Solaris
/dev/random and /dev/urandom have been available as Sun packages or patches for Solaris since Solaris 2.6, and have been a standard feature since Solaris 9. As of Solaris 10, administrators can remove existing entropy sources or define new ones via the kernel-level cryptographic framework.
A 3rd-party kernel module implementing /dev/random is also available for releases dating back to Solaris 2.4.
Read more about this topic: Entropy (computing)