FALLOCATE(1) User Commands FALLOCATE(1)
fallocate - preallocate space to a file
fallocate [-n] [-p] [-o offset] -l length filename
fallocate is used to preallocate blocks to a file. For filesystems which support the fal-
locate system call, this is done quickly by allocating blocks and marking them as unini-
tialized, 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 fallocate is 0 on success and 1 on failure.
The length and offset 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.
Do not modify the apparent length of the file. This may effectively allocate
blocks past EOF, which can be removed with a truncate.
Punch holes in the file, the range should not exceed the length of the file.
-o, --offset offset
Specifies the beginning offset of the allocation, in bytes.
-l, --length length
Specifies the length of the allocation, in bytes.
Print help and exit.
Print version and exit.
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 available from Linux Kernel
util-linux September 2011 FALLOCATE(1)