| 1 | <?xml version='1.0' encoding='UTF-8'?>
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| 2 | <!DOCTYPE topic PUBLIC "-//OASIS//DTD DITA Topic//EN" "topic.dtd">
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| 3 | <topic xml:lang="en-us" id="changetimesync">
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| 4 | <title>Tuning the Guest Additions Time Synchronization Parameters</title>
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| 5 |
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| 6 | <body>
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| 7 | <p>
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| 8 | The <ph conkeyref="vbox-conkeyref-phrases/product-name"/> Guest Additions ensure that the guest's
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| 9 | system time is synchronized with the host time. There are
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| 10 | several parameters which can be tuned. The parameters can be set
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| 11 | for a specific VM using the following command:
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| 12 | </p>
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| 13 | <pre xml:space="preserve">$ VBoxManage guestproperty set <varname>VM-name</varname> "/VirtualBox/GuestAdd/VBoxService/<varname>property</varname>" <varname>value</varname>
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| 14 | </pre>
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| 15 | <p><varname>property</varname> is one of the following:
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| 16 | </p>
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| 17 | <dl>
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| 18 | <dlentry>
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| 19 | <dt><codeph>--timesync-interval</codeph>
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| 20 | </dt>
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| 21 | <dd>
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| 22 | <p>
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| 23 | Specifies the interval at which to synchronize the time
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| 24 | with the host. The default is 10000 ms (10 seconds).
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| 25 | </p>
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| 26 | </dd>
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| 27 | </dlentry>
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| 28 | <dlentry>
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| 29 | <dt><codeph>--timesync-min-adjust</codeph>
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| 30 | </dt>
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| 31 | <dd>
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| 32 | <p>
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| 33 | The minimum absolute drift value measured in milliseconds
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| 34 | to make adjustments for. The default is 1000 ms on OS/2
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| 35 | and 100 ms elsewhere.
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| 36 | </p>
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| 37 | </dd>
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| 38 | </dlentry>
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| 39 | <dlentry>
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| 40 | <dt><codeph>--timesync-latency-factor</codeph>
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| 41 | </dt>
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| 42 | <dd>
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| 43 | <p>
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| 44 | The factor to multiply the time query latency with to
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| 45 | calculate the dynamic minimum adjust time. The default is
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| 46 | 8 times, which means as follows:
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| 47 | </p>
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| 48 | <p>
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| 49 | Measure the time it takes to determine the host time, the
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| 50 | guest has to contact the VM host service which may take
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| 51 | some time. Multiply this value by 8 and do an adjustment
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| 52 | only if the time difference between host and guest is
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| 53 | bigger than this value. Do not do any time adjustment
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| 54 | otherwise.
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| 55 | </p>
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| 56 | </dd>
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| 57 | </dlentry>
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| 58 | <dlentry>
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| 59 | <dt><codeph>--timesync-max-latency</codeph>
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| 60 | </dt>
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| 61 | <dd>
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| 62 | <p>
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| 63 | The max host timer query latency to accept. The default is
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| 64 | 250 ms.
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| 65 | </p>
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| 66 | </dd>
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| 67 | </dlentry>
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| 68 | <dlentry>
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| 69 | <dt><codeph>--timesync-set-threshold</codeph>
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| 70 | </dt>
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| 71 | <dd>
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| 72 | <p>
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| 73 | The absolute drift threshold, given as milliseconds where
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| 74 | to start setting the time instead of trying to smoothly
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| 75 | adjust it. The default is 20 minutes.
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| 76 | </p>
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| 77 | </dd>
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| 78 | </dlentry>
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| 79 | <dlentry>
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| 80 | <dt><codeph>--timesync-set-start</codeph>
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| 81 | </dt>
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| 82 | <dd>
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| 83 | <p>
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| 84 | Set the time when starting the time sync service.
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| 85 | </p>
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| 86 | </dd>
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| 87 | </dlentry>
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| 88 | <dlentry>
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| 89 | <dt><codeph>--timesync-set-on-restore</codeph> 0|1
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| 90 | </dt>
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| 91 | <dd>
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| 92 | <p>
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| 93 | Set the time after the VM was restored from a saved state
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| 94 | when passing 1 as parameter. This is the default. Disable
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| 95 | by passing 0. In the latter case, the time will be
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| 96 | adjusted smoothly, which can take a long time.
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| 97 | </p>
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| 98 | </dd>
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| 99 | </dlentry>
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| 100 | </dl>
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| 101 | <p>
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| 102 | All these parameters can be specified as command line parameters
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| 103 | to <codeph>VBoxService</codeph> as well.
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| 104 | </p>
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| 105 | </body>
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| 106 |
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| 107 | </topic>
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