mkfile allows you to create files with arbitary sizes. This comes in handy if want to test file transfer speeds between two endpoints and you want use a file with an exact size.

The command below let’s you create 100M file.

$ mkfile -n 100M 100M.data

Below the is the syntax for mkfile

Syntax
          mkfile [ -nv ] size[b|k|m|g] filename ...
Options
   -n     Create an empty filename.  The size is noted,  but  disk  blocks
          aren't allocated until data is written to them.

   -v     Verbose.  Report the names and sizes of created files.