John R Pierce wrote:
the seed of a algorithm like /dev/urandom is not a single variable, its a big array of variables. these have to be created with sufficiently random external events to achieve a reasonable level of entropy, and if you continue to generate pseudo-random-numbers from this when those random external events aren't ongoing at a high enough rate relative to your requirements for new random numbers, eventually the 'entropy' runs out, and the sequence becomes increasingly predictable.
According to Wikipedia "A random seed (or seed state, or just seed) is a number (or vector) used to initialize a pseudorandom number generator."
It is impossible to measure the entropy of a single number, or vector. If you think it is, tell me how you measure it.