| .\" -*- nroff -*- |
| .TH FALLOCATE 1 "Jul 2009" "Version 1.0" |
| .SH NAME |
| fallocate \- preallocate space to a file. |
| .SH SYNOPSIS |
| .B fallocate |
| .RB [ \-n ] |
| .RB [ \-o |
| .IR offset ] |
| .B \-l |
| .IR length |
| .I filename |
| .SH DESCRIPTION |
| .B fallocate |
| 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. |
| .PP |
| As of the Linux Kernel v2.6.31, the fallocate system call is supported by the |
| btrfs, ext4, ocfs2, and xfs filesystems. |
| .PP |
| The exit code returned by |
| .B fallocate |
| is 0 on success and 1 on failure. |
| .PP |
| .SH OPTIONS |
| .IP "\fB\-h, \-\-help\fP" |
| Print help and exit. |
| .IP "\fB\-n, \-\-keep-size\fP" |
| Do not modify the apparent length of the file. This may effectively allocate |
| blocks past EOF, which can be removed with a truncate. |
| .IP "\fB\-o, \-\-offset\fP \fIoffset\fP |
| Specifies the beginning offset of the allocation, in bytes. Suffixes of k, m, |
| g, t, p, e may be specified to denote KiB, MiB, GiB, etc. |
| .IP "\fB\-l, \-\-length\fP \fIlength\fP |
| Specifies the length of the allocation, in bytes. Suffixes of k, m, g, t, p, e |
| may be specified to denote KiB, MiB, GiB, etc. |
| .SH AUTHORS |
| .nf |
| Eric Sandeen <sandeen@redhat.com> |
| Karel Zak <kzak@redhat.com> |
| .fi |
| .SH SEE ALSO |
| .BR fallocate (2), |
| .BR posix_fallocate (3), |
| .BR truncate (1) |
| .SH AVAILABILITY |
| The fallocate command is part of the util-linux-ng package and is available from |
| ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/. |
| |
