Linux – How to disable time sync in a VMWare guest

clocklinuxvirtual machinevmware

I have a desktop (centos 6) that has a VM guest (RedHat 5.5).

I just try to set the date to past time in VM guest. And it works.

However, after 50 minutes, the time is sync to current time.

After I check with the cron job, I did not find any cron job to do the time sync.

May I know how can I disable the time sync in the VM guest?

Edited: I am using virsh to start and stop VM guest.

Best Answer

If you are running VM tools, the tool has an option to periodically sync the time with the host.

If in your path: vmware-toolbox-cmd timesync status to view and vmware-toolbox-cmd timesync disable to stop it.

Of course any non-vm method of time sync could be there as well. If the system starts ntpd, it may be syncing that way. You could run ntpd -q to see if the system responds with associations. If so, it will probably sync with them. You'd then want to disable ntpd.

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Ubuntu – Calls to sync/fsync slow down after 30 minutes uptime

The symptoms are very consistent with a mostly saturated IO system, however having for the most part ruled out IO load from the OS/userspace side, another possibility is the drive running self-tests on itself, which may include reading from all the sectors. This should be queryable/tunable from smartctl (At least one place being smartctl -c for querying).

As for why it's coming and going and started suddenly now:

The drive has passed a certain stage in it's life (number of sectors written, time spun up, etc.) and the firmware on the drive have triggered one of these scans
I believe this also can be triggered via smartctl, so it's possible some automated process triggered it
Having one of these scans triggered and flagged as either in progress or started, when the drive has spent a certain amount of time powered on, it's re-triggered either from the beginning or to resume where it left off

Linux – NTP time sync takes a long time

The rpi does not have an RTC, and so it boots always in 1 Jan 1970 - the time to put the server and NTP synchronised slowly and incrementally is bigger; so by default NTP does not start operating normally until the difference between NTP and the system is corrected.

I would add to your ntp.conf file as the first line (it has to be the first line):

tinker panic 0

This setup is advised for VMs and iOTs devices.

tinker panic - Specifies the panic threshold in seconds with default 1000 s. If set to zero, the panic sanity check is disabled and a clock offset of any value will be accepted.

I would also consider buying an RTC, as it is cheap, especially if you intend to have projects without Internet connectivity. see hwclock can't open rtc file

Best Answer

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