Firstly: getentropy(2) is a /dev/random substitute, not urandom. You should call the process-context CSPRNG arc4random(3) in lieu of /dev/urandom. That should b

Firstly: getentropy(2) is a /dev/random substitute, not urandom. You should call the process-context CSPRNG arc4random(3) in lieu of /dev/urandom. That should be in the standard library (and hopefully will be added). (It uses ChaCha20 nowadays, not RC4.) Secondly: It can fail with EINVAL (bad pointer) or EIO (>256 bytes requested), but does not fail even in a condition where file descriptors are exhausted. I don't know of its behaviour if it is called too early in the boot process to have been safely seeded, but I hope it either errors loudly or blocks.