This post is not meant to be a sure method for defeating attackers. That you can make the process so tedious and time consuming for the attacker, that he will likely not bother and move to another victim. This post is about those methods.
STEP ONE: Prepare your hard drive.
The goal of this step is to install an encrypted filesystem. So, before we do that, we need to do some preparation. In order to get to that point, you will need to write random or pseudorandom data to the entire disk. This will take some time. My experience has show that laptop drives usually operate around 30MBps, so if you have a 300GB drive, this will take you just under 3 hours. The reason for doing this is to confuse the attacker just exactly where the encrypted filesystems reside. If the entire disk is underlined with random or pseudorandom data (it doesn’t necessarily need to be cryptographically secure here), then when looking at the drive level, it will be practically improbable to determine where the encrypted filesystem starts and where it ends. If you skip this step, then it’s quite obvious, and rather than wast his time on the entire disk, the attacker can focus his efforts on just the obvious encrypted portions of the disk.
rest here