> This is easy question, how do i defrag the disk?

You don't. :-)

"Fragmentation" on an FFS is not the same thing as on a MacOS or
MS-DOS disk. I know a number of computers where we've never bothered.

If you ever need to clean things up, the best way is to copy all the files
off, delete it, and copy them back. But like I said, I doubt it's
necessary.

Take care,

Bill