Red Hat LINUX VIRTUAL SERVER 4.7 - ADMINISTRATION Specifications download pdf (Page 15)

Installing and Configuring Linux Guest Operating Systems

Theconfigurationdirectivetinker panic 0instructsNTPnottogiveupifitseesalargejumpintime.This

isimportantforcopingwithlargetimedriftsandalsoresumingvirtualmachinesfromtheirsuspendedstate.

Itisalsoimportantnottousethelocalclock,oftenreferredtoastheundisciplinedlocalclock,asatimesource.

NTPhasatendencytofallbacktothissourceinpreferencetotheremoteserverswhenthereisalargeamount

oftimedrift.

Anexampleofsuchaconfigurationis:

server 127.127.1.0

fudge 127.127.1.0 stratum 10

Commentoutbothoftheselinesfrom/etc/ntp.conf.

AftermakingchangestotheNTPconfiguration,youmustrestarttheNTPdaemon.Seeyouroperatingsystem

vendor’sdocumentationfordetails.

VMware Tools Time Synchronization Configuration

WhenusingNTPintheguestoperatingsystem,disableVMwareToolsperiodictimesynchronizationusing

oneofthefollowingoptions:

1Settools.syncTime = "0"intheconfigurationfile(.vmxfile)ofthevirtualmachine.

2 DeselectTimesynchronizationbetweenthevirtualmachineandthehostoperatingsysteminthe

VMwareToolstoolboxGUIin

theguestoperatingsystem.

3Runthecommandvmware-guestd --cmd "vmx.set_option synctime 1 0"intheguestoperating

system.

Theseoptionsdonotdisableone‐timesynchronizationsdonebyVMwareToolsforeventssuchastools

startup,takingasnapshot,revertingtoasnapshot,resumingfromsuspend,orVMotion.Theseevents

synchronizetimeintheguestoperatingsystem

withtimeinthehostoperatingsystem,soitisimportantto

makesurethatthehostoperatingsystem’stimeiscorrect.

TodothisforVMwareACE,VMwareFusion,VMwarePlayer,VMwareServer,andVMwareWorkstation,run

timesynchronizationsoftwaresuchasNTPorw32timeonthehost.ForVMware

ESX,runNTPintheservice

console.ForVMwareESXi,runNTPintheVMkernel.

Virtual Hardware Clock Configuration

WhenconfiguringaLinuxguestoperatingsystem,ifyouaregivenachoicebetweenkeepingthe“hardware”

clock(thatis,thevirtualCMOStimeofdayclock)inUTCorlocaltime,chooseUTC.Thisavoidsanyconfusion

whenyourlocaltimechangesbetweenstandardanddaylightsavingtime(inEngland,

summertime).

Additional Notes

ThissectionprovidesadditionalusefulnotesforLinuxadministratorswhowanttooptimizetheirLinuxguest

operatingsystems.Thesenotesdonotdetailstep‐by‐stepinstructionsforfine‐tuningyourLinuxvirtual

machines,buttheyofferfurtherinsightintounderstandingthebehaviorofyourvirtualmachines.Thissection

coversthe

followingtopics:

 “AsynchronousI/O”onpage 16

 “LinuxTimerRatesforVirtualMachinesonVMwareESX”onpage 16

 “LinuxSwappiness”onpage 17

 “ParavirtualizationandVirtualMachineInterface”onpage 17

 “OpenVirtualMachineTools”onpage 19

OTEThedirectivetinker panic 0mustbeatthetopofthentp.conffile.

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