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Subject: Re: Does /dev/random in virtual guests provide good random data?
From: Tim Kientzle <tim@kientzle.com>
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Date: Sun, 12 Jul 2015 18:14:59 -0700
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To: Yuri <yuri@rawbw.com>
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> On Jul 12, 2015, at 4:42 PM, Yuri <yuri@rawbw.com> wrote:
>=20
> 'cat /dev/random' in Linux VM (tried Ubuntu and Arch) is extremely =
slow, supposedly because VM runs out of entropy. This cat sometimes =
stops for minutes, and usually produces very few bytes per minute. =
Randomly clicking on the window helps speed it up a bit.
>=20
> Same in FreeBSD VM produces steady ~28MB/s stream.
>=20
> Does FreeBSD VM do something special for entropy, or the resulting =
stream actually lacks entropy, or maybe Linux does something wrong?

Here=E2=80=99s a good discussion of the difference between /dev/random =
and /dev/urandom on Linux:

   http://www.2uo.de/myths-about-urandom/

In particular, it has this interesting comment:

     FreeBSD does the right thing: they don't have the distinction
     between /dev/random and /dev/urandom, both are the same
     device. At startup /dev/random blocks once until enough starting
     entropy has been gathered. Then it won't block ever again.