Re: /dev/random problem on 2.6.12-rc1

[Matt Mackall]

On Thu, Apr 07, 2005 at 05:36:59PM +0200, Simon Derr wrote:
> 
> 
> On Thu, 7 Apr 2005, Yura Pakhuchiy wrote:
> 
> > On Thu, 2005-04-07 at 14:40 +0200, Patrice Martinez wrote:
> > > When  using a machine with a  2612-rc 1kernel, I encounter problems
> > > reading /dev/random:
> > >  it simply nevers returns anything, and the process is blocked in the
> > > read...
> > > The easiest way to see it is to type:
> > >  od < /dev/random
> > >
> > > Any idea?
> >
> > Because, /dev/random use user input, mouse movements and other things to
> > generate next random number. Use /dev/urandom if you want version that
> > will never block your machine.
> >
> > Read "man 4 random" for details.
> >
> Something changed since previous versions of the kernel, I guess.
> Running `find /usr | wc' on a ssh session generates both network and disk
> activity, and you should not expect any other kind of input on a networked
> server.

FYI, network activity only generates entropy on a very small subset of
NICs, and probably not the one you're using. This is good, as network
activity is assumed passively observable/timable.

> Anyway, still zero bytes coming from /dev/random, for the few minutes I
> waited.

Are you and Patrice both experiencing this on the same machine? What
was the last kernel that was known to work for you? Do you see the
contents of /proc/sys/kernel/random/entropy_avail change over time?
Are there any other entropy consumers on your machine?

-- 
Mathematics is the supreme nostalgia of our time.
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