Hi folks, I''ve tried to mount a NTP service in DomU without success. Even when I''ve use the ntpdate <ntp_server> command directly, it doesn''t work. After several failed attempts I''ve discovered that domU is "automatically" syncronized with dom0. Because the checking has been easy: I''ve sync dom0 with X time and after all domU appears with X time too. Well... STFW.... http://lists.xensource.com/archives/html/xen-users/2005-05/msg00159.html http://lists.xensource.com/archives/html/xen-users/2005-11/msg00496.html ¿It is not possible to build a NTP service in domU which would be independent from dom0? According to my own tests, it seems not. If this issue is true I think it''s a big limitation for XEN. ¿what happens if you require to set up your domU with diferent NTP services (as clients)? I''m thinking in several clients I''ve around the world... -- Thanks, Jordi Espasa Clofent _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Jordi Espasa Clofent wrote:> ¿It is not possible to build a NTP service in domU which would be > independent from dom0? According to my own tests, it seems not.Set independent_wallclock.> If this issue is true I think it''s a big limitation for XEN. > ¿what happens if you require to set up your domU with diferent NTP > services (as clients)?Why though? There''s only one time to sync to to, and time sync within virtual machines is never going to be quite as accurate as bare hardware.. if you need millisecond accuracies then forget virtual machines (and use a realtime OS). I can''t think of a scenario where it would be a requirement to sync each domu off a different time source than the dom0 (even if you''re using them independently the closest and therefore most accurate time source to sync to is in fact the dom0). Xen does allow this, it''s just a bit pointless. Rarely the time on the domu seems to get screwed up (had one that was about 4 hours out), but I''ve only seen that happen a couple of times and a reboot of the domu fixed it. Tony _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Hi Jordi, well, you''re right. It''s not possible to have independent ntp clients running in your domU''s because you only have one physical harware clock, right? ;) And I can''t really understand your argumentation about having serveral domU''s "around the world"? In that case, don''t you have also several dom0''s arrounf the world at that places? cheers, marcel Jordi Espasa Clofent schrieb:> Hi folks, > > I''ve tried to mount a NTP service in DomU without success. Even when > I''ve use the ntpdate <ntp_server> command directly, it doesn''t work. > > After several failed attempts I''ve discovered that domU is > "automatically" syncronized with dom0. Because the checking has been > easy: I''ve sync dom0 with X time and after all domU appears with X time > too. > > Well... STFW.... > http://lists.xensource.com/archives/html/xen-users/2005-05/msg00159.html > http://lists.xensource.com/archives/html/xen-users/2005-11/msg00496.html > > ¿It is not possible to build a NTP service in domU which would be > independent from dom0? According to my own tests, it seems not. > > If this issue is true I think it''s a big limitation for XEN. > ¿what happens if you require to set up your domU with diferent NTP > services (as clients)? > > I''m thinking in several clients I''ve around the world... >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> well, you''re right. It''s not possible to have > independent ntp clients running in your domU''s because > you only have one physical harware clock, right? ;)It seems is possible with independent_wallclock parameter in /proc/sys/xen> And I can''t really understand your argumentation about having > serveral domU''s "around the world"? In that case, don''t you have > also several dom0''s arrounf the world at that places?Imagine that environment: several VPS for client who are in differents locations around the world. A real example is: my hosts are in Spain but I''ve several clients in south-america; some of them want to sync their VPS with their own time, not with spanish-time. -- Thanks, Jordi Espasa Clofent _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Wed, Jul 04, 2007 at 11:37:07AM +0200, Jordi Espasa Clofent wrote:> > well, you''re right. It''s not possible to have > > independent ntp clients running in your domU''s because > > you only have one physical harware clock, right? ;) > > It seems is possible with independent_wallclock parameter in /proc/sys/xen > > > And I can''t really understand your argumentation about having > > serveral domU''s "around the world"? In that case, don''t you have > > also several dom0''s arrounf the world at that places? > > Imagine that environment: several VPS for client who are in differents > locations around the world. > > A real example is: my hosts are in Spain but I''ve several clients in > south-america; some of them want to sync their VPS with their own time, not > with spanish-time.Unless they live in a different world with a different rotation period, that shouldn''t be a problem. In your specific case, the clients would only have to configer a correct timezone, with the hardware clock configured as in UTC. -- lfr 0/0 _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Jordi Espasa Clofent wrote:> A real example is: my hosts are in Spain but I''ve several clients in > south-america; some of them want to sync their VPS with their own time, > not with spanish-time. >Time sync simply doesn''t work like that. There is only one time - UTC. Everything else is an offset from that, which can be controlled per-user (or per-app if required) from the shell by altering environment variables. eg. $ TZ=Europe/London date Wed Jul 4 10:54:14 BST 2007 $ TZ=US/Pacific date Wed Jul 4 02:54:15 PDT 2007 Tony _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
