Entropy

On modern Linux kernels (5.10+) entropy_avail will normally return 256 (bits), which tells you that you can get a 256-bit random number from /dev/[u]random, and that it will probably take, on average, 2^255 guesses to crack it.

A read from the /dev/urandom device will not block waiting for more entropy. As a result, if there is not sufficient entropy in the entropy pool, the returned values are theoretically vulnerable to a cryptographic attack on the algorithms used by the driver. If this is a concern in your application, use /dev/random instead. https://linux.die.net/man/4/random

• Get current entropy level

cat /proc/sys/kernel/random/entropy_avail

• Improve entropy level

apt-get install rng-tools
rngd -r /dev/urandom