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 [-Aa] [-o offset] [-l length] [-m minimum-size] [-v mountpoint]
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12 fstrim is used on a mounted filesystem to discard (or "trim") blocks
13 which are not in use by the filesystem. This is useful for solid-state
14 drives (SSDs) and thinly-provisioned storage.
15 By default, fstrim will discard all unused blocks in the filesystem.
17 Options may be used to modify this behavior based on range or size, as
18 explained below.
19 The mountpoint argument is the pathname of the directory where the
21 filesystem is mounted.
22 Running fstrim frequently, or even using mount -o discard, might
24 negatively affect the lifetime of poor-quality SSD devices. For most
25 desktop and server systems a sufficient trimming frequency is once a
26 week. Note that not all devices support a queued trim, so each trim
27 command incurs a performance penalty on whatever else might be trying
28 to use the disk at the time.
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31 The offset, length, and minimum-size arguments may be followed by the
32 multiplicative suffixes KiB (=1024), MiB (=1024*1024), and so on for
33 GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is optional, e.g., "K" has
34 the same meaning as "KiB") or the suffixes KB (=1000), MB (=1000*1000),
35 and so on for GB, TB, PB, EB, ZB and YB.
36 -A, --fstab
38 Trim all mounted filesystems mentioned in /etc/fstab on devices
39 that support the discard operation. The root filesystem is
40 determined from kernel command line if missing in the file. The
41 other supplied options, like --offset, --length and --minimum, are
42 applied to all these devices. Errors from filesystems that do not
43 support the discard operation, read-only devices, autofs and
44 read-only filesystems are silently ignored. Filesystems with
45 "X-fstrim.notrim" mount option are skipped.
46 -a, --all
48 Trim all mounted filesystems on devices that support the discard
49 operation. The other supplied options, like --offset, --length and
50 --minimum, are applied to all these devices. Errors from
51 filesystems that do not support the discard operation, read-only
52 devices and read-only filesystems are silently ignored.
53 -n, --dry-run
55 This option does everything apart from actually call FITRIM ioctl.
56 -o, --offset offset
58 Byte offset in the filesystem from which to begin searching for
59 free blocks to discard. The default value is zero, starting at the
60 beginning of the filesystem.
61 -l, --length length
63 The number of bytes (after the starting point) to search for free
64 blocks to discard. If the specified value extends past the end of
65 the filesystem, fstrim will stop at the filesystem size boundary.
66 The default value extends to the end of the filesystem.
67 -I, --listed-in list
69 Specifies a colon-separated list of files in fstab or kernel
70 mountinfo format. All missing or empty files are silently ignored.
71 The evaluation of the list stops after first non-empty file. For
72 example:
73 --listed-in /etc/fstab:/proc/self/mountinfo.
75 Filesystems with "X-fstrim.notrim" mount option in fstab are
77 skipped.
78 -m, --minimum minimum-size
80 Minimum contiguous free range to discard, in bytes. (This value is
81 internally rounded up to a multiple of the filesystem block size.)
82 Free ranges smaller than this will be ignored and fstrim will
83 adjust the minimum if it’s smaller than the device’s minimum, and
84 report that (fstrim_range.minlen) back to userspace. By increasing
85 this value, the fstrim operation will complete more quickly for
86 filesystems with badly fragmented freespace, although not all
87 blocks will be discarded. The default value is zero, discarding
88 every free block.
89 -v, --verbose
91 Verbose execution. With this option fstrim will output the number
92 of bytes passed from the filesystem down the block stack to the
93 device for potential discard. This number is a maximum discard
94 amount from the storage device’s perspective, because FITRIM ioctl
95 called repeated will keep sending the same sectors for discard
96 repeatedly.
97 fstrim will report the same potential discard bytes each time, but
99 only sectors which had been written to between the discards would
100 actually be discarded by the storage device. Further, the kernel
101 block layer reserves the right to adjust the discard ranges to fit
102 raid stripe geometry, non-trim capable devices in a LVM setup, etc.
103 These reductions would not be reflected in fstrim_range.len (the
104 --length option).
105 --quiet-unsupported
107 Suppress error messages if trim operation (ioctl) is unsupported.
108 This option is meant to be used in systemd service file or in
109 cron(8) scripts to hide warnings that are result of known problems,
110 such as NTFS driver reporting Bad file descriptor when device is
111 mounted read-only, or lack of file system support for ioctl FITRIM
112 call. This option also cleans exit status when unsupported
113 filesystem specified on fstrim command line.
114 -h, --help
116 Display help text and exit.
117 -V, --version
119 Print version and exit.
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122 0
123 success
124 1
126 failure
127 32
129 all failed
130 64
132 some filesystem discards have succeeded, some failed
133 The command fstrim --all returns 0 (all succeeded), 32 (all failed) or
135 64 (some failed, some succeeded).
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138 Lukas Czerner <lczerner@redhat.com>, Karel Zak <kzak@redhat.com>
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141 blkdiscard(8), mount(8)
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144 For bug reports, use the issue tracker at
145 https://github.com/util-linux/util-linux/issues.
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148 The fstrim command is part of the util-linux package which can be
149 downloaded from Linux Kernel Archive
150 <https://www.kernel.org/pub/linux/utils/util-linux/>.
151util-linux 2.38.1 2022-05-11 FSTRIM(8)