sys-utils/blkdiscard.8

   1 .TH BLKDISCARD 8 "July 2014" "util-linux" "System Administration"
   2 .SH NAME
   3 blkdiscard \- discard sectors on a device
   4 .SH SYNOPSIS
   5 .B blkdiscard
   6 [options]
   7 .RB [ \-o
   8 .IR offset ]
   9 .RB [ \-l
  10 .IR length ]
  11 .I device
  12 .SH DESCRIPTION
  13 .B blkdiscard
  14 is used to discard device sectors.  This is useful for solid-state
  15 drivers (SSDs) and thinly-provisioned storage.  Unlike
  16 .BR fstrim (8),
  17 this command is used directly on the block device.
  18 .PP
  19 By default,
  20 .B blkdiscard
  21 will discard all blocks on the device.  Options may be used to modify
  22 this behavior based on range or size, as explained below.
  23 .PP
  24 The
  25 .I device
  26 argument is the pathname of the block device.
  27 .PP
  28 .B WARNING: All data in the discarded region on the device will be lost!
  29 .SH OPTIONS
  30 The
  31 .I offset
  32 and
  33 .I length
  34 arguments may be followed by the multiplicative suffixes KiB (=1024),
  35 MiB (=1024*1024), and so on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is
  36 optional, e.g., "K" has the same meaning as "KiB") or the suffixes
  37 KB (=1000), MB (=1000*1000), and so on for GB, TB, PB, EB, ZB and YB.
  38 .TP
  39 .BR \-f , " \-\-force"
  40 Disable all checking.  Since v2.36 the block device is open in exclusive mode (O_EXCL)
  41 by default to avoid collision with mounted filesystem or another kernel subsystem.
  42 The force option disables the exclusive access mode.
  43 .TP
  44 .BR \-o , " \-\-offset \fIoffset"
  45 Byte offset into the device from which to start discarding.  The provided value
  46 will be aligned to the device sector size.  The default value is zero.
  47 .TP
  48 .BR \-l , " \-\-length \fIlength"
  49 The number of bytes to discard (counting from the starting point).  The provided value
  50 will be aligned to the device sector size.  If the specified value extends past
  51 the end of the device,
  52 .B blkdiscard
  53 will stop at the device size boundary.  The default value extends to the end
  54 of the device.
  55 .TP
  56 .BR \-p , " \-\-step \fIlength"
  57 The number of bytes to discard within one iteration. The default is to discard
  58 all by one ioctl call.
  59 .TP
  60 .BR \-s , " \-\-secure"
  61 Perform a secure discard.  A secure discard is the same as a regular discard
  62 except that all copies of the discarded blocks that were possibly created by
  63 garbage collection must also be erased.  This requires support from the device.
  64 .TP
  65 .BR \-z , " \-\-zeroout"
  66 Zero-fill rather than discard.
  67 .TP
  68 .BR \-v , " \-\-verbose"
  69 Display the aligned values of
  70 .I offset
  71 and
  72 .IR length .
  73 If the \fB\-\-step\fR option is specified, it prints the discard progress every second.
  74 .TP
  75 .BR \-V , " \-\-version"
  76 Display version information and exit.
  77 .TP
  78 .BR \-h , " \-\-help"
  79 Display help text and exit.
  80 .SH AUTHOR
  81 .MT lczerner@redhat.com
  82 Lukas Czerner
  83 .ME
  84 .SH SEE ALSO
  85 .BR fstrim (8)
  86 .SH AVAILABILITY
  87 The blkdiscard command is part of the util-linux package and is available
  88 .UR https://\:www.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
  89 Linux Kernel Archive
  90 .UE .