSTRIM(8)

NAME
fstrim - discard unused blocks on a mounted filesystem

SYNOPSIS
fstrim [-Aa] [-o offset] [-l length] [-m minimum-size] [-v 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.

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 and read-only filesystems are
silently ignored.

-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.

-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.

-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 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.

-V, --version
Display version information and exit.

-h, --help
Display help text 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).

AUTHORS
Lukas Czerner <lczerner AT redhat.com>, Karel Zak <kzak AT redhat.com>