Time sync on VirtualBox with Guest tools => VBoxService about dietpi-docs HOT 3 CLOSED

Actually I am investigating VBox with different timed sync options and their behaviour at "VBox machine reboot", "VBox machine sleep mode", "PC sleep mode with running VBox machine".

Basically, if you always shutdown your VBox machine, you do not have any problem.
Only in sleep mode situations where the PCs clock runs ahead from the VBox machine clock a time sync problem occurs. This problem can lead to apt update problems (with outdated files).

Depending on the results I assume that "daemon" will be the best recommendation. Results will be described in the installation chapter.

from dietpi-docs.

So VBoxService is running but not syncing the time with the host when exiting sleep mode? Looks like something we should ask at VBox forum. If I remember right, it should sync every 5 minutes drifting and every 20 minutes a full sync. But I'd expect it to sync directly on boot and as well after exiting any system mode where the system clock (or the service) stops.

from dietpi-docs.

Some results so far:

Behaviour

A.) Emulated RTC of the VM

Generally, there is a VM emulated RTC (read with hwclock) and a Linux system time (read with date) which basically run independent from each other.

These two clocks can be synchronized to each other with

• hwclock --systohc (equals to hwclock -w): The emulated RTC is set to the value of the Linux system time.
• hwclock --hctosys (equals to hwclock -s): The Linux system time is set to the value of the emulated RTC).

B.) Behaviour in regard of vboxadd-service

1. Without vboxadd-service running (i.e. without VirtualBox Extensions installed)
   • Setting in dietpi-config to all options except Custom works like expected
2. With vboxadd-service running
   • Having options except Custom leads to an error in systemctl status systemd-timesyncd, also at boot time a timeout for the timesync occurs.
     Stopping then the vboxadd-service (at least removing the symbolic link /usr/sbin/VBoxService which links to /opt/VBoxGuestAdditions-6.1.18/init/vboxadd-service) helps to run options except Custom.
     (Remark: The symbolic link can also be added manually via ln -s /opt/VBoxGuestAdditions-6.1.18/init/vboxadd-service /usr/sbin/VBoxService)
   • t.b.d. What happens if option Custom is set?

C.) Behaviour at suspend/resume (i.e. no shutdown of the LInux system)

General: The hwclock (as well as the system time) is halted and gets a delay to the host PCs time.

Due to VirtualBox's documentation there should be the ability to activate/deactivat the clock time takeover (which time?) at the resume process via
VBoxManage guestproperty set <VM-name> "/VirtualBox/GuestAdd/VBoxService/--timesync-set-on-restore" 0|1

1. Without vboxadd-service running (i.e. without VirtualBox Extensions installed)

   • Setting in dietpi-config to all options except Custom works like expected
     • If set to option 1 (boot only): No time is corrected after resume
     • If set to option 2, 3: Linux system time is set after 1 hour resp. 1 day (emulated RTC also changed)
     • If set to option 4: Time is set in about 2 minutes after resume (emulated RTC not changed)
   • Generally the fake-hwclock updates the emulated RTC hourly (updates at option 4).

2. With vboxadd-service running
   T.b.d.

Structural views

Structural view without Guest additions

Structural view with Guest additions (in work)

@MichaIng: Is the description above o.k.?

from dietpi-docs.