Er... permissions are changed by
'chmod', 'chown', 'chgrp' usually. The man pages on them are rather straightforward. 'top' is a good one to see your current memory/swap usage. 'dmesg' shows the output of the kernel's hardware recognition log.
Honestly man, for all the command-line commands, aside from the man pages, you might want to pick up O'Reilly's Linux in a Nutshell, which is little more than a big dictionary of everything you could enter in the command line with definitions that explain things usually far better than the man pages.