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On 4/25/2013 19:50, Alan McKinnon wrote: |
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> On 26/04/2013 01:42, William Kenworthy wrote: |
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>> Does anyone know a good guide to using time sync in VM's, for both |
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>> windows and linux (gentoo) guests using libvirt? Especially for guests |
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>> that are resumed, or the whole virtualisation system is hibernated? (ntp |
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>> refuses to resync after guest pause/save/restore/resume (known problem), |
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>> even with "tinker panic 0" |
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> |
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> |
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> That's not a bug, it's by design. |
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> |
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> If ntpd detects the clock is out by more than X seconds [1], it will not |
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> try to correct the difference, concluding that something is wrong and a |
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> human must decide. It can't easily tell the difference between a resumed |
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> guest (or even that it was resumed at all) and a severe problem. |
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> |
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> We fixed this by taking the easy route of least resistance; |
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> |
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> 1. run ntpdate on startup/restart once before ntpd starts |
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> 2. start ntpd as normal |
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> 3. a colleague wrote a $MAGIC_HOOK to detect resumed guests that runs |
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> ntpdate once |
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> |
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> True, it's a brutal solution and uses a baseball bat where some finesse |
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> might be less ugly, but it suits our needs just fine. |
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> |
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> [1] I forget what X is and am too lazy to look it up. Is it 30 seconds |
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> or thereabouts? |
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> |
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> |
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|
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"When first started, the daemon normally polls the servers listed in the |
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configuration file at 64-s intervals. In order to allow a sufficient |
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number of samples for the NTP algorithms to reliably discriminate |
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between correctly operating servers and possible intruders, at least |
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four valid messages from the majority of servers and peers listed in the |
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configuration file is required before the daemon can set the local |
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clock. However, if the difference between the client time and server |
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time is greater than the panic threshold, which defaults to 1000 s, the |
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daemon will send a message to the system log and shut down without |
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setting the clock." [0] |
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|
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[0] - http://doc.ntp.org/4.1.1/debug.htm |
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-- |
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staticsafe |
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Please don't top post - http://goo.gl/YrmAb |
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Don't CC me! I'm subscribed to whatever list I just posted on. |
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