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October Canberra Linux Users Group meeting
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October Canberra Linux Users Group meeting
by Chris Smart-7
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Canberra Linux Users Group Meeting - 22nd October 2009
====================================================== Date: 22nd October 2009 (Fourth Thursday of the month) Time: 19:00 - 21:00 (or when it finishes) Speaker: Alex Satrapa Abstract: Alex will be talking about either database development or replication. If you see this message he hasn't decided which. Venue: Room N101 Computer Science and Information Technology Building North Road The Australian National University See http://clug.org.au/ for more directions and a map Food/drink: Pizza and soft drink/juice. Come hungry, and bring about $6 to cover the cost of your share if you want some. If you would like to give a talk at a future meeting, please email me. -- linux mailing list linux@... https://lists.samba.org/mailman/listinfo/linux |
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Re: October Canberra Linux Users Group meeting
by Alex Satrapa-5
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On 20/10/2009, at 09:00 , chris@... wrote:
> Abstract: Alex will be talking about either database development > or replication. If you see this message he hasn't > decided which. I'm intending to provide a newbie intro to - virtualisation software I've played with - cross-platform VM images - bridged, NAT, host-only networks and why you'd use one or the other - preparing new guests - PXE boot & over-the-network installation of Debian and Ubuntu - Using Chef to manage guest systems (this based on feedback from the list over the past month or so) Then I hope to open the floor to see how much you guys can teach me (and thus each other, and by extension the RotW) about setting up consumer-level VM farms for things such as playing with Asterisk, providing a testing environment for that change you want to make to your client's web site, providing an isolated environment for security penetration games, determining just how much faster Karmic Koala is at booting than Hardy Heron, etc. In particular, I'm hoping people can contribute: - experience with Parallels & VirtualBox - experience with Zen para-virtualisation - experience with bare-boot + puppet/chef vs FAI - other issues I've raised on the list The main thing I'm hoping to achieve is to help some folks who haven't touched virtualisation yet get some idea of just how useful it is. More importantly, I'd like to provide a framework and "tips for new players" for playing with virtualisation. Please bring your laptops and experience/curiosity of virtualisation! Alex -- linux mailing list linux@... https://lists.samba.org/mailman/listinfo/linux |
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Re: October Canberra Linux Users Group meeting
by Michael James-6
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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 -- Well theme my emoticons disgusted. What has Linux come to? Michael James -- linux mailing list linux@... https://lists.samba.org/mailman/listinfo/linux |
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Re: October Canberra Linux Users Group meeting
by Robert Edwards-3
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Michael James wrote:
> > 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 > > I've been playing with OpenVZ a bit recently (www.openvz.org) - which is OS level virtualization. It's really the Linux version of Solaris's containers and possibly a little more featureful than BSDs jails. In OpenVZ there is only one kernel and if it can keep time (with the aid of, eg., ntp) then all the "guest"s (actually "Virtual Environments" - VEs) get the correct time for free. Interesting thing is that the OpenVZ documentation recommends against running any services other than SSH in the "Hardware/Host Node" (HN) and instead running ntpd in one of the VEs. This VE then needs special permission to be able to set the system time on behalf of the HN and the other VEs. Seems to work well enough. Cheers, Bob Edwards. -- linux mailing list linux@... https://lists.samba.org/mailman/listinfo/linux |
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Re: October Canberra Linux Users Group meeting
by Alex Satrapa-5
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On 22/10/2009, at 15:19 , Rod Peters wrote:
> 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. The problem with VMs is not so much the drift while they're running, so much as what happens when you "suspend" a virtual machine (as opposed to telling the guest OS to suspend-to-disk or go to sleep), then "resume" that machine some days later. In this case, the guest OS has not received any indication that the hardware is going to sleep, nor has it received any indication that the hardware has been woken up. One moment it's 11:00 on October 15 2008, the next it's being told by NTP that the date is actually 14:56 on July 26 2009. There's not much a system can to do cope with this kind of behaviour, and it's one reason I'm leaning towards the "crash cleanly and reboot from scratch" approach. Alex -- linux mailing list linux@... https://lists.samba.org/mailman/listinfo/linux |
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