sys-utils/fstrim.8

   1 .TH FSTRIM 8 "May 2019" "util-linux" "System Administration"
   2 .SH NAME
   3 fstrim \- discard unused blocks on a mounted filesystem
   4 .SH SYNOPSIS
   5 .B fstrim
   6 .RB [ \-Aa ]
   7 .RB [ \-o
   8 .IR offset ]
   9 .RB [ \-l
  10 .IR length ]
  11 .RB [ \-m
  12 .IR minimum-size ]
  13 .RB [ \-v ]
  14 .I mountpoint
  15
  16 .SH DESCRIPTION
  17 .B fstrim
  18 is used on a mounted filesystem to discard (or "trim") blocks which are not in
  19 use by the filesystem.  This is useful for solid-state drives (SSDs) and
  20 thinly-provisioned storage.
  21 .PP
  22 By default,
  23 .B fstrim
  24 will discard all unused blocks in the filesystem.  Options may be used to
  25 modify this behavior based on range or size, as explained below.
  26 .PP
  27 The
  28 .I mountpoint
  29 argument is the pathname of the directory where the filesystem
  30 is mounted.
  31 .PP
  32 Running
  33 .B fstrim
  34 frequently, or even using
  35 .BR "mount \-o discard" ,
  36 might negatively affect the lifetime of poor-quality SSD devices.  For most
  37 desktop and server systems a sufficient trimming frequency is once a week.
  38 Note that not all
  39 devices support a queued trim, so each trim command incurs a performance penalty
  40 on whatever else might be trying to use the disk at the time.
  41
  42 .SH OPTIONS
  43 The \fIoffset\fR, \fIlength\fR, and \fIminimum-size\fR arguments may be
  44 followed by the multiplicative suffixes KiB (=1024),
  45 MiB (=1024*1024), and so on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB"
  46 is optional, e.g., "K" has the same meaning as "KiB") or the suffixes
  47 KB (=1000), MB (=1000*1000), and so on for GB, TB, PB, EB, ZB and YB.
  48
  49 .IP "\fB\-A, \-\-fstab\fP"
  50 Trim all mounted filesystems mentioned in \fI/etc/fstab\fR on devices that support the
  51 discard operation.  The root filesystem is determined from kernel command line if missing
  52 in the file.
  53 The other supplied options, like \fB\-\-offset\fR, \fB\-\-length\fR and
  54 \fB-\-minimum\fR, are applied to all these devices.
  55 Errors from filesystems that do not support the discard operation,
  56 read-only devices and read-only filesystems are silently ignored.
  57 .IP "\fB\-a, \-\-all\fP"
  58 Trim all mounted filesystems on devices that support the discard operation.
  59 The other supplied options, like \fB\-\-offset\fR, \fB\-\-length\fR and
  60 \fB-\-minimum\fR, are applied to all these devices.
  61 Errors from filesystems that do not support the discard operation,
  62 read-only devices and read-only filesystems are silently ignored.
  63 .IP "\fB\-n, \-\-dry\-run\fP"
  64 This option does everything apart from actually call FITRIM ioctl.
  65 .IP "\fB\-o, \-\-offset\fP \fIoffset\fP"
  66 Byte offset in the filesystem from which to begin searching for free blocks
  67 to discard.  The default value is zero, starting at the beginning of the
  68 filesystem.
  69 .IP "\fB\-l, \-\-length\fP \fIlength\fP"
  70 The number of bytes (after the starting point) to search for free blocks
  71 to discard.  If the specified value extends past the end of the filesystem,
  72 .B fstrim
  73 will stop at the filesystem size boundary.  The default value extends to
  74 the end of the filesystem.
  75 .IP "\fB\-m, \-\-minimum\fP \fIminimum-size\fP"
  76 Minimum contiguous free range to discard, in bytes. (This value is internally
  77 rounded up to a multiple of the filesystem block size.)  Free ranges smaller
  78 than this will be ignored and fstrim will adjust the minimum if it's smaller than
  79 the device's minimum, and report that (fstrim_range.minlen) back to userspace.
  80 By increasing this value, the fstrim operation will complete more quickly for
  81 filesystems with badly fragmented freespace, although not all blocks will be
  82 discarded.  The default value is zero, discarding every free block.
  83 .IP "\fB\-v, \-\-verbose\fP"
  84 Verbose execution.  With this option
  85 .B fstrim
  86 will output the number of bytes passed from the filesystem
  87 down the block stack to the device for potential discard.  This number is a
  88 maximum discard amount from the storage device's perspective, because
  89 .I FITRIM
  90 ioctl called repeated will keep sending the same sectors for discard repeatedly.
  91 .sp
  92 .B fstrim
  93 will report the same potential discard bytes each time, but only sectors which
  94 had been written to between the discards would actually be discarded by the
  95 storage device.  Further, the kernel block layer reserves the right to adjust
  96 the discard ranges to fit raid stripe geometry, non-trim capable devices in a
  97 LVM setup, etc.  These reductions would not be reflected in fstrim_range.len
  98 (the
  99 .B \-\-length
 100 option).
 101 .TP
 102 .B \-\-quiet\-unsupported
 103 Suppress error messages if trim operation (ioctl) is unsupported.  This option
 104 is meant to be used in systemd service file or in cron scripts to hide warnings
 105 that are result of known problems,
 106 such as NTFS driver
 107 reporting
 108 .I Bad file descriptor
 109 when device is mounted read-only, or lack of file system support for ioctl
 110 FITRIM call.
 111 .TP
 112 .BR \-V , " \-\-version"
 113 Display version information and exit.
 114 .TP
 115 .BR \-h , " \-\-help"
 116 Display help text and exit.
 117
 118 .SH EXIT STATUS
 119 .IP 0
 120 success
 121 .IP 1
 122 failure
 123 .IP 32
 124 all failed
 125 .IP 64
 126 some filesystem discards have succeeded, some failed
 127 .PP
 128 The command
 129 .B fstrim \-\-all
 130 returns 0 (all succeeded), 32 (all failed) or 64 (some failed, some succeeded).
 131
 132 .SH AUTHORS
 133 .nf
 134 Lukas Czerner <lczerner@redhat.com>
 135 Karel Zak <kzak@redhat.com>
 136 .fi
 137 .SH SEE ALSO
 138 .BR blkdiscard (8),
 139 .BR mount (8)
 140 .SH AVAILABILITY
 141 The fstrim command is part of the util-linux package and is available from
 142 https://www.kernel.org/pub/linux/utils/util-linux/.