1FSTRIM(8) System Administration FSTRIM(8)
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6 fstrim - discard unused blocks on a mounted filesystem
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9 fstrim [-a] [-o offset] [-l length] [-m minimum-size] [-v] mountpoint
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13 fstrim is used on a mounted filesystem to discard (or "trim") blocks
14 which are not in use by the filesystem. This is useful for solid-state
15 drives (SSDs) and thinly-provisioned storage.
16 By default, fstrim will discard all unused blocks in the filesystem.
18 Options may be used to modify this behavior based on range or size, as
19 explained below.
20 The mountpoint argument is the pathname of the directory where the
22 filesystem is mounted.
23 Running fstrim frequently, or even using mount -o discard, might nega‐
25 tively affect the lifetime of poor-quality SSD devices. For most desk‐
26 top and server systems a sufficient trimming frequency is once a week.
27 Note that not all devices support a queued trim, so each trim command
28 incurs a performance penalty on whatever else might be trying to use
29 the disk at the time.
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33 The offset, length, and minimum-size arguments may be followed by the
34 multiplicative suffixes KiB (=1024), MiB (=1024*1024), and so on for
35 GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is optional, e.g., "K" has
36 the same meaning as "KiB") or the suffixes KB (=1000), MB (=1000*1000),
37 and so on for GB, TB, PB, EB, ZB and YB.
38 -a, --all
41 Trim all mounted filesystems on devices that support the discard
42 operation. The other supplied options, like --offset, --length
43 and --minimum, are applied to all these devices. Errors from
44 filesystems that do not support the discard operation are
45 silently ignored.
46 -o, --offset offset
48 Byte offset in the filesystem from which to begin searching for
49 free blocks to discard. The default value is zero, starting at
50 the beginning of the filesystem.
51 -l, --length length
53 The number of bytes (after the starting point) to search for
54 free blocks to discard. If the specified value extends past the
55 end of the filesystem, fstrim will stop at the filesystem size
56 boundary. The default value extends to the end of the filesys‐
57 tem.
58 -m, --minimum minimum-size
60 Minimum contiguous free range to discard, in bytes. (This value
61 is internally rounded up to a multiple of the filesystem block
62 size.) Free ranges smaller than this will be ignored. By
63 increasing this value, the fstrim operation will complete more
64 quickly for filesystems with badly fragmented freespace,
65 although not all blocks will be discarded. The default value is
66 zero, discarding every free block.
67 -v, --verbose
69 Verbose execution. With this option fstrim will output the num‐
70 ber of bytes passed from the filesystem down the block stack to
71 the device for potential discard. This number is a maximum dis‐
72 card amount from the storage device's perspective, because
73 FITRIM ioctl called repeated will keep sending the same sectors
74 for discard repeatedly.
75 fstrim will report the same potential discard bytes each time,
77 but only sectors which had been written to between the discards
78 would actually be discarded by the storage device. Further, the
79 kernel block layer reserves the right to adjust the discard
80 ranges to fit raid stripe geometry, non-trim capable devices in
81 a LVM setup, etc. These reductions would not be reflected in
82 fstrim_range.len (the --length option).
83 -V, --version
85 Display version information and exit.
86 -h, --help
88 Display help text and exit.
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92 0 success
93 1 failure
95 32 all failed
97 64 some filesystem discards have succeeded, some failed
99 The command fstrim --all returns 0 (all succeeded), 32 (all failed) or
101 64 (some failed, some succeeded).
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105 Lukas Czerner <lczerner@redhat.com>
106 Karel Zak <kzak@redhat.com>
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109 blkdiscard(8), mount(8)
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112 The fstrim command is part of the util-linux package and is available
113 from https://www.kernel.org/pub/linux/utils/util-linux/.
114util-linux July 2014 FSTRIM(8)