Linux Kernel Random Number Entropy

The Linux Kernel uses “entropy” to generate random numbers:

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

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

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

This 256 seems to have recently changed.

Older blog posts state that 256 available entropy is too low.

I doubt that on modern 2022 Kernels, such as a 5.17 from Fedora 34 or a 5.18 in Fedora 36, this is still accurate. It now actually remains at 256 forever, even with keyboard and mouse and disk events; even a restart does not budge it.

References

• https://wiki.archlinux.org/title/Rng-tools
• https://blog.pcfe.net/hugo/posts/2011-11-04-tpm-to-feed-random-number-generator/
• https://github.com/jirka-h/haveged, note the IMPORTANT UPDATE
• https://wiki.alpinelinux.org/wiki/Entropy_and_randomness
• https://wiki.qemu.org/Features/VirtIORNG
• https://fedoraproject.org/wiki/Features/Virtio_RNG
• https://wiki.archlinux.org/title/Random_number_generation