Mailing List Archive

On Thu, May 12, 2005 at 10:42:53AM -0700, andrew mathes wrote:
> So, from what it looks like (on my servers and the docs), all my domains
> get their time from DomO. Which I have setting itself through NTP, and
> the dom0 looks good. However, All of the domains are 1.5 seconds off, and
> won't ntp themselves on, also, an identical server, all the domains are
> .768 seconds off (off of the server i'm ntping to) , but both domO's are
> withing (.02) and seem to narrow in as NTP is supposed to.
>
> So, question is, 1) what is going on here, and 2) can anything be done
> about it?
Are you using OpenNTPD by any chance?
My machines suffered from inaccurate clocks in DomU's, even though the
clock was very accurate in Dom0. Switching to regular ntpd solved this,
DomU immediately used the correct time shortly after starting ntpd.
--
Alex Tomkins <tomkins@darkzone.net>

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don't the DomU's just get their time from DomO? Ie. ... even if they
weren't running ntp they'd always be synced with whatever DomO thought
about system time?

Maybe i'm way off

On Thu, 12 May 2005, Alex Tomkins wrote:

> On Thu, May 12, 2005 at 10:42:53AM -0700, andrew mathes wrote:
>> So, from what it looks like (on my servers and the docs), all my domains
>> get their time from DomO. Which I have setting itself through NTP, and
>> the dom0 looks good. However, All of the domains are 1.5 seconds off, and
>> won't ntp themselves on, also, an identical server, all the domains are
>> .768 seconds off (off of the server i'm ntping to) , but both domO's are
>> withing (.02) and seem to narrow in as NTP is supposed to.
>>
>> So, question is, 1) what is going on here, and 2) can anything be done
>> about it?
> Are you using OpenNTPD by any chance?
> My machines suffered from inaccurate clocks in DomU's, even though the
> clock was very accurate in Dom0. Switching to regular ntpd solved this,
> DomU immediately used the correct time shortly after starting ntpd.
> --
> Alex Tomkins <tomkins@darkzone.net>
>

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On 5/12/05, andrew mathes <amathes@backnine.org> wrote:
> don't the DomU's just get their time from DomO? Ie. ... even if they
> weren't running ntp they'd always be synced with whatever DomO thought
> about system time?
>
> Maybe i'm way off
>
> On Thu, 12 May 2005, Alex Tomkins wrote:
>
> > On Thu, May 12, 2005 at 10:42:53AM -0700, andrew mathes wrote:
> >> So, from what it looks like (on my servers and the docs), all my domains
> >> get their time from DomO. Which I have setting itself through NTP, and
> >> the dom0 looks good. However, All of the domains are 1.5 seconds off, and
> >> won't ntp themselves on, also, an identical server, all the domains are
> >> .768 seconds off (off of the server i'm ntping to) , but both domO's are
> >> withing (.02) and seem to narrow in as NTP is supposed to.
> >>
> >> So, question is, 1) what is going on here, and 2) can anything be done
> >> about it?
> > Are you using OpenNTPD by any chance?
> > My machines suffered from inaccurate clocks in DomU's, even though the
> > clock was very accurate in Dom0. Switching to regular ntpd solved this,
> > DomU immediately used the correct time shortly after starting ntpd.
> > --
> > Alex Tomkins <tomkins@darkzone.net>

Andrew,

Please remember, you allways shoult treat each virtual machine
like a completely separated host! So far, you shoul configure ntpd
to get time from -possibly- the same host as you dom0 is getting
time. Try that. It won't hurt :) And I bet you will feel happy with
the result :)

--
Bye,
Fernando Maior
LPIC/1 31908

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yeah, i'm already doing that, I was just saying, it *seemed* like they
were getting their time from domain0, and weren't actually changing their
own clocks in accordance with syncing with the same ntpd server.

especially since they're all off by exactly the same amount ... and
running ntpdate doesn't seem to have any effect whatsoever?

