Date: Sun, 12 Jul 2015 18:14:59 -0700 From: Tim Kientzle <tim@kientzle.com> To: Yuri <yuri@rawbw.com> Cc: Freebsd hackers list <freebsd-hackers@freebsd.org> Subject: Re: Does /dev/random in virtual guests provide good random data? Message-ID: <CCCC361E-70E1-4BA4-9765-65653F40DBC7@kientzle.com> In-Reply-To: <55A2FB68.3070006@rawbw.com> References: <55A2FB68.3070006@rawbw.com>
next in thread | previous in thread | raw e-mail | index | archive | help
> 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.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CCCC361E-70E1-4BA4-9765-65653F40DBC7>