fallocate [-n] [-o offset] -l length filename
fallocate is used to preallocate blocks to a file. For filesystems
which support the fallocate system call, this is done quickly by allo-
cating blocks and marking them as uninitialized, requiring no IO to the
data blocks. This is much faster than creating a file by filling it
As of the Linux Kernel v2.6.31, the fallocate system call is supported
by the btrfs, ext4, ocfs2, and xfs filesystems.
The exit code returned by fallocate is 0 on success and 1 on failure.
The length and offset arguments may be followed by binary (2^N) suf-
fixes KiB, MiB, GiB, TiB, PiB and EiB (the "iB" is optional, e.g. "K"
has the same meaning as "KiB") or decimal (10^N) suffixes KB, MB, GB,
PB and EB.
Print help and exit.
Do not modify the apparent length of the file. This may effec-
tively allocate blocks past EOF, which can be removed with a
-o, --offset offset
Specifies the beginning offset of the allocation, in bytes.
-l, --length length
Specifies the length of the allocation, in bytes.
Eric Sandeen <firstname.lastname@example.org>
Karel Zak <email@example.com>
fallocate(2), posix_fallocate(3), truncate(1)
The fallocate command is part of the util-linux package and is avail-
able from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
util-linux July 2009 FALLOCATE(1)
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