On Thu, 12 May 2005, Fernando Maior wrote:

> On 5/12/05, andrew mathes <amathes@backnine.org> wrote:
>> don't the DomU's just get their time from DomO? Ie. ... even if they
>> weren't running ntp they'd always be synced with whatever DomO thought
>> about system time?
>>
>> Maybe i'm way off
>>
>> On Thu, 12 May 2005, Alex Tomkins wrote:
>>
>>> On Thu, May 12, 2005 at 10:42:53AM -0700, andrew mathes wrote:
>>>> So, from what it looks like (on my servers and the docs), all my domains
>>>> get their time from DomO. Which I have setting itself through NTP, and
>>>> the dom0 looks good. However, All of the domains are 1.5 seconds off, and
>>>> won't ntp themselves on, also, an identical server, all the domains are
>>>> .768 seconds off (off of the server i'm ntping to) , but both domO's are
>>>> withing (.02) and seem to narrow in as NTP is supposed to.
>>>>
>>>> So, question is, 1) what is going on here, and 2) can anything be done
>>>> about it?
>>> Are you using OpenNTPD by any chance?
>>> My machines suffered from inaccurate clocks in DomU's, even though the
>>> clock was very accurate in Dom0. Switching to regular ntpd solved this,
>>> DomU immediately used the correct time shortly after starting ntpd.
>>> --
>>> Alex Tomkins <tomkins@darkzone.net>
>
> Andrew,
>
> Please remember, you allways shoult treat each virtual machine
> like a completely separated host! So far, you shoul configure ntpd
> to get time from -possibly- the same host as you dom0 is getting
> time. Try that. It won't hurt :) And I bet you will feel happy with
> the result :)
>
> --
> Bye,
> Fernando Maior
> LPIC/1 31908
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users
>

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> yeah, i'm already doing that, I was just saying, it *seemed*
> like they were getting their time from domain0, and weren't
> actually changing their own clocks in accordance with syncing
> with the same ntpd server.

> especially since they're all off by exactly the same amount
> ... and running ntpdate doesn't seem to have any effect whatsoever?

If you don't run ntp in the domU's, it should just work.

If you want to run ntp in the domU, try:
echo 1 > /proc/sys/xen/independent_wallclock

I guess we could be smarter about this, and make the wall clock
independent automatically if someone does an adjtimex syscall. Anyone
got any comments on this?

Ian


> On Thu, 12 May 2005, Fernando Maior wrote:
>
> > On 5/12/05, andrew mathes <amathes@backnine.org> wrote:
> >> don't the DomU's just get their time from DomO? Ie. ...
> even if they
> >> weren't running ntp they'd always be synced with whatever DomO
> >> thought about system time?
> >>
> >> Maybe i'm way off
> >>
> >> On Thu, 12 May 2005, Alex Tomkins wrote:
> >>
> >>> On Thu, May 12, 2005 at 10:42:53AM -0700, andrew mathes wrote:
> >>>> So, from what it looks like (on my servers and the docs), all my
> >>>> domains get their time from DomO. Which I have setting itself
> >>>> through NTP, and the dom0 looks good. However, All of
> the domains
> >>>> are 1.5 seconds off, and won't ntp themselves on, also, an
> >>>> identical server, all the domains are
> >>>> .768 seconds off (off of the server i'm ntping to) , but both
> >>>> domO's are withing (.02) and seem to narrow in as NTP is
> supposed to.
> >>>>
> >>>> So, question is, 1) what is going on here, and 2) can
> anything be
> >>>> done about it?
> >>> Are you using OpenNTPD by any chance?
> >>> My machines suffered from inaccurate clocks in DomU's,
> even though
> >>> the clock was very accurate in Dom0. Switching to regular ntpd
> >>> solved this, DomU immediately used the correct time
> shortly after starting ntpd.
> >>> --
> >>> Alex Tomkins <tomkins@darkzone.net>
> >
> > Andrew,
> >
> > Please remember, you allways shoult treat each virtual
> machine like a
> > completely separated host! So far, you shoul configure ntpd to get
> > time from -possibly- the same host as you dom0 is getting time. Try
> > that. It won't hurt :) And I bet you will feel happy with
> the result
> > :)
> >
> > --
> > Bye,
> > Fernando Maior
> > LPIC/1 31908
> >
> > _______________________________________________
> > 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
>

