[Sugar-devel] Clocks on XOs

Bernie Innocenti bernie at codewiz.org
Sat Jul 3 09:54:16 EDT 2010

El Fri, 02-07-2010 a las 20:15 -0700, Hal Murray escribió:

> Is that one of the old XOs that had troubles with the tiny battery feeding 
> the TOY/RTC clock when the main battery and wall power are both disconnected? 
>  I forget the details, but I think there was a problem with the battery 
> holder.

Likely so, but the software should be able to compensate for it. After
discussing it on IRC, it seems that olpc-update-query should
automatically update the clock from the OATS server.

> NetworkManager used to call ntpdate when it setup a connection.  Was that an 
> OLPC addition?

We figured out that the ntp package has never been present on the XO

> I think this area gets tangled up with security and lease checking.  Do we 
> want/need two separate modes, one for the secure case and another for 
> developers without a school server?


We discussed the security implications of using unauthenticated ntp on
XOs with anti-theft enabled yesterday on IRC. The concern is that a
clever thief could setup a LAN with DHCP, DNS and NTP to set a date in
te past and thus subvert the leases expiration scheme.

However, with root access on the laptop, one does not need to bother so
much: they could simply change the time from the console or, better,
in /etc/rc.local.

There's no way to practical way to implement effective anti-theft
without taking away root from the user. And once we take away root
access, we've also taken away olpc's principle #1: child ownership.

> What are the school servers doing to keep their clocks reasonable?

They're using ntp, with the Fedora pool of ntp servers.

> > Why aren't we using ntp? 
> ntp is probably overkill for XOs.  Besides, who would want to give up that 
> much ram?  On top of that, ntpd doesn't get along with power saving mode.

Wow, 2MB of RSS! I had no idea ntp was such a hog.

> Aside from quirks like this one, is time on the XO normally good enough?

I would have to check...

   // Bernie Innocenti - http://codewiz.org/
 \X/  Sugar Labs       - http://sugarlabs.org/

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