Time skewing on Virtual Machine Debian

  • humbletech99
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Post 3+ Months Ago

I have a debian virtual machine in which the time keeps skewing. It has ntpd running against the same time server as all the other servers (which are all second accurate).

The Virtual Emulator is Microsoft's Virtual Server 2005 Enterprise Edition.

Is there a way I can stop this Debian system in the Virtual Machine from having this clock skew?

I have already tried something with the kernel parameter pit but this didn't seem to work.

Considering that the ntpd config is identical to all other servers and I know it works, I'm not sure why ntpd is so slow to correct this.

All other servers stay within 1 second accuracy, while this virtual one drifts out by 154 seconds (at the moment).

Perhaps I can make ntpd more shotgun or force the time to adjust according to what the time server says is the true time, or perhaps make it update more frequently?
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Post 3+ Months Ago

  • Daemonguy
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Post 3+ Months Ago

I have heard that MS's Virtual Servers create time discrepancies for the secondary operating systems (namely Linux). It's an issue with clock skew due to processor timing.

A lesser man might think there to be some conspiracy.

As for ntp... you can't run ntp in a virtual machine.
http://support.ntp.org/bin/view/Support/KnownOsIssues
  • humbletech99
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Post 3+ Months Ago

but ntp does work, kind of, it brings the time back to normal, but then it drifts off again... it's the time when it drifts off for some period before ntp brings it back inline that really bothers me.

I have the following in my logs
Code: [ Select ]
ntpd[2534]: synchronized to 192.168.1.151, stratum 3
ntpd[2534]: frequency error 512 PPM exceeds tolerance 500 PPM
  1. ntpd[2534]: synchronized to 192.168.1.151, stratum 3
  2. ntpd[2534]: frequency error 512 PPM exceeds tolerance 500 PPM
  • Daemonguy
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Post 3+ Months Ago

Sigh.

OK, you're right. I don't have any idea what I am talking about. Neither does ntp.org -- the folks responsible for ntp.

From the site:
Quote:
NTP was not designed to run inside of a virtual machine. It requires a high resolution system clock, with response times to clock interrupts that are serviced with a high level of accuracy. No known virtual machine is capable of meeting these requirements.


BTW, just because a program runs, does not mean it is 'working'.

Best of luck to you.
  • kc0tma
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Post 3+ Months Ago

Could you set up the host machine as a time server, then have the virtual machine query it's host for ntp? I don't see why that wouldn't work.
  • AnarchY SI
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Post 3+ Months Ago

Daemonguy wrote:
From the site:
Quote:
NTP was not designed to run inside of a virtual machine. It requires a high resolution system clock, with response times to clock interrupts that are serviced with a high level of accuracy. No known virtual machine is capable of meeting these requirements.

that could be why that might not work =\.. lol
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Post 3+ Months Ago

I can kind of understand that because I've overclocked systems and had their little time clock down in the corner go a bit fast over time, which is kind of the same idea as your quote...which I only read the first sentence of. It always pays to pay attention to details. That would be cool to set it up though, I've been wanting to get multiple virtual machines set up on one system and then create a domain and add them all to it, but I lack the processor and memory power to make it happen easily.
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Post 3+ Months Ago

hahah yea..reading everything is kind of important.
i made a post on the fedora forums, and then posted my solution and since that like 3 more people have posted with things to try. i'm like ...did you guys not read the part where i said i fixed it? lol
anywho yea..that would be a fun, interesting little project you've proposed ^_^
  • humbletech99
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Post 3+ Months Ago

hang on, rewind folks.

Did you see the bit where I said that ntp does in fact bring the time back in line to what it should be (in the 3rd post), and then it drifts off again for a while until ntp brings it back in line again...

So, ntp is not completely broken, but perhaps there is a way to increase the frequency with which is realigns to the ntp time server?

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