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Ian Pratt wrote:

>
>
>
>
>>yeah, i'm already doing that, I was just saying, it *seemed*
>>like they were getting their time from domain0, and weren't
>>actually changing their own clocks in accordance with syncing
>>with the same ntpd server.
>>
>>
>
>
>
>>especially since they're all off by exactly the same amount
>>... and running ntpdate doesn't seem to have any effect whatsoever?
>>
>>
>
>If you don't run ntp in the domU's, it should just work.
>
>If you want to run ntp in the domU, try:
> echo 1 > /proc/sys/xen/independent_wallclock
>
>I guess we could be smarter about this, and make the wall clock
>independent automatically if someone does an adjtimex syscall. Anyone
>got any comments on this?
>
>Ian
>
>
>
>
>>On Thu, 12 May 2005, Fernando Maior wrote:
>>
>>
>>
>>>On 5/12/05, andrew mathes <amathes@backnine.org> wrote:
>>>
>>>
>>>>don't the DomU's just get their time from DomO? Ie. ...
>>>>
>>>>
>>even if they
>>
>>
>>>>weren't running ntp they'd always be synced with whatever DomO
>>>>thought about system time?
>>>>
>>>>Maybe i'm way off
>>>>
>>>>On Thu, 12 May 2005, Alex Tomkins wrote:
>>>>
>>>>
>>>>
>>>>>On Thu, May 12, 2005 at 10:42:53AM -0700, andrew mathes wrote:
>>>>>
>>>>>
>>>>>>So, from what it looks like (on my servers and the docs), all my
>>>>>>domains get their time from DomO. Which I have setting itself
>>>>>>through NTP, and the dom0 looks good. However, All of
>>>>>>
>>>>>>
>>the domains
>>
>>
>>>>>>are 1.5 seconds off, and won't ntp themselves on, also, an
>>>>>>identical server, all the domains are
>>>>>>.768 seconds off (off of the server i'm ntping to) , but both
>>>>>>domO's are withing (.02) and seem to narrow in as NTP is
>>>>>>
>>>>>>
>>supposed to.
>>
>>
>>>>>>So, question is, 1) what is going on here, and 2) can
>>>>>>
>>>>>>
>>anything be
>>
>>
>>>>>>done about it?
>>>>>>
>>>>>>
>>>>>Are you using OpenNTPD by any chance?
>>>>>My machines suffered from inaccurate clocks in DomU's,
>>>>>
>>>>>
>>even though
>>
>>
>>>>>the clock was very accurate in Dom0. Switching to regular ntpd
>>>>>solved this, DomU immediately used the correct time
>>>>>
>>>>>
>>shortly after starting ntpd.
>>
>>
>>>>>--
>>>>>Alex Tomkins <tomkins@darkzone.net>
>>>>>
>>>>>
>>>Andrew,
>>>
>>>Please remember, you allways shoult treat each virtual
>>>
>>>
>>machine like a
>>
>>
>>>completely separated host! So far, you shoul configure ntpd to get
>>>time from -possibly- the same host as you dom0 is getting time. Try
>>>that. It won't hurt :) And I bet you will feel happy with
>>>
>>>
>>the result
>>
>>
>>>:)
>>>
>>>--
>>>Bye,
>>>Fernando Maior
>>>LPIC/1 31908
>>>
>>>_______________________________________________
>>>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
>>
>>
>>
>
>_______________________________________________
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>http://lists.xensource.com/xen-users
>
>
>
Something to think about, if the vms are syncing off the Dom0 then
there would be no way to configure the guest systems in different time
zones. To me that would be a plus with the vm's.



