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Timekeeping best practices for Linux guests (1006427)
Purpose
Resolution
Linux Timekeeping Best Practices
Notes:
- When both SMP and UP kernels are available, they must be applied to the appropriate SMP and UP virtual machines, otherwise a mismatch may cause time to drift.
- The recommended kernel parameters must be added to the kernel parameters already configured by the distribution.
32-bit Kernels
| Linux Flavor | Version | Kernel Parameters | Notes |
| RHEL | RHEL 6.x | No additional kernel parameters required. | |
| RHEL 5.8 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| RHEL 5.7 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| RHEL 5.6 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| RHEL 5.5 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| RHEL 5.4 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| RHEL 5.3 | divider=10 clocksource=acpi_pm | ||
| RHEL 5.2 | divider=10 clocksource=acpi_pm | ||
| RHEL 5.1 | divider=10 clocksource=acpi_pm | ||
| RHEL 5.0 | clocksource=acpi_pm | ||
| RHEL 4.9 | clock=pmtmr divider=10 hpet=disable |
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| RHEL 4.8 | clock=pmtmr divider=10 hpet=disable |
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| RHEL 4.7 | clock=pmtmr divider=10 hpet=disable |
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| RHEL 4.6 | clock=pmtmr hpet=disable |
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| RHEL 4.5 | clock=pmtmr hpet=disable |
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| RHEL 4.4 | clock=pmtmr hpet=disable |
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| RHEL 4.3 | clock=pmtmr hpet=disable |
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| RHEL 4.2 | clock=pmtmr hpet=disable |
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| RHEL 4.1 | clock=pmtmr hpet=disable |
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| RHEL 4.0 | clock=pmtmr hpet=disable |
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| RHEL 3 (All updates) | No additional kernel parameters required. | ||
| RHEL 2.1 | No additional kernel parameters required. | ||
| Redhat | Redhat 9.0 | No additional kernel parameters required. | |
| Redhat 8.0 | No additional kernel parameters required. | ||
| Redhat 7.3 | No additional kernel parameters required. | ||
| Redhat 7.2 | No additional kernel parameters required. | ||
| Redhat 7.1 | No additional kernel parameters required. | ||
| Redhat 7.0 | No additional kernel parameters required. | ||
| Redhat 6.2 | No additional kernel parameters required. | ||
| SLES | SLES 11 (All updates) | No additional kernel parameters required. | |
| SLES 10 SP4 on ESX 5.0 and later | clock=pmtmr hpet=disable |
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| SLES 10 SP4 on ESX 4.x | Use a VMI enabled kernel. | ||
| SLES 10 SP3 on ESXi 5.0 | clock=pmtmr hpet=disable |
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| SLES 10 SP3 on ESX 3.5 and 4.x | Use a VMI enabled kernel. | ||
| SLES 10 SP3 on ESX 3.0.x and earlier | clock=pmtmr hpet=disable |
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| SLES 10 SP2 on ESXi 5.0 | clock=pmtmr hpet=disable |
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| SLES 10 SP2 on ESX 3.5 and 4.x | Use a VMI enabled kernel. | ||
| SLES 10 SP2 on ESX 3.0.x and earlier | clock=pmtmr hpet=disable |
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| SLES 10 SP1 | clock=pmtmr hpet=disable |
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| SLES 10 | clock=pmtmr hpet=disable |
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| SLES 9 (All updates) | clock=pmtmr hpet=disable |
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| SLES 8 | No additional kernel parameters required. | ||
| SLES 7 | No additional kernel parameters required. | ||
| SLED | SLED 11 | No additional kernel parameters required. | |
| SLED 10 | clock=pmtmr hpet=disable |
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| SLED 9 | clock=pmtmr hpet=disable |
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| Suse Linux | Suse Linux 10.3 | clocksource=acpi_pm | |
| Suse Linux 10.2 | clocksource=acpi_pm | ||
| Suse Linux 10.1 | clock=pmtmr hpet=disable |
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| Suse Linux 10 | clock=pmtmr hpet=disable |
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| Suse Linux 9.3 | clock=pmtmr hpet=disable |
