[PATCH] mkswap: generate UUID

[Colin Watson]

On Fri, Jun 19, 2009 at 01:46:22AM -0500, Rob Landley wrote:
> On Thursday 18 June 2009 17:53:35 Colin Watson wrote:
> > On Thu, Jun 18, 2009 at 05:24:04PM -0500, Rob Landley wrote:
> > > The probability that a 128 bit random number will not be unique is 2^128.
> > >  I _guarantee_ you have no conception of how _big_ that is or you
> > > wouldn't be worrying about it.
> >
> > I used to work for a cryptography company; I actually do understand this
> > kind of scale just fine. I just don't trust rand(). :-)
> 
> Neither do I, that's why I used the system random number generator built into 
> the Linux kernel.

You did. Denys, whom I was replying to, didn't. I make no apology for
not having read your mail before you sent it.

> (Insert long discussion here about embedded systems with insufficient entropy 
> sources that don't preserve entropy across reboots, and how you can use 
> /dev/random instead so people get hangs and their system randomly fails in the 
> field instead.  By the way, did you _read_ old_e2fsprogs/gen_uuid.c?  Look at 
> the function on the bottom and trace your way back up, it uses 
> "uuid_generate_random" in _preference_ to the "assemble various system 
> information and hope it's unique" method.)

Yes, I did read it (before reading this message) and I have no quarrel
with its behaviour. Using /dev/urandom for preference makes perfect
sense here, as sane kernels already take care to stir whatever entropy
they can find in there.

I think you're arguing with things I never said ...

-- 
Colin Watson                                       [cjwatson at ubuntu.com]