--
Paul Edgar
Content Delivery System
IBM/Austin
javaoops@us.ibm.com

No trees were destroyed in the sending of this message, however, a significant number of electrons were terribly inconvenienced.

Ian Pratt wrote:

>
>
>
>
>>yeah, i'm already doing that, I was just saying, it *seemed*
>>like they were getting their time from domain0, and weren't
>>actually changing their own clocks in accordance with syncing
>>with the same ntpd server.
>>
>>
>
>
>
>>especially since they're all off by exactly the same amount
>>... and running ntpdate doesn't seem to have any effect whatsoever?
>>
>>
>
>If you don't run ntp in the domU's, it should just work.
>
>If you want to run ntp in the domU, try:
> echo 1 > /proc/sys/xen/independent_wallclock
>
>I guess we could be smarter about this, and make the wall clock
>independent automatically if someone does an adjtimex syscall. Anyone
>got any comments on this?
>
>Ian
>
>
>
Don't auto-detect based on adjtimex. It would be too easy and too
confusing to accidentally make such a call once, and then not realize
that you would no longer be auto-synchronized.

Instead, make independent_wallclock be a config file option that is
overridable by proc.

-Tupshin

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yes, changing this value allowed domU independent syncing, thank you very
much!!

i agree on the config file option if possible ...

On Thu, 12 May 2005, Tupshin Harper wrote:

> Ian Pratt wrote:
>
>>
>>
>>
>>
>>> yeah, i'm already doing that, I was just saying, it *seemed*
>>> like they were getting their time from domain0, and weren't
>>> actually changing their own clocks in accordance with syncing
>>> with the same ntpd server.
>>>
>>>
>>
>>
>>
>>> especially since they're all off by exactly the same amount
>>> ... and running ntpdate doesn't seem to have any effect whatsoever?
>>>
>>>
>>
>> If you don't run ntp in the domU's, it should just work.
>>
>> If you want to run ntp in the domU, try:
>> echo 1 > /proc/sys/xen/independent_wallclock
>>
>> I guess we could be smarter about this, and make the wall clock
>> independent automatically if someone does an adjtimex syscall. Anyone
>> got any comments on this?
>>
>> Ian
>>
>>
>>
> Don't auto-detect based on adjtimex. It would be too easy and too
> confusing to accidentally make such a call once, and then not realize
> that you would no longer be auto-synchronized.
>
> Instead, make independent_wallclock be a config file option that is
> overridable by proc.
>
> -Tupshin
>

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I think it's perfect the way it is.

Run NTP in dom0, all the domU's then have synchronized time.

I can still set timezones on all of these boxes independantly.
Timezone has nothing to do with NTP synchronization.

Tim:>


> yeah, i'm already doing that, I was just saying, it *seemed*
> like they were getting their time from domain0, and weren't
> actually changing their own clocks in accordance with syncing
> with the same ntpd server.

> especially since they're all off by exactly the same amount
> ... and running ntpdate doesn't seem to have any effect whatsoever?

If you don't run ntp in the domU's, it should just work.

If you want to run ntp in the domU, try:
echo 1 > /proc/sys/xen/independent_wallclock

I guess we could be smarter about this, and make the wall clock
independent automatically if someone does an adjtimex syscall. Anyone
got any comments on this?

Ian

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Xen-users@lists.xensource.com
http://lists.xensource.com/xen-users

any idea why all my DomU's were exactly the same offset wrong from my DomO
then?

I agree, it is great if it works ... but if it's off for some reason, i'd
like to be able to fix it. (otherwise i may as well use windows ...)

