Entropy in the Linux Kernel

Entropy is required to generate random numbers. /dev/random and /dev/urandom on Linux provide a way to access random numbers. Both devices are supplied by the kernel's PRNG, though /dev/random will block when the entropy pool is depleted while /dev/urandom will continue to generate random numbers.

Entropy Pools

You can see the size of the entropy pool size in linux by running:

cat /proc/sys/kernel/random/poolsize

The number of 'bits' of entropy can be seen at:

cat /proc/sys/kernel/random/entropy_avail

See Also

• http://www.2uo.de/myths-about-urandom/