Switching to randomly generated hostnames

Kevin Gordon kgordon420 at gmail.com
Wed May 2 10:58:50 EDT 2012

On Wed, May 2, 2012 at 10:52 AM, Daniel Drake <dsd at laptop.org> wrote:

> On Tue, May 1, 2012 at 4:49 PM, John Gilmore <gnu at toad.com> wrote:
> >> Currently, XO hostnames are set on first boot in the following format:
> >> xo-A-B-C
> >> Where A, B and C are the last 3 bytes of the MAC address expressed in
> hex.
> >>
> >> In Nicaragua we are seeing cases where XOs have no hostname set, both
> >> on XO-1 and XO-1.5. On XO-1 this is presumably because libertas
> >> usb8388 init was never 100% reliable, and on XO-1.5 its presumably
> >> because the wireless card was DOA but was replaced after first boot.
> >
> > Why would we need to get it from the wireless card?  Isn't the
> > laptop's MAC address stored in the manufacturing data in motherboard
> > flash?
> Good point.

I believe I've seen cases where the mfg data doesnt match the actual real
MAC address.  If memory serves, it's on the older 1.5's, presumably where
the wireless module had been swapped out.  If that is the case, it might
not matter, since the use case is that the old module was probably trashed
and so the mfg data is still as unique as it needs to be.  Also, I'm at
work and don't have the old 1.5's in front of me  right now, so I could be
mistaken and the mfg data does get auto-magically updated when the module
is switched.  If so, sorry for the noise.

> >> I propose we move to generating hostnames in the same format as before
> >> (xo-A-B-C), but with A, B and C assigned as random hex digits on first
> >> boot.
> >> (If people are worried about collisions, maybe we add a D digit.)
> >
> > Existing hostnames have three bytes of info (e.g. xo-12-3a-49).
> > Particularly if you're going to generate them at random rather than
> > by prior assignment like MACs, why reduce the amount of unique
> > information (e.g. xo-1-a-4 or xo-1-a-4-d)?  Producing three random
> > bytes of info for the hostname, rather than 1.5 or 2 bytes, would
> > reduce the chance of collisions; and has the advantage of not
> > changing either the size or format of the hostnames, in case
> > anything else is depending on it.
> You're right. When I wrote "hex digits" I actually meant to write "hex
> bytes". i.e. I was not suggesting that we reduce the amount of data,
> only change where it comes from.
> Daniel
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