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| Suse Linux 9.2 | clock=pmtmr hpet=disable |
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| Suse Linux 9.1 | clock=pmtmr hpet=disable |
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| Suse Linux 9.0 | Remove desktop kernel command line parameter. | ||
| Suse Linux 8.2 | No additional kernel parameters required. | ||
| Suse Linux 8.1 | No additional kernel parameters required. | ||
| Suse Linux 8.0 | No additional kernel parameters required. | ||
| Suse Linux 7.3 | No additional kernel parameters required. | ||
| Ubuntu | Ubuntu 12.04 | No additional kernel parameters required. | |
| Ubuntu 11.10 | No additional kernel parameters required. | ||
| Ubuntu 11.04 | No additional kernel parameters required. | ||
| Ubuntu 10.10 | No additional kernel parameters required. | ||
| Ubuntu 10.04 | No additional kernel parameters required. | ||
| Ubuntu 9.10 | No additional kernel parameters required. | ||
| Ubuntu 9.04 with kernel 2.6.28-7.18 or later on ESX 4.0 or later | No additional kernel parameters required. | ||
| Ubuntu 9.04 with kernel prior to 2.6.28-7.18 on ESX 4.0 or later | Avoid using if possible. May cause guest operating system to stop responding. | ||
| Ubuntu 8.10 with kernel 2.6.27-12.28 or later on ESX 4.0 or later | No additional kernel parameters required. | ||
| Ubuntu 8.10 with kernel prior to 2.6.27-12.28 on ESX 4.0 or later | Avoid using if possible. May cause guest operating system to stop responding. | ||
| Ubuntu 8.10 | clocksource=acpi_pm | ||
| Ubuntu 8.04 on ESXi 5.0 | clocksource=acpi_pm | ||
| Ubuntu 8.04 on ESX 3.5 and 4.x | Use a VMI enabled kernel. | ||
| Ubuntu 8.04 on ESX 3.0.x and earlier | clocksource=acpi_pm | ||
| Ubuntu 7.10 | clocksource=acpi_pm | ||
| Ubuntu 7.04 | clocksource=acpi_pm | ||
| Ubuntu 6.10 | clock=pmtmr hpet=disable |
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| Ubuntu 6.06 | clock=pmtmr hpet=disable |
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| Ubuntu 5.10 | clock=pmtmr hpet=disable |
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| Ubuntu 5.04 | clock=pmtmr hpet=disable |
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| Mandriva | Mandriva Corporate Desktop 4.0 | clock=pmtmr hpet=disable |
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| Mandriva Corporate Server 4 | clock=pmtmr hpet=disable |
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| Mandriva Linux 2008 | clocksource=acpi_pm | ||
| Mandriva Linux 2007 | clock=pmtmr hpet=disable |
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| Mandriva Linux 2006 | clock=pmtmr hpet=disable |
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| Mandrake 10.1 | Does not support pmtmr. Avoid using if possible. | ||
| Mandrake 10 | Does not support pmtmr. Avoid using if possible. | ||
| Mandrake 9.2 | No additional kernel parameters required. | ||
| Mandrake 9.1 | No additional kernel parameters required. | ||
| Mandrake 9.0 | No additional kernel parameters required. | ||
| Mandrake 8.2 | No additional kernel parameters required. | ||
| Mandrake 8.1 | No additional kernel parameters required. | ||
| Mandrake 8.0 | No additional kernel parameters required. | ||
| Turbolinux | Turbolinux 10 Desktop | Does not support pmtmr. Avoid using if possible. | |
| Turbolinux 10 Server | clock=pmtmr hpet=disable |
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| Turbolinux Enterprise 8 | No additional kernel parameters required. | ||
| Turbolinux Workstation 8 | No additional kernel parameters required. | ||
| Turbolinux 7.0 | No additional kernel parameters required. | ||
| Asianux | Asianux Server 4 (all updates) | No additional kernel parameters required. | |
| Asianux 3.0 SP4 | No additional kernel parameters required. | ||
| Asianux 3.0 SP3 | No additional kernel parameters required. | ||
| Asianux 3.0 SP2 | No additional kernel parameters required. | ||
| Asianux 3.0 SP1 | No additional kernel parameters required. Use kernel 2.6.18-53.17AXS3 or later. | ||
| Asianux 3.0 | divider=10 clocksource=acpi_pm | ||
| CentOS | CentOS 6.x | No additional kernel parameters required. | |
| CentOS 5.8 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| CentOS 5.7 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| CentOS 5.6 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| CentOS 5.5 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| CentOS 5.4 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| CentOS 5.3 | divider=10 clocksource=acpi_pm | ||
