[Nix-dev] Why is rngd running by default?

Shea Levy shea at shealevy.com
Thu Nov 29 00:55:59 CET 2012


Hi Peter,

rngd has three potential sources of randomness: the RdRand instruction 
present in some x86 cpus, a system hardware random number generator at 
/dev/hwrng (not /dev/hwrandom), or a trusted platform module at 
/dev/tpm0. If your cpu doesn't support RdRand and you don't have either 
of those devices, rngd won't get triggered to start (and if it did, it 
would fail on startup).

~Shea

On 11/28/2012 06:48 PM, Peter Simons wrote:
> Hi guys,
>
> it appears that my NixOS host now features an rng daemon that's started
> by default. According to the man page, its purpose is to "feed random
> data from hardware device to kernel random device". The hardware device
> is supposed to be located at "/dev/hwrandom", but my machine doesn't
> have any such device. So I wonder why I'm running that daemon? Does it
> serve any purpose in the absence of special hardware?
>
> Take care,
> Peter
>
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