sys-utils/fstrim.8

   1 .\" -*- nroff -*-
   2 .TH FSTRIM 8 "July 2014" "util-linux" "System Administration"
   3 .SH NAME
   4 fstrim \- discard unused blocks on a mounted filesystem
   5 .SH SYNOPSIS
   6 .B fstrim
   7 .RB [ \-a ]
   8 .RB [ \-o
   9 .IR offset ]
  10 .RB [ \-l
  11 .IR length ]
  12 .RB [ \-m
  13 .IR minimum-size ]
  14 .RB [ \-v ]
  15 .I mountpoint
  16
  17 .SH DESCRIPTION
  18 .B fstrim
  19 is used on a mounted filesystem to discard (or "trim") blocks which are not in
  20 use by the filesystem.  This is useful for solid-state drives (SSDs) and
  21 thinly-provisioned storage.
  22 .PP
  23 By default,
  24 .B fstrim
  25 will discard all unused blocks in the filesystem.  Options may be used to
  26 modify this behavior based on range or size, as explained below.
  27 .PP
  28 The
  29 .I mountpoint
  30 argument is the pathname of the directory where the filesystem
  31 is mounted.
  32 .PP
  33 Running
  34 .B fstrim
  35 frequently, or even using
  36 .BR "mount -o discard" ,
  37 might negatively affect the lifetime of poor-quality SSD devices.  For most
  38 desktop and server systems the sufficient trimming frequency is once a week.
  39 Note that not all
  40 devices support a queued trim, so each trim command incurs a performance penalty
  41 on whatever else might be trying to use the disk at the time.
  42
  43 .SH OPTIONS
  44 The \fIoffset\fR, \fIlength\fR, and \fIminimum-size\fR arguments may be
  45 followed by the multiplicative suffixes KiB (=1024),
  46 MiB (=1024*1024), and so on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB"
  47 is optional, e.g., "K" has the same meaning as "KiB") or the suffixes
  48 KB (=1000), MB (=1000*1000), and so on for GB, TB, PB, EB, ZB and YB.
  49
  50 .IP "\fB\-a, \-\-all\fP"
  51 Trim all mounted filesystems on devices that support the discard operation.
  52 The other supplied options, like \fB\-\-offset\fR, \fB\-\-length\fR and
  53 \fB-\-minimum\fR, are applied to all these devices.
  54 Errors from filesystems that do not support the discard operation are silently
  55 ignored.
  56 .IP "\fB\-o, \-\-offset\fP \fIoffset\fP"
  57 Byte offset in the filesystem from which to begin searching for free blocks
  58 to discard.  The default value is zero, starting at the beginning of the
  59 filesystem.
  60 .IP "\fB\-l, \-\-length\fP \fIlength\fP"
  61 The number of bytes (after the starting point) to search for free blocks
  62 to discard.  If the specified value extends past the end of the filesystem,
  63 .B fstrim
  64 will stop at the filesystem size boundary.  The default value extends to
  65 the end of the filesystem.
  66 .IP "\fB\-m, \-\-minimum\fP \fIminimum-size\fP"
  67 Minimum contiguous free range to discard, in bytes. (This value is internally
  68 rounded up to a multiple of the filesystem block size).  Free ranges smaller
  69 than this will be ignored.  By increasing this value, the fstrim operation
  70 will complete more quickly for filesystems with badly fragmented freespace,
  71 although not all blocks will be discarded.  Default value is zero, discard
  72 every free block.
  73 .IP "\fB\-v, \-\-verbose\fP"
  74 Verbose execution.  With this option
  75 .B fstrim
  76 will output the number of bytes passed from the filesystem
  77 down the block stack to the device for potential discard.  This number is a
  78 maximum discard amount from the storage device's perspective, because
  79 .I FITRIM
  80 ioctl called repeated will keep sending the same sectors for discard repeatedly.
  81 .sp
  82 .B fstrim
  83 will report the same potential discard bytes each time, but only sectors which
  84 had been written to between the discards would actually be discarded by the
  85 storage device.  Further, the kernel block layer reserves the right to adjust
  86 the discard ranges to fit raid stripe geometry, non-trim capable devices in a
  87 LVM setup, etc.  These reductions would not be reflected in fstrim_range.len
  88 (the
  89 .B --length
  90 option).
  91 .TP
  92 .BR \-V , " \-\-version"
  93 Display version information and exit.
  94 .TP
  95 .BR \-h , " \-\-help"
  96 Display help text and exit.
  97
  98 .SH RETURN CODES
  99 .IP 0
 100 success
 101 .IP 1
 102 failure
 103 .IP 32
 104 all failed
 105 .IP 64
 106 some filesystem discards have succeeded, some failed
 107 .PP
 108 The command
 109 .B fstrim --all
 110 returns 0 (all succeeded), 32 (all failed) or 64 (some failed, some succeeded).
 111
 112 .SH AUTHOR
 113 .nf
 114 Lukas Czerner <lczerner@redhat.com>
 115 Karel Zak <kzak@redhat.com>
 116 .fi
 117 .SH SEE ALSO
 118 .BR mount (8)
 119 .SH AVAILABILITY
 120 The fstrim command is part of the util-linux package and is available from
 121 ftp://ftp.kernel.org/pub/linux/utils/util-linux/.