53 lines
1.6 KiB
Groff
53 lines
1.6 KiB
Groff
.\" -*- nroff -*-
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.TH FALLOCATE 1 "Jul 2009" "Version 1.0"
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.SH NAME
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fallocate \- preallocate space to a file.
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.SH SYNOPSIS
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.B fallocate
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.RB [ \-n ]
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.RB [ \-o
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.IR offset ]
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.B \-l
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.IR length
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.I filename
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.SH DESCRIPTION
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.B fallocate
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is used to preallocate blocks to a file. For filesystems which support the
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fallocate system call, this is done quickly by allocating blocks and marking
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them as uninitialized, requiring no IO to the data blocks. This is much faster
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than creating a file by filling it with zeros.
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.PP
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As of the Linux Kernel v2.6.31, the fallocate system call is supported by the
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btrfs, ext4, ocfs2, and xfs filesystems.
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.PP
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The exit code returned by
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.B fallocate
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is 0 on success and 1 on failure.
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.PP
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.SH OPTIONS
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The \fIlength\fR and \fIoffset\fR arguments may be followed by binary (2^N)
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suffixes KiB, MiB, GiB, TiB, PiB and EiB (the "iB" is optional, e.g. "K" has the
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same meaning as "KiB") or decimal (10^N) suffixes 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\-n, \-\-keep-size\fP"
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Do not modify the apparent length of the file. This may effectively allocate
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blocks past EOF, which can be removed with a truncate.
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.IP "\fB\-o, \-\-offset\fP \fIoffset\fP
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Specifies the beginning offset of the allocation, in bytes.
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.IP "\fB\-l, \-\-length\fP \fIlength\fP
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Specifies the length of the allocation, in bytes.
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.SH AUTHORS
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.nf
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Eric Sandeen <sandeen@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 fallocate (2),
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.BR posix_fallocate (3),
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.BR truncate (1)
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.SH AVAILABILITY
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The fallocate command is part of the util-linux-ng package and is available from
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ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.
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