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.\" -*- nroff -*-
.TH FALLOCATE 1 "September 2011" "util-linux" "User Commands"
.SH NAME
fallocate \- preallocate space to a file
.SH SYNOPSIS
.B fallocate
.RB [ \-n ]
.RB [ \-p ]
.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
The \fIlength\fR and \fIoffset\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, TB, PB, EB, ZB and YB.
.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\-p, \-\-punch-hole\fP"
Punch holes in the file, the range should not exceed the length of the file.
.IP "\fB\-o, \-\-offset\fP \fIoffset\fP
Specifies the beginning offset of the allocation, in bytes.
.IP "\fB\-l, \-\-length\fP \fIlength\fP
Specifies the length of the allocation, in bytes.
.IP "\fB\-h, \-\-help\fP"
Print help and exit.
.IP "\fB-V, \-\-version"
Print version and exit.
.SH AUTHORS
.UR sandeen@redhat.com
Eric Sandeen
.UE
.br
.UR kzak@redhat.com
Karel Zak
.UE
.SH SEE ALSO
.BR fallocate (2),
.BR posix_fallocate (3),
.BR truncate (1)
.SH AVAILABILITY
The fallocate command is part of the util-linux package and is available from
.UR ftp://\:ftp.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
Linux Kernel Archive
.UE .
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