| CentOS 5.2 | divider=10 clocksource=acpi_pm | ||
| CentOS 5.1 | divider=10 clocksource=acpi_pm | ||
| CentOS 5.0 | clocksource=acpi_pm | ||
| CentOS 4.9 | clock=pmtmr divider=10 hpet=disable |
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| CentOS 4.8 | clock=pmtmr divider=10 hpet=disable |
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| CentOS 4.7 | clock=pmtmr divider=10 hpet=disable |
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| CentOS 4.6 | clock=pmtmr hpet=disable |
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| CentOS 4.5 | clock=pmtmr hpet=disable |
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| CentOS 4.4 | clock=pmtmr hpet=disable |
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| CentOS 4.3 | clock=pmtmr hpet=disable |
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| CentOS 4.2 | clock=pmtmr hpet=disable |
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| CentOS 4.1 | clock=pmtmr hpet=disable |
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| CentOS 4.0 | clock=pmtmr hpet=disable |
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| Oracle | Oracle Linux 6.x | No additional kernel parameters required. | |
| Oracle Linux 5.8 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| Oracle Linux 5.7 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| Oracle Linux 5.6 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| OEL 5.5 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| OEL 5.4 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| OEL 5.3 | divider=10 clocksource=acpi_pm | ||
| OEL 5.2 | divider=10 clocksource=acpi_pm | ||
| OEL 5.1 | divider=10 clocksource=acpi_pm | ||
| OEL 5.0 | clocksource=acpi_pm | ||
| OEL 4.9 | clock=pmtmr divider=10 hpet=disable |
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| OEL 4.8 | clock=pmtmr divider=10 hpet=disable |
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| OEL 4.7 | clock=pmtmr divider=10 hpet=disable |
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| OEL 4.6 | clock=pmtmr hpet=disable |
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| OEL 4.5 | clock=pmtmr hpet=disable |
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| Debian | Debian 6.0 | No additional kernel parameters required. | |
| Debian 5.0 | No additional kernel parameters required. | ||
| Debian 4.x | divider=10 clocksource=acpi_pm |
64-bit Kernels
| Linux Flavor | Version | Kernel Parameters | Notes |
| RHEL | RHEL 6.x | No additional kernel parameters required. | |
| RHEL 5.8 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| RHEL 5.7 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| RHEL 5.6 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| RHEL 5.5 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| RHEL 5.4 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| RHEL 5.3 | notsc divider=10 nohpet |
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| RHEL 5.2 | notsc divider=10 nohpet |
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| RHEL 5.1 with RHSA-2007:0993-13 | notsc divider=10 nohpet |
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| RHEL 5.1 without RHSA-2007:0993-13 | notsc nohpet |
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| RHEL 5.0 | No additional kernel parameters required. | ||
| RHEL 4.9 | notsc divider=10 nohpet |
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| RHEL 4.8 | notsc divider=10 nohpet |
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| RHEL 4.7 | notsc divider=10 nohpet |
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| RHEL 4.6 | notsc nohpet |
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| RHEL 4.5 | notsc nohpet |
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| RHEL 4.4 | notsc nohpet |
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| RHEL 4.3 | notsc nohpet |
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| RHEL 4.2 | notsc nohpet |
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| RHEL 4.1 | nohpet | Does not support notsc. Avoid using if possible. | |
| RHEL 4.0 | nohpet | Does not support notsc. Avoid using if possible. | |
| RHEL 3 Update 9 with RHSA-2008-0973 | disable_lost_ticks | ||
| RHEL 3 through Update 8 | Has no workaround for lost tick overcompensation. Avoid using if possible. | ||
