85 lines
3.0 KiB
Groff
85 lines
3.0 KiB
Groff
.\" -*- nroff -*-
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.TH FSTRIM 8 "November 2010" "util-linux" "System Administration"
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.SH NAME
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fstrim \- discard unused blocks on a mounted filesystem
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.SH SYNOPSIS
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.B fstrim
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.RB [ \-o
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.IR offset ]
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.RB [ \-l
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.IR length ]
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.RB [ \-m
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.IR minimum-free-extent ]
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.RB [ \-v ]
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.I mountpoint
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.SH DESCRIPTION
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.B fstrim
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is used on a mounted filesystem to discard (or "trim") blocks which are not in
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use by the filesystem. This is useful for solid-state drives (SSDs) and
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thinly-provisioned storage.
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.PP
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By default,
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.B fstrim
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will discard all unused blocks in the filesystem. Options may be used to
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modify this behavior based on range or size, as explained below.
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.PP
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The
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.I mountpoint
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argument is the pathname of the directory where the filesystem
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is mounted.
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.SH OPTIONS
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The \fIoffset\fR, \fIlength\fR, and \fIminimum-free-extent\fR arguments may be
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followed by binary (2^N) suffixes KiB, MiB, GiB, TiB, PiB and EiB (the "iB" is
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optional, e.g. "K" has the same meaning as "KiB") or decimal (10^N) suffixes
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KB, MB, GB, PB and EB.
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.IP "\fB\-h, \-\-help\fP"
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Print help and exit.
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.IP "\fB\-o, \-\-offset\fP \fIoffset\fP"
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Byte offset in filesystem from which to begin searching for free blocks
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to discard. Default value is zero, starting at the beginning of the
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filesystem.
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.IP "\fB\-l, \-\-length\fP \fIlength\fP"
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Number of bytes after starting point to search for free blocks to discard.
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If the specified value extends past the end of the filesystem,
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.B fstrim
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will stop at the filesystem size boundary. Default value extends to the end
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of the filesystem.
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.IP "\fB\-m, \-\-minimum\fP \fIminimum-free-extent\fP"
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Minimum contiguous free range to discard, in bytes. (This value is internally
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rounded up to a multiple of the filesystem block size). Free ranges smaller
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than this will be ignored. By increasing this value, the fstrim operation
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will complete more quickly for filesystems with badly fragmented freespace,
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although not all blocks will be discarded. Default value is zero, discard
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every free block.
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.IP "\fB\-v, \-\-verbose\fP"
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Verbose execution. When specified
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.B fstrim
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will output the number of bytes passed from the filesystem
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down the block stack to the device for potential discard. This number is a
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maximum discard amount from the storage device's perspective, because
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.I FITRIM
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ioctl called repeated will keep sending the same sectors for discard repeatedly.
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.B fstrim
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will report the same potential discard bytes each time, but only sectors which
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had been written to between the discards would actually be discarded by the
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storage device. Further, the kernel block layer reserves the right to adjust
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the discard ranges to fit raid stripe geometry, non-trim capable devices in a
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LVM setup, etc. These reductions would not be reflected in fstrim_range.len
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(the
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.B --length
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option).
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.SH AUTHOR
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.nf
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Lukas Czerner <lczerner@redhat.com>
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Karel Zak <kzak@redhat.com>
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.fi
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.SH SEE ALSO
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.BR mount (8)
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.SH AVAILABILITY
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The fstrim command is part of the util-linux package and is available from
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ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
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