Software install directories are standard, and, unless you really know what you are doing, you should not attempt to change this. (HINT: If you ask this question, you don't know.)
Program executables are always installed in /bin, /sbin, /usr/bin, /usr/sbin, /usr/local/bin and /usr/local/sbin. There is no good reason for changing this. They are only ~100mb. Also, there is no way to change the install directory when you use packages. However, you won't ever fill 20GB with programs. The executables and libraries are ~1gb, not more.
The rest is data, and goes in several places under /usr and /var. All configuration goes in /etc (with the exception of user-specific settings, which go in /home/<username>). Your files are in /home/<username>.
Have a look at:
http://www.comptechdoc.org/os/linux/...ilestruct.html
http://www.tuxfiles.org/linuxhelp/linuxdir.html
You will have to partition your slave and mount partitions to where you need the most space. Please post the output of:
Code:
mount
df -h
cd /; du -hcs *
cd /usr; du -hcs *
This will show where you need space.