preallocate space to a file
see also :
[-n] [-o offset]
-l length filename
add an example, a script, a trick and tips
fallocate -l 512m /mnt/swap
chmod 600 /mnt/swap
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
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
length and offset arguments may be followed by
binary (2^N) suffixes 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 effectively allocate blocks
past EOF, which can be removed with a truncate.
Specifies the beginning offset
of the allocation, in bytes.
Specifies the length of the
allocation, in bytes.
The fallocate command is part of the util-linux package and is
available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
Karel Zak <kzak[:at:]redhat[:dot:]com>