sys-utils/fstrim.8

   1 .TH FSTRIM 8 "July 2014" "util-linux" "System Administration"
   2 .SH NAME
   3 fstrim \- discard unused blocks on a mounted filesystem
   4 .SH SYNOPSIS
   5 .B fstrim
   6 .RB [ \-a ]
   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, \-\-all\fP"
  50 Trim all mounted filesystems on devices that support the discard operation.
  51 The other supplied options, like \fB\-\-offset\fR, \fB\-\-length\fR and
  52 \fB-\-minimum\fR, are applied to all these devices.
  53 Errors from filesystems that do not support the discard operation are silently
  54 ignored.
  55 .IP "\fB\-o, \-\-offset\fP \fIoffset\fP"
  56 Byte offset in the filesystem from which to begin searching for free blocks
  57 to discard.  The default value is zero, starting at the beginning of the
  58 filesystem.
  59 .IP "\fB\-l, \-\-length\fP \fIlength\fP"
  60 The number of bytes (after the starting point) to search for free blocks
  61 to discard.  If the specified value extends past the end of the filesystem,
  62 .B fstrim
  63 will stop at the filesystem size boundary.  The default value extends to
  64 the end of the filesystem.
  65 .IP "\fB\-m, \-\-minimum\fP \fIminimum-size\fP"
  66 Minimum contiguous free range to discard, in bytes. (This value is internally
  67 rounded up to a multiple of the filesystem block size.)  Free ranges smaller
  68 than this will be ignored.  By increasing this value, the fstrim operation
  69 will complete more quickly for filesystems with badly fragmented freespace,
  70 although not all blocks will be discarded.  The default value is zero,
  71 discarding every free block.
  72 .IP "\fB\-v, \-\-verbose\fP"
  73 Verbose execution.  With this option
  74 .B fstrim
  75 will output the number of bytes passed from the filesystem
  76 down the block stack to the device for potential discard.  This number is a
  77 maximum discard amount from the storage device's perspective, because
  78 .I FITRIM
  79 ioctl called repeated will keep sending the same sectors for discard repeatedly.
  80 .sp
  81 .B fstrim
  82 will report the same potential discard bytes each time, but only sectors which
  83 had been written to between the discards would actually be discarded by the
  84 storage device.  Further, the kernel block layer reserves the right to adjust
  85 the discard ranges to fit raid stripe geometry, non-trim capable devices in a
  86 LVM setup, etc.  These reductions would not be reflected in fstrim_range.len
  87 (the
  88 .B --length
  89 option).
  90 .TP
  91 .BR \-V , " \-\-version"
  92 Display version information and exit.
  93 .TP
  94 .BR \-h , " \-\-help"
  95 Display help text and exit.
  96
  97 .SH RETURN CODES
  98 .IP 0
  99 success
 100 .IP 1
 101 failure
 102 .IP 32
 103 all failed
 104 .IP 64
 105 some filesystem discards have succeeded, some failed
 106 .PP
 107 The command
 108 .B fstrim --all
 109 returns 0 (all succeeded), 32 (all failed) or 64 (some failed, some succeeded).
 110
 111 .SH AUTHOR
 112 .nf
 113 Lukas Czerner <lczerner@redhat.com>
 114 Karel Zak <kzak@redhat.com>
 115 .fi
 116 .SH SEE ALSO
 117 .BR blkdiscard (8),
 118 .BR mount (8)
 119 .SH AVAILABILITY
 120 The fstrim command is part of the util-linux package and is available from
 121 https://www.kernel.org/pub/linux/utils/util-linux/.