---------- Forwarded message ---------- From: Galevsky <galevsky@gmail.com> Date: 4 juil. 2007 11:47 Subject: Re: [Xen-users] NTP service in DomU To: Jordi Espasa Clofent <sistemes.llistes@intergrid.cat> What's the matter ? Let's set up your time as UTC, dom0 will keep it updated, then set a different /etc/localtime file on each of your domU.... no issue here ;o) But you NEVER need more NTP services, because ntp keep your hardware clock up-to-date. How many hardware clock(s) do you have on a single machine ? :o) Only one of course. If many domU were able to modify the hardware clock with different setups (let's imagine a US localtime, a UTC, plus a Japan localtime domain) your motherboard would burn in a short time ;o) Let's dom0 deal with that. Then, you want to set different timezones on many domains, good. It is up to software. I advise you to read that kind of doc to manage time the way you want: http://tldp.org/HOWTO/TimePrecision-HOWTO/index.html Gal' 2007/7/4, Jordi Espasa Clofent <sistemes.llistes@intergrid.cat>:> Hi folks, > > I've tried to mount a NTP service in DomU without success. Even when > I've use the ntpdate <ntp_server> command directly, it doesn't work. > > After several failed attempts I've discovered that domU is > "automatically" syncronized with dom0. Because the checking has been > easy: I've sync dom0 with X time and after all domU appears with X time too. > > Well... STFW.... > http://lists.xensource.com/archives/html/xen-users/2005-05/msg00159.html > http://lists.xensource.com/archives/html/xen-users/2005-11/msg00496.html > > ¿It is not possible to build a NTP service in domU which would be > independent from dom0? According to my own tests, it seems not. > > If this issue is true I think it's a big limitation for XEN. > ¿what happens if you require to set up your domU with diferent NTP > services (as clients)? > > I'm thinking in several clients I've around the world... > > -- > Thanks, > Jordi Espasa Clofent > > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Jordi Espasa Clofent wrote:>> well, you''re right. It''s not possible to have >> independent ntp clients running in your domU''s because >> you only have one physical harware clock, right? ;) > > It seems is possible with independent_wallclock parameter in > /proc/sys/xen > >> And I can''t really understand your argumentation about having >> serveral domU''s "around the world"? In that case, don''t you have >> also several dom0''s arrounf the world at that places? > > Imagine that environment: several VPS for client who are in differents > locations around the world. > > A real example is: my hosts are in Spain but I''ve several clients in > south-america; some of them want to sync their VPS with their own > time, not with spanish-time.That''s not an NTP issue: that''s a timezone issue. You should *NOT, NOT, NOT* use NTP to try to manipulate your local times htis way: NTP is supposed to set the hardware clock, your timezone settings then adjust the display and handling of that for your local configuration. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Hi Jordi. You can try with echo 1 > /proc/sys/xen/independent_wallclock to obtain an independent clock for domU domain and synchronize with yours NTP servers.> Hi folks, > > I''ve tried to mount a NTP service in DomU without success. Even when > I''ve use the ntpdate <ntp_server> command directly, it doesn''t work. > > After several failed attempts I''ve discovered that domU is > "automatically" syncronized with dom0. Because the checking has been > easy: I''ve sync dom0 with X time and after all domU appears with X time too. > > Well... STFW.... > http://lists.xensource.com/archives/html/xen-users/2005-05/msg00159.html > http://lists.xensource.com/archives/html/xen-users/2005-11/msg00496.html > > ¿It is not possible to build a NTP service in domU which would be > independent from dom0? According to my own tests, it seems not. > > If this issue is true I think it''s a big limitation for XEN. > ¿what happens if you require to set up your domU with diferent NTP > services (as clients)? > > I''m thinking in several clients I''ve around the world... > > -- > Thanks, > Jordi Espasa Clofent > > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users > > -- > Aquest missatge ha estat verificat amb antivirus i > antispam. Es considera que esta net. > >-- Juan Antonio Vera Responsable Departament Informàtica Ajuntament Sant Adrià de Besòs Telf: 93 381 20 04 (ext 367) Fax: 93 381 70 56 Email: javera@sant-adria.net http://www.sant-adria.net -- Aquest missatge ha estat verificat amb antivirus i antispam. Es considera que esta net. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Galevsky wrote:> > But you NEVER need more NTP services, because ntp keep your hardware > clock up-to-date. How many hardware clock(s) do you have on a single > machine ? :o) > Only one of course.I think he''s gotten the hint now..... _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Hi Tony, On Wed, Jul 04, 2007 at 10:30:09AM +0100, Tony Hoyle wrote:> Rarely the time on the domu seems to get screwed up (had one that was > about 4 hours out), but I''ve only seen that happen a couple of times and > a reboot of the domu fixed it.If I do not use NTP in every domu then every domu drifts by minutes per day. This is my experience with every version of xen 2.x through 3.0.3 on many different types of hardware. I''m glad if you don''t experience this but I think I''m not alone in seeing it.. :( Cheers, Andy _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users