Sparse File Creation

[Steven Chervets]

I need to create an 8 GB sized sparse file which will do an actual  
block allocation.  In other words, I want to allocate the blocks in  
the directory structure, but not fill them with zeroes until they are  
actually used.  Since this will be implemented in a closed appliance  
I'm not concerned about security and can execute any command as root.

I have tried the dd seek command.  And while it creates a sparse file,  
it doesn't reserve the blocks.

Thank you for your help.

Steve