On Fri, 13 May 2005, Tim Durack wrote:

> I think it's perfect the way it is.
>
> Run NTP in dom0, all the domU's then have synchronized time.
>
> I can still set timezones on all of these boxes independantly.
> Timezone has nothing to do with NTP synchronization.
>
> Tim:>
>
>
>> yeah, i'm already doing that, I was just saying, it *seemed*
>> like they were getting their time from domain0, and weren't
>> actually changing their own clocks in accordance with syncing
>> with the same ntpd server.
>
>> especially since they're all off by exactly the same amount
>> ... and running ntpdate doesn't seem to have any effect whatsoever?
>
> If you don't run ntp in the domU's, it should just work.
>
> If you want to run ntp in the domU, try:
> echo 1 > /proc/sys/xen/independent_wallclock
>
> I guess we could be smarter about this, and make the wall clock
> independent automatically if someone does an adjtimex syscall. Anyone
> got any comments on this?
>
> Ian
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users
>

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> any idea why all my DomU's were exactly the same offset wrong
> from my DomO then?

You've got two people (dom0 and domU) trying to adjust time at the same
time, which is bound to lead to confusion.

Ian

> I agree, it is great if it works ... but if it's off for some
> reason, i'd like to be able to fix it. (otherwise i may as
> well use windows ...)
>
> On Fri, 13 May 2005, Tim Durack wrote:
>
> > I think it's perfect the way it is.
> >
> > Run NTP in dom0, all the domU's then have synchronized time.
> >
> > I can still set timezones on all of these boxes independantly.
> > Timezone has nothing to do with NTP synchronization.
> >
> > Tim:>
> >
> >
> >> yeah, i'm already doing that, I was just saying, it *seemed* like
> >> they were getting their time from domain0, and weren't actually
> >> changing their own clocks in accordance with syncing with the same
> >> ntpd server.
> >
> >> especially since they're all off by exactly the same
> amount ... and
> >> running ntpdate doesn't seem to have any effect whatsoever?
> >
> > If you don't run ntp in the domU's, it should just work.
> >
> > If you want to run ntp in the domU, try:
> > echo 1 > /proc/sys/xen/independent_wallclock
> >
> > I guess we could be smarter about this, and make the wall clock
> > independent automatically if someone does an adjtimex
> syscall. Anyone
> > got any comments on this?
> >
> > Ian
> >
> > _______________________________________________
> > Xen-users mailing list
> > Xen-users@lists.xensource.com
> > http://lists.xensource.com/xen-users
> >
>
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anyone know where I should set this so that it stays "1" after reboot?
I'm not sure the best way to do this ...

thanks a bunch

On Thu, 12 May 2005, andrew mathes wrote:

> yes, changing this value allowed domU independent syncing, thank you very
> much!!
>
> i agree on the config file option if possible ...
>
> On Thu, 12 May 2005, Tupshin Harper wrote:
>
>> Ian Pratt wrote:
>>
>> >
>> >
>> >
>> >
>> > > yeah, i'm already doing that, I was just saying, it *seemed*
>> > > like they were getting their time from domain0, and weren't
>> > > actually changing their own clocks in accordance with syncing
>> > > with the same ntpd server.
>> > >
>> > >
>> >
>> >
>> >
>> > > especially since they're all off by exactly the same amount
>> > > ... and running ntpdate doesn't seem to have any effect whatsoever?
>> > >
>> > >
>> >
>> > If you don't run ntp in the domU's, it should just work.
>> >
>> > If you want to run ntp in the domU, try:
>> > echo 1 > /proc/sys/xen/independent_wallclock
>> >
>> > I guess we could be smarter about this, and make the wall clock
>> > independent automatically if someone does an adjtimex syscall. Anyone
>> > got any comments on this?
>> >
>> > Ian
>> >
>> >
>> >
>> Don't auto-detect based on adjtimex. It would be too easy and too
>> confusing to accidentally make such a call once, and then not realize
>> that you would no longer be auto-synchronized.
>>
>> Instead, make independent_wallclock be a config file option that is
>> overridable by proc.
>>
>> -Tupshin
>>
>
> _______________________________________________
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>
>

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andrew mathes wrote:
> anyone know where I should set this so that it stays "1" after reboot?
> I'm not sure the best way to do this ...

Just add it to your rc.local or equivalent startup script. (It'll be
distribution specific.)

--
Andrew Thompson
http://aktzero.com/

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