In a GNU/Linux distributions, there are special files 
(/dev/random and /dev/urandom) to access the kernel’s random number generator.

- /dev/urandom device returns random bytes using a pseudoran‐
   dom number generator seeded from the entropy pool. 
   
- /dev/random  device  is a legacy interface which dates back to a time
   where  the  cryptographic  primitives  used  in  the   implementation   of
   /dev/urandom  were  not  widely trusted.