Section: User Commands (1)
Updated: July 2009
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fallocate - preallocate space to a file
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.
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
is 0 on success and 1 on failure.
The 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.
- -h, --help
Print help and exit.
- -n, --keep-size
Do not modify the apparent length of the file. This may effectively allocate
blocks past EOF, which can be removed with a truncate.
- -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 <email@example.com>
Karel Zak <firstname.lastname@example.org>
The fallocate command is part of the util-linux package and is available from
- SEE ALSO
This document was created by
using the manual pages.
Time: 11:39:22 GMT, January 18, 2018