| SLES | SLES 11 (All updates) | No additional kernel parameters required. | |
| SLES 10 SP4 on ESX 4.0 and later | No additional kernel parameters required. | ||
| SLES 10 SP3 on ESX 3.5 and later | No additional kernel parameters required. | ||
| SLES 10 SP3 on ESX 3.0.x and earlier | notsc nohpet |
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| SLES 10 SP2 on ESX 3.5 and later | No additional kernel parameters required. | ||
| SLES 10 SP2 on ESX 3.0.x and earlier | notsc nohpet |
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| SLES 10 SP1 | notsc nohpet |
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| SLES 10 | notsc nohpet |
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| SLES 9 with kernel version 2.6.5-7.312 or later | ignore_lost_ticks nohpet |
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| SLES 9 with kernel version 2.6.5-7.311 or earlier | nohpet | Has no workaround for lost tick overcompensation. Avoid using if possible. | |
| SLED | SLED 11 | No additional kernel parameters required. | |
| SLED 10 | clock=pmtmr nohpet |
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| Suse Linux | Suse Linux 10.3 | clocksource=acpi_pm | |
| Suse Linux 10.2 | notsc nohpet |
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| Suse Linux 10.1 | notsc nohpet |
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| Suse Linux 10 | notsc nohpet |
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| Suse Linux 9.3 | notsc nohpet |
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| Suse Linux 9.2 | nohpet | Does not support notsc. Avoid using if possible. | |
| Suse Linux 9.1 | nohpet | Does not support notsc. Avoid using if possible. | |
| Ubuntu | Ubuntu 12.04 | No additional kernel parameters required. | |
| Ubuntu 11.10 | No additional kernel parameters required. | ||
| Ubuntu 11.04 | No additional kernel parameters required. | ||
| Ubuntu 10.10 | No additional kernel parameters required. | ||
| Ubuntu 10.04 | No additional kernel parameters required. | ||
| Ubuntu 9.10 | No additional kernel parameters required. | ||
| Ubuntu 9.04 with kernel 2.6.28-7.18 or later on ESX 4.0 or later | No additional kernel parameters required. | ||
| Ubuntu 9.04 with kernel prior to 2.6.28-7.18 on ESX 4.0 or later | Avoid using if possible. May cause guest operating system to stop responding. | ||
| Ubuntu 8.10 with kernel 2.6.27-12.28 or later on ESX 4.0 or later | No additional kernel parameters required. | ||
| Ubuntu 8.10 with kernel prior to 2.6.27-12.28 on ESX 4.0 or later | Avoid using if possible. May cause guest operating system to stop responding. | ||
| Ubuntu 8.10 | clocksource=acpi_pm | ||
| Ubuntu 8.04 with kernel 2.6.24-24.52 or later on ESX 4.0 or later | No additional kernel parameters required. | ||
| Ubuntu 8.04 with kernel prior to 2.6.24-24.52 on ESX 4.0 or later | Avoid using if possible. May cause guest operating system to stop responding. | ||
| Ubuntu 8.04 | clocksource=acpi_pm | ||
| Ubuntu 7.10 | clocksource=acpi_pm | ||
| Ubuntu 7.04 | No additional kernel parameters required. | ||
| Ubuntu 6.10 | notsc nohpet |
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| Ubuntu 6.06 | notsc nohpet |
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| Ubuntu 5.10 | notsc nohpet |
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| Ubuntu 5.04 | nohpet | Does not support notsc. Avoid using if possible. | |
| Mandriva | Mandriva Corporate Desktop 4.0 | notsc nohpet |
|
| Mandriva Corporate Server 4 | notsc nohpet |
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| Mandriva Linux 2008 | clocksource=acpi_pm | ||
| Mandriva Linux 2007 | notsc nohpet |
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| Mandriva Linux 2006 | notsc nohpet |
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| Mandrake Linux 10.1 | nohpet | Does not support notsc. Avoid using if possible. | |
| Turbolinux | Turbolinux 10 Desktop | nohpet | Does not support notsc. Avoid using if possible. |
| Turbolinux 10 Server | nohpet | Does not support notsc. Avoid using if possible. | |
| Asianux | Asianux Server 4 (all updates) | No additional kernel parameters required. | |
| Asianux 3.0 SP4 | No additional kernel parameters required. | ||
| Asianux 3.0 SP3 | No additional kernel parameters required. | ||
| Asianux 3.0 SP2 | No additional kernel parameters required. | ||
