ntp server on Proxmox VM

[CAHEKs]

I have VM with standart ntp server. (debian ntp ) It sync with external ntp.pool.org.
Node sync with this VM. What true practice for this case? (Option use rtc local time set :NO)

 

[aaron]

Node sync with this VM.

This is a bit of a circular dependency and not the best idea. Should not be much of a problem on a single node, but in a cluster with services that depends on a synchronized clock (e.g. Ceph), I would keep the NTP source outside the cluster.

What true practice for this case? (Option use rtc local time set :NO)

This option only defines if the virtual HW clock of the VM should be set to the local timezone or UTC. Linux, and other UNIX (likes), keep their HW clock at UTC and calculate the time shown to the local timezone. Windows on the other hand, keeps the HW clock to the local timezone. Therefore, this option's default behavior depends on the selected guest OS type.

For your use case, this is quite unimportant, and you should leave it as is and set the guest OS type correctly

 

[CAHEKs]

I think that Proxmox or kvm have mechanism to change time virtual HW clock of the VM from node clock.
If it's true, how disable it ?

 

[aaron]

The (emulated) HW clock is important as it gives the OS a time during startup (can be set manually if needed: RTC start date parameter). While an OS is running, it is not relying on the HW clock but will use the "system clock".
You can sync the time between the HW and system clock in either direction with the hwclock tool under Linux.

Once the VM is booted, there should not be any interference with the VMs clock from the hypervisor side.