The ChaCha20 DRNG implements the following seed sources which are activated during compile time. The noise sources are mutually exclusively activated by changing the Makefile - see the Makefile comments for the required changes.
The following seed sources are implemented:
Use of the getrandom(2) system call.
Use of the CPU Execution Time Jitter RNG as available at http://www.chronox.de/jent.html. The files jitterentropy-base.c, jitterentropy-base-user.h, and jitterentropy.h simply need to be copied into the root directory of the ChaCha20 DRNG code base. The Makefile will compile them together with the DRNG code to form a binary that is completely stand-alone without needing any external support functions.
Use of /dev/random.