| Asianux 3.0 SP1 | No additional kernel parameters required. Use kernel 2.6.18-53.17AXS3 or later. | ||
| Asianux 3.0 | notsc nohpet |
||
| CentOS | CentOS 6.x | No additional kernel parameters required. | |
| CentOS 5.8 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| CentOS 5.7 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| CentOS 5.6 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| CentOS 5.5 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| CentOS 5.4 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| CentOS 5.3 | notsc divider=10 nohpet |
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| CentOS 5.2 | notsc divider=10 nohpet |
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| CentOS 5.1 | notsc nohpet |
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| CentOS 5.0 | No additional kernel parameters required. | ||
| CentOS 4.9 | notsc divider=10 nohpet |
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| CentOS 4.8 | notsc divider=10 nohpet |
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| CentOS 4.7 | notsc divider=10 nohpet |
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| CentOS 4.6 | notsc nohpet |
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| CentOS 4.5 | notsc nohpet |
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| CentOS 4.4 | notsc nohpet |
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| CentOS 4.3 | notsc nohpet |
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| CentOS 4.2 | notsc nohpet |
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| CentOS 4.1 | nohpet | Does not support notsc. Avoid using if possible. | |
| CentOS 4.0 | nohpet | Does not support notsc. Avoid using if possible. | |
| Oracle | Oracle Linux 6.x | No additional kernel parameters required. | |
| Oracle Linux 5.8 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| Oracle Linux 5.7 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| Oracle Linux 5.6 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| OEL 5.5 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| OEL 5.4 | No additional kernel parameters required. See the note below about the optional use of divider=10. | ||
| OEL 5.3 | notsc divider=10 nohpet |
||
| OEL 5.2 | notsc divider=10 nohpet |
||
| OEL 5.1 | notsc nohpet |
||
| OEL 5.0 | No additional kernel parameters required. | ||
| OEL 4.9 | notsc divider=10 nohpet |
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| OEL 4.8 | notsc divider=10 nohpet |
||
| OEL 4.7 | notsc divider=10 nohpet |
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| OEL 4.6 | notsc nohpet |
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| OEL 4.5 | notsc nohpet |
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| Debian | Debian 6.0 | No additional kernel parameters required. | |
| Debian 5.0 | No additional kernel parameters required. | ||
| Debian 4.x | notsc nohpet |
Recommended Configurations
These configurations are expected to have the best timekeeping behavior:- RHEL 6 32-bit or 64-bit running on ESX 4.0 or later
- RHEL 5.4 or later 32-bit or 64-bit running on ESX 3.5 or later
- SLES 10 SP2 or later 64-bit running on ESX 3.5 or later
- SLES 10 SP2 or later 32-bit running on ESX 3.5 or ESX 4.x
- SLES 11 32-bit or 64-bit running on ESX 4.0 or later
- Ubuntu 8.04 32-bit running on ESX 3.5 or later
- Ubuntu 8.04 or later 64-bit running on ESX 4.0 or later
- Ubuntu 8.04 or later 32-bit running on ESX 3.5 or ESX 4.x
VMI is supported in ESX 3.5 and ESX 4.x. Support for VMI is not present in ESX 5.0. For more information related to VMI enabled kernels, see:
- Enabling Virtual Machine Interface (VMI) in a Linux kernel and in ESX 3.5 (1003644)
- Enabling VMI with SLES10 SP2 32bit virtual machines on ESX (1005701)
- Best practices for running Java in a virtual machine (1008480)
- Time runs too fast in a Windows virtual machine when the Multimedia Timer interface is used (1005953)
Editing Kernel Configuration
Kernel command line parameters are specified in the /etc/lilo.conf or /boot/grub/grub.conf file, depending on your choice of boot loader.For LILO, put the kernel command line parameters at the end of the append line. For example, if the append line looks like:
append="resume=/dev/hda6 splash=silent"and you want to add clock=pmtmr divider=10, the updated text is:
append="resume=/dev/hda6 splash=silent clock=pmtmr divider=10"Remember to run /sbin/lilo after editing lilo.conf, so that your edits take effect.
