Oracle Linux: CRNG Entropy Value in Oracle Linux with UEKr5 Update 5 or UEKr6 Update 2 and later

Applies to

Linux OS - Version Oracle Linux 7.9 with Unbreakable Enterprise Kernel [5.4.17] and later

Linux x86-64

Goal

When using UEKr5 Update 5 ( 4.14.35-2047.517.1.el7uek ) or UEKr6 Update 2 ( kernel-uek-5.4.17-2102 and higher ), /proc/sys/kernel/random/entropy_avail shows a static value

$ cat /proc/sys/kernel/random/entropy_avail
256

Even when running rngd and/or changing parameters like kernel.random.write_wakeup_threshold

Solution

The parameter /proc/sys/kernel/random/entropy_avail can be ignored since UEKr5 Update 5 or UEKr6 Update 2 as the kernel now uses CSPRNG (Cryptographically Secure PseudoRandom Number Generator).

For more information the block post from Linux Kernel Development: