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CentOS 7.0 - man page for fallocate (centos section 1)

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 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 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. -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. -p, --punch-hole 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. -h, --help Print help and exit. -V, --version Print version and exit.
Eric Sandeen <> Karel Zak <>
fallocate(2), posix_fallocate(3), truncate(1)
The fallocate command is part of the util-linux package and is available from Linux Kernel Archive < /util-linux/>. util-linux September 2011 FALLOCATE(1)