The OP is somewhat mistaken about entropy sources within a modern system.
A modern OS implementation keeps a record of the number of shannons of entropy available in the /dev/random pool and only allows that amount to be taken out.
The /dev/urandom pool simply allows the user to continue removing bits of data when there are no shannons of entropy left in the pool.
The only way to acquire more shannons of entropy to fill the /dev/random pool (and hence provide a way for /dev/urandom pool to also acquire more) is to have a physical source of truly random nature.
Such sources can include the timing information of key presses which introduce fractions of a shannon of entropy but network activity of any type is disturbingly periodic, hence such sources have largely been removed.
If you want a true random number generator you need something like an Entropy key which uses physical quantum phenomena to generate many shannons of entropy continuously.

Hi all, it appears someone has slashdotted my bookshelf. Hope you got something useful from it :-)

A quick note that the original idea behind this was to assist some of our customers in the embedded arena by showing what books we used. Yes there are a number of "classics" missing (they were mostly on the shelf below ;-) but the idea was for a representative "sample" not a definitive booklist. If I were to create such a list it would include at least

• The Pragmatic Programmer by hunt
• Code Complete by McConnell
• Engineering mathmatics by K A Stroud

• A history of modern computing by Ceruzzi
• The code book by Simon Singh (actually almost anything by Singh)
• The victorian Internet by Tom Standage

Some people have noted they dont use their knuth much, personally I would often be lost without it, although there are many other good books on practical algorithms out there now (I am and old fart and years ago knuth was *it* ;-)