[clug] October Canberra Linux Users Group meeting

[Rod Peters]

On Thursday 22 October 2009 05:00:03 linux-request at lists.samba.org wrote:
> Re: [clug] October Canberra Linux Users Group meeting
>  From: Michael James <michael at james.st>
>  To: Alex Satrapa <alexsatrapa at mac.com>, CLUG List <linux at lists.samba.org>
>
> On 21/10/2009, at 3:40 PM, Alex Satrapa wrote:
> > Please bring your laptops and experience/curiosity of virtualisation!
>
> The biggest problem I've had with virtualisation is timekeeping.
>
> On real hardware it's been a solved problem since the 90s.
> Run ntpd with a good many servers in a loose network.
> Kept the clocks accurate and was robust, using consensus
>   meant any server that went haywire was ignored.
>
> In virtual bottles having the clock counting ticks doesn't work,
>   as the machine isn't there all the time and misses ticks.
> Opensuse and SLES are bad at this, as they run the clock at 1000Hz.
>
> In a guest, ntpd's assumptions about drift don't hold.
> Running ntpd in multiple guests is an even bigger no-no
>   as they seem to fight over the clock.
> ?Does setting the hardware clock in a guest touch the hosts clock?
>
> Anyway I've tried to run ntpd once in the underlying host OS,
>   but I haven't found the way to feed that time up into the guests
>   as an absolute value, not ticks that can be mis-counted causing drift.
>
> My 2 seconds worth,
> michaelj

My VM are just "sandboxes" and I don;t bother with timekeeping.  Howver, for 
printing I just configure a network printer to the host-attached or other 
real network printer.

The hosts get their time from an IPCop ntp server.  Seems to me that the same 
would work for VM, but might require a port opened if NAT is used between 
host & VM.  Could then counter drift by more frequent synchronisations and 
the guests should not touch the host's clock.

openSUSE handles time synchronisation easily on a native installation - 
remains to be seen how NTP client on a guest fares.



Rod