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.\" -*- nroff -*-
.TH BLKDISCARD 8 "September 2012" "util-linux" "System Administration"
.SH NAME
blkdiscard \- discard sectors on a device
.SH SYNOPSIS
.B blkdiscard
.RB [ \-o
.IR offset ]
.RB [ \-l
.IR length ]
.RB [ \-s ]
.RB [ \-v ]
.I device
.SH DESCRIPTION
.B blkdiscard
is used to discard device sectors. This is useful for solid-state
drivers (SSDs) and thinly-provisioned storage. Unlike
.BR fstrim (8)
this command is used directly on the block device.
.PP
By default,
.B blkdiscard
will discard all blocks on the device. Options may be used to
modify this behavior based on range or size, as explained below.
.PP
The
.I device
argument is the pathname of the block device.
.B WARNING: All data in the discarded region on the device will be lost!
.SH OPTIONS
The \fIoffset\fR and \fIlength\fR arguments may be
followed by the multiplicative suffixes KiB=1024, MiB=1024*1024, and so on for
GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is optional, e.g. "K" has the same
meaning as "KiB") or the suffixes KB=1000, MB=1000*1000, and so on for GB, PB,
EB, ZB and YB.
.IP "\fB\-h, \-\-help\fP"
Print help and exit.
.IP "\fB\-o, \-\-offset\fP \fIoffset\fP"
Byte offset in the device from which to discard. Provided value will be
aligned to the device sector size. Default value is zero.
.IP "\fB\-l, \-\-length\fP \fIlength\fP"
Number of bytes after starting point to discard. Provided value will be
aligned to the device sector size. If the specified value extends past the
end of the device,
.B blkdiscard
will stop at the device size boundary. Default value extends to the end
of the device.
.IP "\fB\-s, \-\-secure\fP"
Perform secure discard. Secure discard is the same as regular discard except
all copies of the discarded blocks possibly created by garbage collection must
also be erased. It has to be supported by the device.
.IP "\fB\-v, \-\-verbose\fP"
Print aligned \fIoffset\fR and \fIlength\fR arguments.
.SH AUTHOR
.nf
Lukas Czerner <lczerner@redhat.com>
.fi
.SH SEE ALSO
.BR fstrim (8)
.SH AVAILABILITY
The blkdiscard command is part of the util-linux package and is available
from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
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