.\" -*- nroff -*-
.TH FALLOCATE 1 "Jul 2009" "Version 1.0"
.SH NAME
fallocate \- preallocate space to a file.
.SH SYNOPSIS
.B fallocate
.RB [ \-n ]
.RB [ \-o
.IR offset ]
.B \-l
.IR length
.I filename
.SH DESCRIPTION
.B fallocate
is used to preallocate blocks to a file.  For filesystems which support the
fallocate system call, this is done quickly by allocating blocks and marking
them as uninitialized, requiring no IO to the data blocks.  This is much faster
than creating a file by filling it with zeros.
.PP
As of the Linux Kernel v2.6.31, the fallocate system call is supported by the
btrfs, ext4, ocfs2, and xfs filesystems.
.PP
The exit code returned by
.B fallocate
is 0 on success and 1 on failure.
.PP
.SH OPTIONS
.IP "\fB\-h, \-\-help\fP"
Print help and exit.
.IP "\fB\-n, \-\-keep-size\fP"
Do not modify the apparent length of the file. This may effectively allocate
blocks past EOF, which can be removed with a truncate.
.IP "\fB\-o, \-\-offset\fP \fIoffset\fP
Specifies the beginning offset of the allocation, in bytes.  Suffixes of k, m,
g, t, p, e may be specified to denote KiB, MiB, GiB, etc.
.IP "\fB\-l, \-\-length\fP \fIlength\fP
Specifies the length of the allocation, in bytes.  Suffixes of k, m, g, t, p, e
may be specified to denote KiB, MiB, GiB, etc.
.SH AUTHORS
.nf
Eric Sandeen <sandeen@redhat.com>
Karel Zak <kzak@redhat.com>
.fi
.SH SEE ALSO
.BR fallocate (2),
.BR posix_fallocate (3),
.BR truncate (1)
.SH AVAILABILITY
The fallocate command is part of the util-linux-ng package and is available from
ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.