How to NULL OUT A FILE (Linux)

Nulling is the process of resetting a file to zero bytes while at the same time not deleting it.  This is useful in cases where you want to get a file back to zero but you don't want to risk messing up permissions or file ownership.  Such as clearing a log file or a mailbox.  There are several ways to do it, each involve you having SSH access to your account. 

If you have that access goto the directory where the file is located and run this command: 

echo " " > filename
where filename is the name of the file to null. 
You should see its bytes reset to zero.