What is Kernel Entropy Pool?
The kernel entropy pool is a mechanism that the Linux kernel uses to generate random numbers. At the time of registering an interrupt handler for a device, you can specify whether interrupts from this device contribute to the "entropy". Try google and here it pops: Linux implements a purely algorithmic random number generator, accessible as /dev/urandom. Its results are good enough for most purposes, but there are times when true randomness is needed. To that end, the kernel attempts to harvest randomness (called "entropy") from its environment. The timing between the keystrokes as your editor types this article, for example, exhibits some randomness. The same is true of, for example, the timing of disk interrupts. The lower bits of the system time stamp counter can also provide a bit of entropy. The kernel collects this entropy into a special pool of bits, and uses this entropy pool when true random numbers (obtained from /dev/random) are required. The amount of accumulated entropy is also tracked; if there is insufficient entropy in the pool to satisfy a random number request, the requesting process will block until the needed entropy arrives. One of the most common ways of putting entropy into the pool is to register interrupt handlers with the SA_SAMPLE_RANDOM flag. That flag tells the kernel that the indicated interrupt will arrive at random times, so its timing can be used to generate entropy Rajat -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