For GRUB, put the kernel command line parameters at the end of the kernel line. For example if the kernel line looks like:
kernel /vmlinuz-2.6.18 ro root=/dev/hda2and you want to add clock=pmtmr divider=10, the updated text is:
kernel /vmlinuz-2.6.18 ro root=/dev/hda2 clock=pmtmr divider=10For additional information about working with boot loaders, see your Linux distribution's documentation.
NTP Recommendations
Note: VMware recommends you to use NTP instead of VMware Tools periodic time synchronization. NTP is an industry standard and ensures accurate timekeeping in your guest. You may have to open the firewall (UDP 123) to allow NTP traffic.This is a sample /etc/ntp.conf:
tinker panic 0
restrict 127.0.0.1
restrict default kod nomodify notrap
server 0.vmware.pool.ntp.org
server 1.vmware.pool.ntp.org
server 2.vmware.pool.ntp.org
driftfile /var/lib/ntp/drift
This is a sample (RedHat specific) /etc/ntp/step-tickers:
0.vmware.pool.ntp.org
1.vmware.pool.ntp.org
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.
Note: The directive tinker panic 0 must be at the top of the ntp.conf file.
It is also important not to use the local clock as a time source, often referred to as the Undisciplined Local Clock. NTP has a tendency to fall back to this 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 lines.
After making changes to NTP configuration, the NTP daemon must be restarted. Refer to your operating system vendor’s documentation.
VMware Tools time synchronization configuration
When using NTP in the guest, disable VMware Tools periodic time synchronization.To disable VMware Tools periodic time sync, perform one of these options:
- Set tools.syncTime = "FALSE" in the configuration file (.vmx file) of the virtual machine.
OR
- Deselect Time synchronization between the virtual machine and the host operating system in the VMware Tools toolbox GUI of the guest operating system.
OR
- Run the vmware-guestd --cmd "vmx.set_option synctime 1 0" command in the guest operating system. To enable time syncing again, use the same command with "0 1" instead of "1 0".
For ESX 4.1 and later, use these parameters for Linux, Solaris, and FreeBSD:
- To display the current status of the service:
vmware-toolbox-cmd timesync status
- To disable periodic time synchronization:
vmware-toolbox-cmd timesync disable
To do this for VMware ACE, VMware Fusion, VMware GSX Server, VMware Player, VMware Server, and VMware Workstation, run time synchronization software such as NTP or w32time in the host. For VMware ESX run NTP in the service console. For VMware ESXi, run NTP in the VMkernel.
Note: VMware Tools one-time synchronization events should not disabled.
Virtual Hardware clock configuration
When configuring the 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").For additional information, see Timekeeping in VMware Virtual Machines.
Note for uses on divider=10
For some operating systems, divider=10 is a supported kernel configuration option, but might not be necessary for accurate timekeeping. Using it reduces the frequency of timer interrupts by 10x, which reduces the CPU overhead of processing timer interrupts. This overhead is especially noticeable for idle virtual machines. The only drawback of using divider=10 is that the granularity of wakeups provided by the kernel changes from 1 ms to 10 ms. The vast majority of applications are not affected by this, but using divider=10 may not be the right tradeoff for some time sensitive applications. For some operating systems, specifically older versions, divider=10 greatly improves timekeeping accuracy and is strongly recommended.Additional Information
Tags
See Also
- Enabling Virtual Machine Interface (VMI) in a Linux kernel and in ESX 3.5
- Enabling VMI with SLES10 SP2 32bit virtual machines on ESX
- Time runs too fast in a Windows virtual machine when the Multimedia Timer interface is used
- Best practices for running Java in a virtual machine
- Linux ゲストの時刻管理のベスト プラクティス
- Melhores práticas de controle de horário para convidados Linux
- Las mejores prácticas de medición de tiempo para huéspedes Linux
- Linux系统时间同步最佳实践
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