− preallocate space to a file on an NTFS volume
[options] -l length device file [attr-type
preallocates space for any attribute of a file or directory,
thus reserving space before actual contents is written. This
is similar to fallocate(1).
Below is a
summary of all the options that ntfsfallocate
accepts. Nearly all options have two equivalent names. The
short name is preceded by − and the long name
is preceded by −−. Any single letter
options, that don’t take an argument, can be combined
into a single command, e.g. −fv is equivalent
to −f −v. Long named options can be
abbreviated to any unique prefix of their name.
This will override some
sensible defaults, such as not using a mounted volume. Use
this option with caution.
Show a list of options with a
brief description of each one.
This is a mandatory option to
specify the number of bytes to preallocate. It will be
rounded up to a multiple of the cluster size. A suffix of K,
M, G, T, P or E may be appended to mean a multiplicative
factor of a power of 1000. Similarly a suffix of Ki, Mi, Gi,
Ti, Pi or Ei may be appended to mean a multiplicative factor
of a power of 1024.
Do not change the apparent size
of the file. The space allocated beyond the apparent size is
not zeroed, but subsequent writing beyond the apparent end
of file will force zeroing the inner allocated space as it
cannot be considered as a hole any more, and this may take
Simulate the allocation without
actually write to device.
Specify the offset in the file
where preallocation starts. By default, the preallocation is
counted from the beginning of the file. Space already
allocated in the area defined by offset and length is
Show the version number,
copyright and license of ntfsfallocate.
Define a particular attribute
type to be preallocated (advanced use only). By default, the
unnamed $DATA attribute (the contents of a plain file) will
be preallocated. The attribute has to be specified by a
number in decimal or hexadecimal :
Define the name of the
particular attribute type to be preallocated (advanced use
100MB to the file database.db located in the Data directory
which is at the root of an NTFS file system.
-l 100M /dev/sda1 Data/database.db
There are no
known problems with ntfsfallocate, however it can
lead to configurations not supported by Windows and Windows
may crash (BSOD) when writing to preallocated clusters which
were not written to earlier. Files with preallocated space
should be fully be written to before they are updated by
If you find a
bug in ntfsfallocate proper, please send an email
describing the problem to the development team:
was written by Jean-Pierre Andre.
is part of the ntfs-3g package and is available from: