maintaining ydl health

[Kevin McMahon]

how do I use the terminal to maintain a healthy ydl 4.0. In os x there
are certain apps that fix permissions, empty caches etc, what are they
in ydl?
for instance I use the command 'sudo periodic weekly' to run maintenance
on the os and I use disk utility to fix permissions and an app called
'cocktail' to empty caches and tmp files... I want to do this because my
partition for ydl is filling up fast and I have no idea why and I think
i need to run some maintenance via the terminal.
Also how do I run the 'fsck'(sp) command to check for the integrity
etc...